See discussions, stats, and author profiles for this publication at: https://www.researchgate.

net/publication/352394416

West Texas (Permian) Super Basin, United States: Tectonics, structural

development, sedimentation, petroleum systems, and hydrocarbon
reserves

Article in AAPG Bulletin · June 2021

DOI: 10.1306/03042120130

CITATIONS READS

21 8,276

3 authors, including:

Bill Fairhurst
Riverford Exploration LLC
26 PUBLICATIONS 44 CITATIONS

SEE PROFILE

All content following this page was uploaded by Bill Fairhurst on 15 November 2021.

The user has requested enhancement of the downloaded file.

 West Texas (Permian) Super AUTHORS

Basin, United States: Tectonics, Bill Fairhurst ~ Riverford Exploration,

LLC, Spring, Texas; bfairhurst@riverford-
resources.com
structural development, Bill Fairhurst is president and cofounder of

sedimentation, petroleum Riverford Exploration, LLC. He has been a

technical lead and senior executive for the past
25 years at several independent oil and gas
systems, and hydrocarbon firms, including Riverford, Petro-Hunt, Eagle,
and Hilcorp, after 15 years at Marathon, and
reserves was recently a principal investigator and
project manager at the Bureau of Economic
Geology. He and his teams have made dozens
Bill Fairhurst, Tom Ewing, and Bob Lindsay of discoveries throughout the United States,
including opening the economic development
of the Wolfbone play in the Delaware Basin.
He earned an M.B.A. from the University of
ABSTRACT
Houston, an M.S. from the University of
The West Texas (Permian) Super Basin is the prototype super Missouri, a B.A. from Ohio Wesleyan
basin. The basin has produced 28.9 billion bbl of oil and 203 TCF University, is a Certified Petroleum Geologist,
of gas (63 billion BOE, 1920–2019). The US Geological Survey and is a Licensed Professional Geologist in the
and Bureau of Economic Geology estimate this super basin has state of Texas.
remaining reserves of 120–137 billion BOE, twice the volume Tom Ewing ~ Frontera Exploration
produced during the first 100 yr of hydrocarbon production. Consultants, San Antonio, Texas; tewing@
During the past decade, the West Texas Super Basin has been the fronteraexploration.com
driver of production growth in the United States and has decades Tom Ewing is an independent consulting
of remaining economic production and reserve growth. geologist and partner at Yegua Energy
The West Texas Super Basin is a complex Paleozoic basin Associates. He explores for hydrocarbons
built on a varied Proterozoic crust. After Cambrian rifting, regional and conducts regional studies in Texas and
subsidence began in the Middle Ordovician and continued into the elsewhere, seeking to understand the geologic
Devonian, forming the To bosa Basin. The early Paleozoic To bosa history of Texas and the Gulf of Mexico,
emphasizing the tectonics of Texas
Basin subsidence terminated during Mississippian epeirogenic
and adjoining states, Cenozoic sequence
uplift. A later stage of subsidence began in the Late Mississippian stratigraphy, Mesozoic regional stratigraphy,
accompanied by large-scale faulting and moderate folding. This and surface–subsurface relationships in
tectonic and structural development was controlled by basement central Texas. He received his Ph.D. from the
terrains, earlier tectonic, and structure reactivated by compression of University of British Columbia.
the Ancestral Rocky Mountains and Marathon-Ouachita orogenic
Bob Lindsay ~ Lindsay Consulting, LLC,
events. These formed the Permian Basin. The Marathon-Ouachita Midland, Texas; lindsayconsulting2016@
tectonic event ended in the Wolfcampian (early Permian). Subsidence gmail.com
continued to the end of the Permian (Ochoan). Periodic subsidence
Bob Lindsay spent 39 years in the petroleum
during the Mesozoic was likely caused by Rocky Mountain industry. He received his B.S. from Weber State
(Laramide) deformation. Cenozoic (late Paleogene–Neogene) College (1974), M.S. from Brigham Young
western uplift tilted the basin to the east. Each of these events has University (1976), and Ph.D. from University of
a significant influence on the basin petroleum systems. Aberdeen, Scotland (2014). He worked for Gulf
Oil, Chevron, ChevronTexaco, and Saudi
Aramco in production, exploration, enhanced
Copyright ©2021. The American Association of Petroleum Geologists. All rights reserved.
recovery, and applied research, working on
Manuscript received August 10, 2020; provisional acceptance October 15, 2020; revised manuscript
conventional, tight, and unconventional
received October 22, 2020; final acceptance November 3, 2020. reservoirs. He applies outcrop studies to
DOI:10.1306/03042120130

AAPG Bulletin, v. 105 no. 6 (June 2021), pp. 1099–1147 1099

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 subsurface reservoir studies. Following The basin has multiple source rocks and petroleum systems
retirement in 2015, he consults, runs field trips, formed during various stages of basin development. During the
and teaches at Brigham Young University. formation of the early Paleozoic Tobosa Basin, Simpson Group
and Woodford Shale source rocks were deposited. During the
ACKNOWLEDGMENTS transitional basin development phase, the Barnett Shale source
rocks were deposited, and during Permian Basin subsidence, the
The authors wish to acknowledge this
research support from their consulting Wolfcamp and middle Permian (Leonardian and Guadalupian)
practices, clients, and producing companies source rocks were deposited. Continued subsidence into the
Riverford Exploration, LLC; Frontera Mesozoic resulted in the deposition of additional strata. These
Exploration Consultants; and Lindsay Mesozoic intervals are now mostly eroded but provided sufficient
Consulting, LLC. Special appreciation is given burial depths for thermal development and increased the extent
for the support, research, and publications by of thermal effect for maturation and migration of hydrocarbons
the Bureau of Economic Geology, Jackson within these Paleozoic petroleum systems.
School of Geosciences, The University of
Leonardian and Guadalupian conventional reservoirs have
Texas at Austin. The Tight Oil Resource
Assessment (TORA) Industrial Consortium produced 71% of the resources from all conventional West Texas
at the Bureau of Economic Geology is Super Basin reservoirs. These reservoirs are typically most abundant
highlighted here and supported this research. on the shelf crest (shelf to edge), where reservoir development is
The original industry members of the TORA maximized and becomes a focus of hydrocarbon migration from the
Consortium are Concho, Energen, Parsley deeper Delaware and Midland Basins source rocks and shallower,
Energy, Pioneer Natural Resources, Total, more-proximal shelf and platform source rock systems.
Sequitur Energy Resources, SM Energy, Unconventional resource reservoir oil production in the West
University Lands, and the State of Texas
Texas Super Basin accounted for just under 90% of total basin
Advanced Oil and Gas Resource Recovery
daily production at the close of the last decade (2010–2019). Total
Program. Other members for 2 or more
years since TORA’s initial program are West Texas Super Basin production peaked in March 2020 at 4.7
Ameredev, Apache, BMO Capital Markets, million BOPD. Since that time, production has declined because
Covia, Endeavor, Equinor, ExxonMobil, of lower rates of investment driven by lower product prices.
Fairfield, Ikon Science, Inpex, Ovintiv, The West Texas Super Basin economic oil and gas production
Quantum Energy, Schlumberger, Shell, and has benefited from an extensive infrastructure, a large geologic and
Thunder Exploration. This work has been engineering community, regulatory and public support, open ac-
enhanced by the AAPG super basin editors cess, sufficient capital availability, and a scalable service industry.
Charles Sternbach, Claudio Bartolini, and
The paradigm toward new drilling, completion, and production
AAPG Editor Robert K. Merrill. Reviewers
Andy Pepper, Mike Party, and Bill DeMis technology has been driven by unconventional resource reservoir
provided clarity and useful interaction during development in the basin. These West Texas Super Basin tech-
final manuscript preparation. Their assistance nological developments have lead industry technology for uncon-
is most appreciated. ventional resource development worldwide. Maintaining talented
human resources and capital are challenges that time will tell if
individual firms and the industry will meet to develop the hydro-
carbon resources within the basin.

INTRODUCTION

The West Texas (Permian) Super Basin is the prototype super

basin. To be considered a super basin, the following criteria
have been established: (1) one or more petroleum systems, some
linked to other regions or continents; (2) geologic architec-
ture and timing of petroleum systems for generation, migration,
and entrapment of reserves; (3) production of 5 billion BOE and
having 5 billion BOE remaining recoverable reserves; (4) many

1100 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 pays and plays; (5) substantial infrastructure includ- der Gracht, 1929; Ver Wiebe, 1929) and more re-
ing geologic community, regulatory and public sup- cently (King, 1977; Ewing, 2019; Fairhurst and Lindsay,
port, open access, investment incentives, scalable 2020) represents the entire area, tectonic history,
service industry; (6) talented human resources and and stratigraphic units from Cambrian through
capital; and (7) super basin thinking, a paradigm to- present day (Figure 2). The term Permian Basin is
ward new technology in an existing basin (Whaley, explicitly referenced to the basin geologic record and
2019; Fryklund and Stark, 2020; Sternbach, 2020). stratigraphic units of that system (the Permian
The introduction, other topical, and specific super System). The current basin outline for the West
basin papers presented in this compendium include Texas (Permian) Super Basin (Figure 1) is only valid
all or most of these criteria. Each of these criteria is and developed during the Late Mississippian into
recognized within the West Texas Super Basin; most the Triassic. Throughout most of the geologic his-
are discussed and presented. tory of the West Texas Super Basin, it had a much
The development of super basin thinking, new different basin architecture controlled by a varied
concepts by petroleum geologists resulting in new tectonic development, sedimentary processes, and
technologies to extract hydrocarbons from the West stratigraphic events before and after the Permian.
Texas Super Basin by petroleum geologists and Additionally, there are many interrelated controls
engineers, has rejuvenated industry investment and (i.e., temporal, spatial, stratigraphic, and tectonic)
economic activity in the basin. These developments necessary for understanding the West Texas Super
have been the controlling supply-side factor for Basin petroleum systems. For these reasons and clas-
world-oil price for almost a decade and the primary sification as a super basin, the term West Texas Super
focus of domestic investment for onshore oil and gas Basin is preferred.
production and reserve growth (Fairhurst, 2019, 2020,
2021).
The West Texas Super Basin covers more than TECTONIC AND DEPOSITIONAL HISTORY
57,500 mi2 (Figure 1), including more than 50
counties in west Texas and 5 counties in southeastern The West Texas Super Basin is a complicated Pa-
New Mexico. The basin structure covered a much leozoic basin, built on a varied Proterozoic crust
larger geographic extent during various geologic ages, subjected to only limited Mesozoic and Cenozoic
and sedimentation occurred over a much larger area. modification, primarily along the basin margins (Ewing,
These structural and stratigraphic boundaries are dif- 2019). The West Texas Super Basin remained undis-
ficult to define within a single age, let alone throughout covered for decades after the first geological studies of
basin development. For example, the eastern bound- west Texas. Before 1920, the basin was defined in only
ary of the basin most commonly used (Figure 1) is the very simple geologic concepts from fieldwork and re-
eastern shelf edge, the approximate position shown ports by The University of Texas Mineral Survey, later
was the shelf edge only during the early Wolfcampian to become the Bureau of Economic Geology, and then
(Brown et al., 1987, 1990; Dutton et al., 2005a, b). by industry (Phillips, 1901, 1902; Richardson, 1904;
The eastern shelf of the basin continues to the Bend Udden, 1915, 1917; Udden et al., 1916; Böse, 1917;
arch, the axis of that feature being 150 mi farther east Beede, 1918a, b; Liddle, 1918; Liddle and Prettyman,
with the eastern shelf typically treated as a separate 1918; Pratt, 1921; King, 1942, 1948; Fairhurst and
geologic providence. The western part of the eastern Lindsay, 2020). Drilling and production during the
shelf, proximal to the Midland Basin eastern margin, second half of the 1920s identified the thick package
is included in this study because of the associated of marine Permian rocks in the subsurface, in which
tectonic, sedimentological history, and production prolific oil fields developed. Subsequent, deeper drilling
dominantly from conventional reservoirs. The fea- discovered large structures (uplifts and basins) and thick
tures illustrated in Figure 1 and the stratigraphic Pennsylvanian and older Paleozoic rocks that hosted
column (Figure 2A, B) provided the framework for large oil and gas reserves. As discussed by King (1977, p.
the reservoirs, production, and reserves presented. 38), “Amazingly, as has happened with many other
The West Texas Basin as it was first referenced great scientific discoveries, nearly every geologist who
(Udden, 1915; Powers, 1927; van Waterschoot van was working in west Texas came independently to the

Fairhurst et al. 1101

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 1. Map showing outline of the West Texas Super Basin area and locations of basins and platforms during the late Permian. Also
shown are important outcrop locations of Permian-age strata. From Ruppel (2019a); modified from Dutton et al. (2005a, b; used with
permission from AAPG).

1102 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 same conclusion at about the same time, by 1929 the Neogene uplift and rhyolitic volcanism associated with
“reef theory” as an explanation of the Permian stratig- basin and range extension to the west, and, finally,
raphy of the region.” The component parts, namely, the regional uplift of western North America (King, 1977;
Delaware Basin, Midland Basin, and central basin axis, the Alvarado ridge of Eaton, 1987).
were then recognized (Fairhurst and Lindsay, 2020; A regional structure map on top of the Lower
Figure 1). Ordovician Group, Ellenburger (Figure 4) shows the
The basin contains only limited outcrops, mostly composite basin present configuration. The purple,
in the western and southern mountains, with more brown, and rose areas in Figure 4 include thick
limited outcrops along the northern and eastern Permian rocks caused by late Paleozoic subsidence. As
basin margins. The Guadalupe Mountains to the we see it today, the basin consists of a deep trough
west and Glass Mountains to the south provide running south-southeast from southeastern New
excellent outcrops of the thick Permian section, Mexico, the northern Delaware Basin, with Malaga
which are partial analogues for the Permian strata and Round Mountain subbasins. Just north of the
drilled and productive in the basin. Because of the Mexican border, the southern Delaware Basin veers to
limited outcrop, especially of lower and middle the southeast into the Val Verde Basin. To the
Paleozoic strata, and lack of high-quality seismic northeast is a complex, generally high-standing area
reflection data until recently, tectonic models for the called the central basin axis (or uplift), which rises to
basin have been widely divergent. Ewing (2019) the south to the Fort Stockton uplift. The central basin
provides a recent interpretation of the complete axis formed the pedestal for a Permian carbonate
tectonic history for the basin. Better, higher-quality platform, the “central basin platform.” To its northeast
two-dimensional and three-dimensional (3-D) seismic is the shallower Midland Basin. A complex system
data, other geophysical methods of investigation, of faults covers the central basin axis and extends
core, subsurface wellbore interpretation, detailed westward through the Delaware Basin and eastward
outcrop, and regional studies allow a better under- through the western Midland Basin. The south-
standing of basin history as the basis for all petroleum western and southern boundaries of the Delaware–Val
systems modeling. Verde trough are complex and poorly understood.
The long basin history is best illustrated by a one- They include a broad uplift to the west, the Diablo
dimensional (1-D) subsidence model near the basin uplift, and the Devils River uplift to the southeast.
center, Toyah Lake field near Pecos, Texas (Figure Thrust sheets of the Marathon orogeny overlie the
3). After Cambrian rifting, a regional subsidence trough to the south; the southern termination of the
event began in the Middle Ordovician and contin- trough is unknown beneath the overthrust Marathon
ued with decreasing rates into the Devonian. The fold–thrust belt.
Tobosa Basin (Galley, 1958) subsidence was termi- The West Texas Super Basin central basin axis
nated by epeirogenic uplift, especially in the eastern (or uplift) is commonly referenced as the central
part of the basin, succeeded by Mississippian subsi- basin platform. Emphasis and clarification are made
dence. The main stage of basin subsidence began in to distinguish the central basin axis, a tectonic and
the Late Mississippian. It was accompanied by large- structural feature, from the central basin platform, a
scale faulting and some folding controlled by basement Permian sedimentary-stratigraphic feature.
terrains, earlier tectonic and structure reactivated by
tectonic compression formed by Ancestral Rocky
Mountains (ARM), and Marathon-Ouachita orogenic Proterozoic Basement Terranes and
events. These tectonic events continued through Boundaries
the Pennsylvanian and ended in the Wolfcampian
(early Permian), with subsidence continuing into the The West Texas Super Basin is constructed on Pro-
late Permian, post-ARM subsidence. Post-Paleozoic terozoic continental crust of 35–55 km thickness.
history is episodically recorded, with Triassic subsi- The assembly of this area is complex and is still not
dence in the northern and eastern part of the basin, fully understood. Ewing et al. (2019) provide a com-
significant regional Cretaceous subsidence likely (but plete discussion and references. The northwestern part
with most of the evidence eroded), significant of the basin lies above a complex, layered crust, where

Fairhurst et al. 1103

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 2. Stratigraphic column for the West (W) Texas Super Basin modified from Ruppel (2019a) and used with permission from AAPG.
(A) Permian system. (B) Cambrian through Carboniferious systems. L. = Lower; NW = Northwest; Sp. = Spring; U. = Upper.

1104 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 2. Continued.

Fairhurst et al. 1105

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 3. Total sediment accumulation history for the Phanerozoic for the Toyah Lake field near Pecos, Reeves County, Texas (see
Figure 11A for location), at the center of the Tobosa Basin subsidence in the Delaware Basin (southern Malaga subbasin) from Ewing
(2019, used with permission from AAPG). Time scale is geologic time scale (GTS) 2012 (Gradstein et al., 2012). elev. = elevation; Guad. =
Guadalupian; L = Lower; M = Middle; MISS. = Mississippian; Ordov. = Ordovician; PENN. = Pennsylvanian; U = Upper.

the pre-1600 Ma crust of the Mazatzal orogeny is Two significant features lie more or less on the
overlain by rhyolitic volcanic rocks and intruded by border between the two areas. In north Texas, mag-
related granites of 1380–1320 Ma age (Figure 5). netic lineations show a northeast-trending front with a
These form the southern granite–rhyolite province magnetic signature similar to the Grenville front in
and are intruded by 1165–1100 Ma–aged mafic dikes Canada. This is inferred to represent the northwestern
and sills. Some juvenile crust of 1470–1350 Ma age is extent of crustal reworking because of the 1100 Ma
indicated to the east and south (Bickford et al., 2015). Llano orogeny, part of the Grenville orogenic system.
Sedimentary rocks of the De Baca sequence (ca. Trending east-northeast is a pronounced gravity low
1250 Ma) overlie the rhyolites. These rocks are ex- called the Abilene gravity minimum (Adams and
posed northwest of Van Horn and in El Paso. The Keller, 1996). This linear feature extends north of
southern part of the basin is constructed on rocks Van Horn across the northern Delaware and Mid-
inferred from the Llano orogeny, as exposed in the land Basins eastward past Abilene nearly to Fort
Llano window in central Texas. Llano, protoliths of Worth. This feature has been interpreted to rep-
sedimentary (and volcanic?) rocks of 1288–1232 Ma resent a granitic batholith, responding to an arc of
age were deeply buried and locally metamorphosed post-1350 Ma age, perhaps associated with Llano
to eclogite facies ca. 1140 Ma, then metamor- protolith deposition. The Abilene minimum crosses
phosed to amphibolite grade at midcrustal depths ca. the Llano front as derived from magnetic anomalies,
1115 Ma, related to accretion of an older volcanic arc such that the eastern half is likely reworked during
from the south. The metamorphic complex was then the Llano orogeny.
uplifted to 10 km and intruded by a large granite The only exposure of Proterozoic rocks in the
volume at ca. 1080 Ma (Town Mountain Granite), basin area lies near the city of Van Horn. The southern
which now covers 40% of the exposed area. half of the outcrop, Carrizo Mountain Group, consists

1106 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 4. Structure map contoured on top of Ellenburger Group carbonates (Lower Ordovician) from Ewing (2019, used with per-
mission from AAPG) based on Gardiner (1990), Ewing (1991), and Shumaker (1992). Colors represent depth ranges below sea level in
5000-ft increments; contour interval = 1000 ft. CH = Mexican state of Chihuahua; CO = Mexican state of Cohuila; FT = Fort; NM = New
Mexico; RCSM = Rojo Caballos–San Martine fault zone; TX = Texas; T.Z. = transverse zone.

of 1350 Ma metarhyolite and metasediment, southern zircons of 1130 Ma (Mulder et al., 2017). However,
granite–rhyolite province, deformed and metamor- the Streeruwitz thrust movement appears to be
phosed to greenschist to upper amphibolite facies. 1060–980 Ma in age, one of the youngest Proterozoic
Subsequently, this terrain thrust northward over sed- compressional events in the region. If correct, the
iments of the 1240–1260 Ma–aged De Baca terrane, Hazel may be younger than indicated by detrital
Allamoore. To the north, a thick alluvial sequence was zircons.
deposited, the Hazel Formation, 2500 m (8200 ft), At the approximate time of the Llano meta-
which yields a maximum depositional age from detrital morphism and deformation (1100 Ma), west Texas

Fairhurst et al. 1107

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 5. Basement terranes and Cambrian tectonic elements and ages from Ewing (2019) and Ewing et al. (2019, used with permission
from AAPG). CMG = Carrizo Mountain Group; EP = El Paso; gr = granite; Lt Pz = Late Paleozoic; PD = Packsaddle domain; Sm-Nd =
samarium-neodymium isotope radiometric age date; Ss = sandstone; VSD = Valley Spring domain; VH = Van Horn.

experienced extension and complex igneous activity. Adams and Keller, 1996). High-amplitude gravity
At El Paso, a granitic intrusion and coeval ash-flow highs extend from this area north-northwest to the
rhyolite cap were emplaced at ca. 1120 Ma. On the Hobbs area, the Hobbs complex (most extensive
Fort Stockton uplift (south of the Pecos intrusive of the Pecos intrusive complex illustrated on the
complex areas illustrated), the North American 1 Texas–New Mexico border), suggesting a regional
Nellie well penetrated a thick layered mafic–ultra- extent to the mafic complex. Isolated gravity highs
mafic complex, the Pecos intrusive complex, which farther north and northeast probably represent sim-
yielded a gabbro age of 1163 Ma (Keller et al., 1989; ilar intrusions, either mafic or mafic rooted. Coeval

1108 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 basaltic sills are widespread in the northernmost basin disclosed several thousand feet of metarhyolite or
and north into the Texas panhandle, the Swisher metasedimentary rock beneath Paleozoic carbonate
diabase, with a 1081 Ma zircon date near Amarillo. and overlying Llano-orogeny–age metamorphic and
The major Proterozoic features that are reflected granitic rocks (Nicholas and Waddell, 1989). These
in the basin architecture of the Paleozoic basin are units are variously dated at ca. 700 Ma and ca.
the deeply layered and complex crust of the northern 530–480 Ma by Rb–Sr isotope dating (Denison et al.,
basin, which may affect the scale and vergence of 1977; Nicholas, 1983), but recent work has found a
structures in the area; the northeast-trending Llano detrital zircon signature with a maximum depositional
front, which appears to have been slightly reactivated age of 533–545 Ma and abundant 820–570 Ma grains
in places; and foremost, the Pecos complex gravity (Rodriguez et al., 2017). This province’s extent is
high, which underlies the central basin axis and is unknown, but it may extend beneath the Val Verde
likely to have been a primary driver for intracratonic and southern Delaware Basins. Near Van Horn, a
subsidence (lower to middle Paleozoic), localizing sedimentary graben-filling unit, the Van Horn sand-
ARM–Marathon-Ouachita deformation, and perhaps stone, has yielded detrital zircons with a maximum
middle–late Permian subsidence. depositional age of 535 Ma (Spencer et al., 2014). It is
likely that much of the northwest to west-northwest
structural grain in the West Texas Super Basin was
Cambrian Extension: The Breakup of generated or activated in this Cambrian event, as is the
Rodinia case of the Oklahoma aulacogen generating the struc-
tural grain in Oklahoma and the Texas panhandle.
After the Llano orogeny, part of the Grenville sys- Reactivation of these structural grains occurs through-
tem, Laurentia, North America, was joined to the out the multiple Paleozoic tectonic events.
supercontinent Rodinia. The Laurentia southern After rifting ceased at ca. 530 Ma, the Laurentian
margin was rifted and separated from other conti- crust cooled and subsided. Upper Cambrian and
nental blocks in the latest Proterozoic and Cambrian Lower Ordovician strata thicken markedly eastward
(ca. 700–535 Ma) and was the last part of Laurentia and southward to the continental margin near San
to detach. The record of this event in Texas consists Antonio, perhaps indicating the location of Cam-
of two west-northwest trending axes of extension, brian high heat flow, igneous activity, and extension.
magmatism, and the deeply buried margin of rec- By the Early Ordovician, a carbonate platform ex-
ognizable Proterozoic crust in the south and central tended across the entire area, the Ellenburger Group,
parts of the state (Figure 5). To the north and with little evidence of West Texas Super Basin
northeast, the southern Oklahoma aulacogen is well subsidence. The relative lack of thickening into the
known and studied, because it is extensively exposed Delaware aulacogen contrast with the extensive
where it has been uplifted by late Paleozoic orogene- thickening of the Arbuckle Group into the south-
sis (Fritz and Mitchell, 2021, this issue). In that trend, ern Oklahoma aulacogen (Fairhurst, 2016, 2018;
early mafic magmatism of >552 Ma age is succeeded Fairhurst and Rogers, 2018).
by large volumes of granitic magma forming plutons
at shallow depth and erupted rhyolite flows at ca.
539–515 Ma. (Hanson et al., 2013; Ewing, 2016). Tobosa Basin: Intracratonic Subsidence
This zone is interpreted to represent either a failed
arm of rifting or a leaky transform-parallel fault sys- The Tobosa Basin subsidence began in the Middle
tem (Thomas, 2014; Fairhurst, 2016, 2018) associ- Ordovician. Subtle evidence of Early Ordovician
ated with successful rifting to the southeast that Tobosa Basin subsidence exists, provided in other
detached a crustal block and may have formed oce- sections, but not as clearly defined as the Middle
anic crust. Ordovician to Mississippian (Visean). By the
A similar but less studied arm occurs in south- Mississippian, up to 1500 m (5000 ft) of sediment
west Texas, the Delaware aulacogen (Walper, 1977; had been deposited and preserved from erosion in
Fairhurst, 2016, 2018), where it is mostly buried. a broadly oval area centered just southwest of the
Samples from wells drilled on the Devils River uplift southeastern corner of New Mexico in what is

Fairhurst et al. 1109

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 now in the deeper part of the Delaware Basin in represented (shape and areal extent). The Simpson
that area. A likely source for the Tobosa Basin Group isochore outline (Figure 6) is reasonably
subsidence is the failure of the Delaware aulacogen equivalent to the 100-ft Woodford isochore value.
and subsidence caused by the high-density Pecos- Figure 7 includes an overlay of the Permian Basin
Hobbs mafic complex compared to the less-dense tectonic elements for comparison and later discussion.
granite and rhyolite crust (Figure 5). The thickest Woodford at the Tobosa Basin center is
The Tobosa Basin is separated from the Ana- roughly spatially equivalent to the later developed
darko Basin (north Texas and Oklahoma) to the (Permian) Malaga subbasin (Figure 4). The Woodford
northeast by the Texas arch, a broad area of episodic on the (Permian) northwest shelf and the northern
erosion extending from northern New Mexico to shelf, and in the Midland Basin is typically less than
central Texas. In the Llano area, thin remnants of 100 ft thick and does not extend onto the (Permian)
Ordovician, Silurian, and Devonian strata are preserved eastern shelf.
in karstic sinkholes developed on the underlying El- Multiple organic-rich source rocks are deposited
lenburger. The Llano uplift began with mid-Ordovician in North America in numerous tectonic basin types
inversion of a previously thickened Cambrian to El- associated with this Late Devonian transgression
lenburger wedge of sediment, possibly coeval with the coeval with the Woodford. These include the Bakken
uplift of the Texas arch. To the west, the basin con- Formation in the Williston Basin, the New Albany
tinues into the El Paso area and southern New Mexico. Shale in the Illinois Basin, and the Antrim Shale
To the south, it was presumably open to the ocean, in the Michigan Basin, each in intracratonic basins.
where deep-marine sediment were deposited in the The Ohio Shale in the Appalachian Basin and the
Marathon and Ouachita basins. Chattanooga Shale in the Warrior Basin are both
The earliest record of To bosa Basin subsidence is foreland basins (Roen, 1984; Fairhurst, 2015, 2016).
the Middle Ordovician Simpson Group, a complex The West Texas Super Basin is a bit of a hybrid. The
of sandstone, shale, and some limestone (Figure 6). Tobosa Basin was much like the intracratonic Wil-
Individual formations within the group pinch out liston, Illinois, and Michigan Basins but on a passive
and onlap to the east, indicating basin-margin con- trailing margin open on its southern margin to the
ditions onto the Texas arch that separated the To- open ocean on North America’s southern passive
bosa from the Anadarko Basin deposition. The trailing margin. Perhaps, most similar to the Williston
Simpson Group contains the oldest known organic- Basin, which was open to the free-circulating ocean to
rich source rock intervals in the basin. the west.
Subsequent deposition within the To bosa Basin The Woodford in the West Texas Super Basin was
was dominantly carbonate, including the Montoya, separated from the southern Oklahoma Woodford by
Fusselman, and Silurian–Devonian formations. By the the Texas arch, although the members and individual
middle Silurian, a shelf margin was developed, sep- layers are correlated between these two separate ba-
arating a shallow-water carbonate platform to the sins. Another significant difference was that the passive
north from chert-rich basin sediments to the south. trailing margin in Oklahoma was open to the ocean to
During the Middle Devonian, a pronounced epi- the south along the failed southern Oklahoma aulac-
sode of regional uplift and arching affected southern ogen more than the enclosed To bosa Basin.
North America. A prominent unconformity affected The Mississippian limestone (Lower Mississip-
the basin, and erosion on the Texas arch left only small pian) overlying the Woodford Shale represents the
remnants of many units. last basin-wide deposition within the Tobosa Basin.
The erosion was followed by a Late Devonian The Mississippian carbonates are also part of the last
transgression that deposited the organic-rich Wood- widespread carbonate-producing epeiric sea of the
ford Shale in Oklahoma, Texas, and New Mexico. North American craton and into the marginal fore-
Figure 7 is an isochore map of the Woodford in the land basins (Dott and Batten, 1976). Subsequent
West Texas Super Basin. The Woodford extends tectonic activity in North America divides the conti-
over a larger area than the Simpson Group iso- nent, especially the southern and western margins, into
chore forming the more oval shape of the Tobosa more distinct basins with more varied tectonic and
Basin defined by Galley (1958) and most typically sedimentological development than the more uniform

1110 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 tectonic and sedimentological histories during the lower legged orogeny. Uplift boundaries are commonly
and middle Paleozoic (Fairhurst, 2015, 2016, 2018). faulted, with reverse and strike-slip components of
The Mississippian limestone (Kinderhookian– motion. Small but deep elevator basins (Broadhead,
Osagean) in the To bosa Basin is thickest on the north- 2004) also occur along regional fault trends. Uplift
ern platform, thinning into the central and southern and basin subsidence proceeded in tandem, with
parts of the basin (Fairhurst and Rogers, 2018). The variations in timing from place to place but generally
top of the Mississippian limestone makes for an between the latest Mississippian and the early Permian.
excellent regional mapping horizon, but the unit On the west side of the basin, an axis of uplift
has proven to be an insignificant producing reservoir forms the Diablo and Pedernal uplifts; internal struc-
or petroleum source rock system. Only five fields ture here may be complex in areas, but together they
exist that produced more than 1 million bbl of oil separate the deep Delaware Basin axis from the Or-
with just more than 15 million bbl of oil total ogrande basin in New Mexico and the Marfa basin in
in Yoakum (northern shelf), Dawson, and Borden westernmost Texas. The central basin axis is generally
Counties in the northern Midland Basin (Dutton high-standing within the basin and contains areas of
et al., 2005a). substantial uplift and erosion (Figure 4). The Delaware
Mississippian limestone isochore thins are caused Basin’s deep trough lies to the west, and the Val Verde
by erosion during Pennsylvanian and pre-Permian Basin lies to the south.
(basal Wolfcamp) unconformity. Even correcting for Complex faulting extends across the Delaware
the lost section caused by uplift, there is still evidence Basin and central basin axis and into the shallower
of the early development of the central basin axis Midland Basin. Within this system of faults, smaller-
(Fairhurst and Rogers, 2018). The Mississippian lime- scale uplifts and basins occur that form the main
stone and Barnett Shale appear to mark a transition structural traps for hydrocarbons in the basin. These
from the Tobosa structural and sedimentological basin field-scale (macroscale) structures include faulted
and coeval final stage of the North American craton anticlinal ridges, equant trapdoor uplifts with faulted
epeiric sea to the next phase of basin development. margins on two sides, narrow linear ridges, flower
structures, and high-relief ridges with overturned
margins, especially in the Delaware Basin (Ewing,
ARM Late Mississippian–Early Permian 2019; Fairhurst, 2015, 2021).
Influence on Basin Development These macroscale structures can be organized
into domains with similar features and geometry
During the Meramecian–Chesterian, a shelf margin (Figure 4). In the north, the Tatum ridges domain
separated a deeper, southern basin accumulating the consists of narrow faulted linear ridges in a struc-
organic-rich Barnett Shale from the northern car- turally depressed area (Tatum Basin). To the south at
bonate platform (Ruppel et al., 2020d). The change the north end of the megascale central basin uplifted
in the lower Barnett, high resistivity, high total or-
axis, a southeast-trending set of anticlinal ridges forms
ganic carbon (TOC), good mud-log shows, and mixed
the Hobbs transverse zone, passing southward into
silica and carbonate, to upper Barnett, lower-resistivity,
the south-southeast trending ridges of the Eunice-
lower TOC, poor mud-log shows, higher terrigenous
Andector ridges. These ridges have reverse faults on
shales, and lack of or low carbonate percentages may
the east and general westward dip, giving an east-
be a useful boundary marker from the transitional phase
vergent geometry that contrasts with the overall west-
to the active ARM–Marathon-Ouachita tectonism.
The Late Mississippian large-scale uplift, fault- side down pattern of the central basin axis (Figure 9A).
ing, and basin subsidence is part of the ARM orogeny Farther south, the zone passes into a southeast-trending
in southwestern North America (Figure 8). The ARM zone of equant structures and narrow ridges, the
is a series of basement-cored uplifts and deep basins Monahans transverse zone; its southern boundary is a
extending from Texas and Oklahoma northwestward major throughgoing fault with strike-slip motion that
through Colorado and farther northwest (Kluth, passes eastward into the left-lateral Big Lake fault zone.
1986; Dickerson, 2003). The West Texas Super Basin South of this fault is a large triangular block that
structures lie on the southern prong of this three- has been uplifted en masse, with only one internal

Fairhurst et al. 1111

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 6. (A) Isochore map of the Simpson Group (contour interval = 500 ft) modified from Fairhurst (2015). The axis and western
margin of the Simpson isochore of the To bosa Basin are similar to the axis of the current Delaware Basin. The eastern margin through
central Martin, southwestern Glasscock, and eastern Regan Counties includes only the western half of the current Midland Basin. In-
dividual beds display thinning onto the margins, and there are indications of erosion along these margins. (B) Middle Permian basin and
platforms (see Figure 1 for location) overlying the Simpson isochore map.

1112 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 6. Continued.

dividing fault, the Fort Stockton uplift and Sand Hills 9B). South of the uplift, the central basin axis is a
block. This uplift, with the Proterozoic subcropping narrow belt of faulted anticlines, the Puckett zone
beneath Permian units, is distinctive in the area. It extending south and passing beneath the Marathon
was thrust southwestward on a high-displacement fold–thrust belt. Within the Delaware Basin are many
thrust system over the southern subbasin, Round high-relief structural features; in particular, the Coya-
Mountain subbasin, of the Delaware Basin (Figure nosa zone contains overturned anticlinal features.

Fairhurst et al. 1113

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 7. Isochore map of the West Texas Super Basin, To bosa Basin Woodford (contour interval = 100 ft; modified from Fairhurst,
2015; Fairhurst and Rogers, 2018) overlain by Permian Basin tectonic features from Ruppel (2019a).

In the southeast, the southern Devils River uplift belt, which impinged on the continent during this time
was formed and thrust northward over the Val Verde (Wuellner et al., 1986; Fairhurst, 2015, 2016, 2018).
Basin during the Late Pennsylvanian and early Perm- The Ozona arch to the north may represent a
ian. The Val Verde Basin has been described as a forebulge to this basin, although it does not show
foredeep to the thin-skinned Marathon fold–thrust extensive erosion after the Middle Pennsylvanian.

1114 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 8. Location of the Ancestral Rocky Mountains and Permian Basin major features from Ewing (2016, 2019). Uplifted areas in
brown, deep basins are in blue; continental margin positions are shown. AR = Arkansas; AZ = Arizona; CBA = central basin axis; CCT =
central Colorado trough; CO = Colorado; Del = Delaware Basin; KS = Kansas; NE = Nebraska; NM = New Mexico; OK = Oklahoma; Unc-
SDC = Uncompaghre-San Luis-Sangre de Cristo uplift; UT = Utah; WY = Wyoming.

Significant fault systems pass through and con- from southern Oklahoma, overthrusts of the Anadarko
nect the structures. In the basin’s northern and Basin, and left-lateral strike-slip (Figure 8) extending
eastern extremities, two linear trends of en echelon into Colorado. It is noted that this direction of com-
faulting, uplift, and basin development were active pression is inconsistent with the generally northwest-
during the Early Pennsylvanian forming the Matador trending compression responsible for Marathon and
and Fort Chadbourne fault zones (Figure 4). West- Ouachita thrusting. It may be the result of ARM
northwest–trending faults are well documented in tectonism or antithetic motion to the north-northwest
the southern Midland Basin (Big Lake and Todd- compression of the Marathon-Ouachita tectonism.
Elkhorn faults) and pass into the Delaware Basin Sources for the northeast, north-northeast com-
(Monahans, Grisham, and Huapache faults). The two pressive stress may also be sought either in eastern
transverse zone domains are consistent with a com- Laurentia (Appalachian suturing) or to the southwest
ponent of strike-slip in the same direction. North- (interactions with proto-Pacific terranes on a mostly
south–trending faults are less abundant south of the buried margin in northwestern Mexico (Ye et al.,
Tatum Basin domain but may occur in various areas; 1996; Leary et al., 2017).
displacement is unknown but likely dextral. It is incorrect to refer to the West Texas Super
Overall, the mapped structures indicate a north- Basin as a foreland basin related to the Marathon-
east to north-northeast compressional stress (Ewing, Ouachita belt. The Marathon-Ouachita does gener-
2019), consistent with reverse fault trends and trends ate foreland basins, namely, the Arkoma, Fort Worth,
of strike-slip faults. Stress may have varied over some and possibly the Val Verde and southern Delaware
40 m.y. of deformation, but that variation is not Basins. But the remainder of Permian Basin structures
resolvable with confidence. A northeast, north- and the later Permian subsidence have no direct
northeast compressive stress is consistent with evidence connection to the Marathon-Ouachita thrust loading

Fairhurst et al. 1115

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 9. Crustal cross sections of the central basin axis from Ewing (2016, 2019). (A) northern west-east section from the Guadalupe
Mountains across the Malaga subbasin, the northern central basin axis, and the western Midland Basin; (B) southern southwest-northeast
section from the Davis Mountains across the Round Mountain subbasin, Fort Stockton uplift (FSU), and southern Midland Basin. A = away
on strike-slip faults; CO = Cambrian and Ordovician; COSD = Cambrian, Ordovician, Silurian, and Devonian; CRET. = Cretaceous; MISS. =
Mississippian; PENN. = Pennsylvanian; SD = Silurian and Devonian; T = toward strike-slip faults; Vp = P-wave velocity (km/s).

1116 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 other than potential movement along the lines of Africa, and South American plates forming Pangea
weakness formed during Cambrian rifting and the (Dott and Batten, 1976; King, 1977). The timing
Precambrian lines of weakness much like the south- of the north-to-south foreland basin development
ern Oklahoma aulacogen and megastructures. includes the Appalachian Basin (Devonian), the
Yang and Dorobek (1995) have nicely modeled Warrior Basin, Alabama to Mississippi, (Mississippian),
the section of Figure 9B as thrusting of the Fort the Arkoma Basin (Mississippian–Pennsylvanian), the
Stockton high over the deep Round Mountain sub- Fort Worth (Late Mississippian–Pennsylvanian), and
basin, with the Midland Basin as a back-thrust basin. the West Texas Basin, including its newly formed
However, the same model cannot be applied in the and segmented Val Verde and southern Delaware
northern central basin axis (Figure 9A). It is sug- and Midland Basins (Late Mississippian through early
gested that the east-verging macroscale structure versus Permian). The west Texas area has the youngest
the westward-verging megascale high-low relationship tectonic onset, latest basin formation, and youngest
indicates a detachment within the crust, which could sedimentary basin fill. The convergence formed deep
be related to the complex, layered basement of the basins filled with organic-rich mudstones and high
north part of the basin (Figure 9A). sediment load, siliciclastics, from adjacent rising
mountain belts. Sediment load was derived from the
craton and former deep-marine sediments (Marathon
Marathon-Ouachita Late and Ouachita facies) into the newly forming Val
Mississippian–Early Permian Influence Verde and southern Delaware and Midland Basins
on Basin Development (Fairhurst, 2016, 2018; Fairhurst and Rogers, 2018).
The convergence in west Texas caused by both
The Marathon-Ouachita orogenic event was active ARM (west-southwest to east-northeast) and plate
to the south. Crustal and basin down-warping caused convergence (south-southeast to north-northwest)
by convergent plate boundaries and high sediment caused uplift of the central basin axis that divided
load followed by thrusting occurred within the Val the former Tobosa Basin into the Val Verde, Dela-
Verde Basin into the southern newly developing ware, and Midland Basins (Figures 1, 4, 8). The
Delaware and Midland Basins. The influence of the central basin axis may have been uplifted by re-
Marathon-Ouachita orogeny decreases south to north, activation of the Pecos and Hobbs mafic intrusive
with the most significant impact on the Val Verde complexes. The primary, right-lateral fault move-
Basin, central basin axis, southern Delaware Basin, ment accounts for most movement along the central
and southern Midland Basin in degreasing significance. basin axis western margin into the Delaware Basin.
The convergence likely reactivated the south- Antithetic left-lateral strike-slip faulting and coun-
southeastern–trending Delaware aulacogen, To- terclockwise rotation of major blocks within the
bosa Basin faults, and lineaments, resulting in central basin axis have been documented. Along
primary right-lateral wrench faulting along both both the primary and antithetic strike-slip systems,
western and eastern margins of the central basin axis transpressional, pop-up structures form many con-
into the proximal Delaware and Midland Basins ventional producing fields along the central basin
margins similar to the slightly earlier Carboniferous axis western margin. Transtensional, pull-apart sub-
tectonic development of the Anadarko Basin along basins and structures along the eastern and western
the southern Oklahoma aulacogen, the lower Paleo- margin of the central basin axis form sedimentary
zoic passive trailing margin in Oklahoma. depressions filled with Barnett through Pennsylva-
The same tectonic setting (continental–continental nian sediment that produce hydrocarbons and are
plate collision) that generated the crustal loading, current exploration targets (Fairhurst, 2015, 2016,
deep foreland basins, and subsequent mountain 2018; Party, 2020).
building then thrusting of older deep-basin facies The central basin axis active faulting and con-
(allochthonous facies and thrust sheets) over foreland tinued uplift resulted in the deposition of the Barnett,
faces (autochthonous facies and subthrust blocks) in Pennsylvanian, to early Permian strata. Motion on
west Texas is a progressive north-to-south zippering faults and development of detrital sediments in var-
(mergence) of the North American plate to Europe, ious parts of the basin indicate Late Mississippian and

Fairhurst et al. 1117

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Early Pennsylvanian transition into more active struc- movement forming the positive structural hydrocar-
tural development during the Late Pennsylvanian– bon traps and down-throw blocks (subbasins) within
early Permian (middle Wolfcampian). The largest the larger basins and central basin axis. The defor-
structures in the basin appear to be Late Pennsylva- mation and subsidence are most pronounced in the
nian and early Permian in age, especially along the southern central basin axis (e.g., the Fort Stockton
central basin axis. Seismic lines in many areas show a block), southern Delaware Basin, and Midland Basin.
sharp cessation of high-relief folding and faulting Continued subsidence through the Permian (middle
(Late Pennsylvanian) and tilting at a zone in the Wolfcampian–Ochoan) is not part of this event. That
middle Wolfcampian (Calle et al., 2019; Fairhurst, later subsidence must be attributed to post-ARM, later
2021). Some uplift and faulting may occur in younger Rocky Mountain, or other deformation influences de-
strata from continued subsidence of the basin (middle fined by the previous discussion and subsequent section.
and late Permian). Figure 10 illustrates some of these relationships
In the West Texas Super Basin, this significant in the northwestern central basin axis. Figure 10A is
tectonic event uplifted the mafic Pecos-Hobbs mafic an isochore map from the base of the Permian
complex (Figure 5), which may have been the root (Wolfcampian) to the top of the Mississippian lime-
for an earlier subsiding Tobosa Basin. Now forming stone (base of the orange interval to top of blue interval,
the central basin axis, the axis separated the Tobosa cross section in Figure 10B). All wells, producing (oil
Basin into the Delaware Basin, central basin axis, and [green] and gas [red]), water injector (blue), and dry
the Midland Basin. Previously, the Tobosa Basin was holes (black), are shown on the isochore map
centered under the Delaware Basin with the later (Figure 10A). The right-lateral wrench-fault move-
developing central basin axis on the deeper part of ment of the western margin of the central basin axis
the eastern flank and the Midland Basin still farther and the Delaware Basin can be inferred from the
east over the shallower part of the eastern flank of the location and geometries apparent in the isochore
Tobosa Basin. The Val Verde Basin to the south is map. Parts of the central basin axis defined by the
likely the only fully developed foreland basin of dark to light gray, low, isochore values illustrate the
the tectonic event with its axis roughly parallel to central basin axis westward extension. Right-lateral
the Marathon Mountains and normal to subnormal to compression of these westward extensions caused
the orogenic event stress. The Mississippian, Pennsylvanian, transpressional force on the central basin axis, re-
and early Permian (early Wolfcampian) subsidence sulting in pop-up structure along high-angle reverse
caused by this event in the Delaware and Midland faults that are major producing fields. Examples are
Basins and central basin axis uplift are parallel (not Keystone field in northcentral Winkler County just
normal) to the orogenic stress similar to the Ardmore south of the southern corner of New Mexico and
and Anadarko Basins and associated Arbuckle and Dollarhide field just east of the New Mexico line
Wichita Mountains in Oklahoma (Perry, 1989) in southwesternmost Andrews County. In between,
along former (lower Paleozoic: Delaware aulacogen, where the central basin axis extends eastward, caused
Tobosa Basin, and basement faults, fractures, or transtensional force and down-dropped basins. With
basement variations) lines of weakness. the right-lateral movement, a void is created, forming
The direction of the Marathon system thrusting the down-dropped subbasins. The rhombohedral
caused significant strike-slip movement within the West shape of faulting and extension along high-angle
Texas Super Basin. The primary motion (north- normal faults are clearly identified on 3-D seismic
northwest) of that movement appears to be right-lateral time slices. The extension caused the development of
with left-lateral antithetical movement (west-northwest) these subbasins.
between major blocks of the central basin axis forming In the northern of the two subbasins shown,
counterclockwise rotation of the Fort Stockton and other named the Flying Dove subbasin (Figure 10B; Fairhurst,
major central basin axis blocks (Yang and Dorobek, 2015), the Barnett thins onto the basin margin but has
1995; Tai and Dorobek, 2000) and into the basins also been eroded on the basin shoulders by a synde-
(e.g., Big Lake fault, Ewing, 2019). The wrench-fault positional and the pre-Permian unconformity. The
movement accounts for miles of lateral displacement Barnett did not have continuous, uniform thinning
and up to several thousands to 10,000 ft of vertical onto the basin margin. It appears the lower Barnett

1118 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 10. Geologic development of the northern central basin axis, Delaware and Midland Basins during the Late Mississippian
through early Wolfcampian from Fairhurst (2015). (A) Isochore map from the base of Permian (Wolfcampian) to top of the Mississippian
limestone; contour interval = 100 ft; dark gray to white is 0–500 ft; blue is 500–1000 ft; green is 1000–1500 ft; yellow-green to yellow
is 1500–2000 ft; yellow to orange is 2000–2500 ft; and red is more than 2500 ft. (B) North-south structural cross section AA9. L = Lower;
Ms Lm = Mississippian limestone; U = Upper.

Fairhurst et al. 1119

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 was deposited before significant structural development Both ARM and Marathon-Ouachita tectonic
with most of the thinning and erosion in the upper events caused the deep-basin subsidence and uplift
Barnett, which is missing over the subbasin shoulders. of the central basin axis separating the West Texas
The lower Barnett in this area was deposited as the last Basin into the component parts of the Delaware,
stage of the Tobosa Basin (predeformation). The upper Midland, Val Verde, and other subbasins during the
Barnett was deposited syndepositionally or immedi- Late Mississippian through early Permian (middle
ately after tectonic-structural development and sub- Wolfcampian). Individual elements are attributable
sidence of the subbasin. to one or a combination of these tectonic-orogenic
Many of the wells in this cross section and the events (e.g., Coyanosa subbasin development). De-
subbasins have hydrocarbon shows trapped by the formational styles associated with each of these
basal Wolfcamp, the Strawn, and deeper Woodford. significant coeval, overlapping events have been
The Hogg subbasin (southern of the two subbasins, provided. Further definition and revision at specific
Figure 10A, B) has produced 32.8 million bbl of oil localities will be more location specific and detailed
and 72.6 BCF of gas through June 2014 from 145 and will be defined by future work and publications.
wells and 18 different Pennsylvanian reservoirs, mostly
Strawn (Fairhurst, 2015). Apache was the most active
operator drilling 13 horizontal wells during 2011– Permian Basin: Permian Intracratonic
2014, with others planned at that time. Subeconomic Subsidence Outlasting Deformation
production has been found in the Strawn, Barnett, and
Woodford in the Flying Dove subbasin (northern of A major episode of regional subsidence occurs in the
the two subbasins). Other operators are targeting late Paleozoic, overlapping and outlasting ARM and
similar plays along subbasins, structural lows, or pinch- Marathon-Ouachita deformation. Super-Wolfcampian
out of Barnett through Upper Pennsylvanian on the rocks exceed 2400 m (8000 ft) in thickness near the
Midland Basin and central basin axis boundary on the corner of New Mexico and exceed 3000 m (10,000
eastern side of the central basin axis (Fairhurst, 2015; ft) in the Delaware Basin (Figure 11A). Some of this
Party, 2020). thickening reflects Wolfcampian bathymetry (McKee
The lower and upper Morrow, a lowstand de- and Oriel, 1967). Preserved Permian deposits form a
posit, lap onto the Barnett, filling only the lower part vertical spoon-shaped geometry, gently tapering to
of the Flying Dove subbasin and thinning onto the the north and east, more sharply to the west and
subbasin margins in the Hogg subbasin (Fairhurst, southwest. However, the basin’s eastern, southern, and
2015). The Atoka, Strawn, and Cisco–Canyon de- southwestern margins were modified after Permian
posits show no thinning onto the basin margins in the deposition.
Flying Dove subbasin and southern Hogg subbasin Typical 1-D sediment accumulation curves are
but thin on the northern margin of these subbasins. shown in Figure 11B. Near the basin center at Toyah
It is interpreted that these lowstand units were de- Lake field near Pecos, subsidence began in the Penn-
posited only within the subbasin (onlap) and out into sylvanian, accelerated in the Wolfcampian, and con-
the Delaware Basin. In these areas, the Pennsylvanian tinued at a lower but steady rate until the close of
was deposited after the significant structural devel- the Permian. Deep-water conditions persisted through
opment during the passive subsidence of the subba- most of this time at this location, leading to some un-
sins. Major structural development during the certainty in detail. On the northeast flank of the basin at
Pennsylvanian through the early Wolfcampian is Kelly Snyder field (Figure 11B), steady subsidence is
documented farther to the south. recorded from the Middle Pennsylvanian through
The Coyanosa subbasin to the south and Waha Guadalupian. This location was near sea level nearly all
structure (not mapped here) formed along a wrench of this time. Ewing (2019) presents a sediment accu-
fault, flower structure likely to have similar tectonic- mulation (subsidence) analysis across the basin, show-
structural origins (strike-slip faulting) to the positive ing significant tectonic subsidence in the middle and
structural features and subbasins illustrated in Figure late Permian over most of the basin.
10. These structures were actively developing through Subsidence is inferred to begin in the Early
the middle Wolfcampian (early Permian). or Middle Pennsylvanian, therefore overlapping the

1120 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 11. Permian sediment accumulation: (A) map showing thickness of super-Wolfcampian Permian strata from Ewing (2019, used with
permission from AAPG) after McKee and Oriel (1967). Contours outline the area of enhanced post-ARM subsidence, as modified by post-
Paleozoic uplifts. (B) Lower Paleozoic–Permian sediment accumulation curves for two locations in the Permian Basin: Toyah Lake field (left)
near the Delaware axis and Kelly-Snyder field (right) to the northeast. Curves are corrected for compaction, and water depths are estimated
from published sections. CH = Mexican state of Chihuahua; Co. = County; CO = Colorado; COA = Mexican state of Cohuila; KS = Kansas; LG
and Lo. Guad = lower Guadalupian; LO. PENN. = Lower Pennsylvanian; MTNS = Mountains; NM = New Mexico; O. = Ochoan; OK =
Oklahoma; PZ = Paleozoic; TX = Texas; UG = upper Guadalupian; UP. PENN. = Upper Pennsylvanian.

Fairhurst et al. 1121

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 development of the ARM, Marathon-Ouachita basins, extensive bowl of subsidence by crustal flexure. This
and uplifts from these orogenic events. Evidence for subsidence is most similar to the early to mid-Paleozoic
the general basin-wide subsidence is the general lack of Tobosa Basin, not the active tectonism from the Late
erosion of the uplifted blocks. Most of the central basin Mississippian to middle Wolfcampian.
axis does not expose Precambrian rocks; it primarily
forms a pedestal for deposition of Pennsylvanian,
Wolfcampian, Leonardian, and Guadalupian car- Post-Permian Modifications of the Basin
bonate platforms. Subsidence continued past the and Its Margins
middle Wolfcampian cessation of large-scale tec-
tonic activity and persisted into the late Paleozoic. The West Texas Super Basin was modified around
A regional carbonate platform in the Middle its margins during Mesozoic and Cenozoic tectonic
Pennsylvanian is drowned in the Late Pennsylvanian, events; however, the central part of the basin was
with the formation of shallow-water carbonate affected only slightly by such events (Brown, 2019;
platforms and pinnacles over the central basin axis, Ewing, 2019). In the early and middle Mesozoic,
the gentle Garza arch in the northern Midland Basin, uplift and tilting affected the eastern, southern, and
and on the basin margins. This configuration of deep southwestern margins of the basin, as shown on the
basins and platforms persists through the Permian. Cretaceous subcrop map (Figure 12A). In the basin
The Midland Basin gradually shallows in the Gua- center and north, Permian sediments were overlain
dalupian. The entire West Texas Super Basin is filled by Upper Triassic alluvial and lacustrine sediments of
and sealed with evaporates in the late Permian the Dockum Group, which extends northwest into
(Ochoan) once the connection to the world ocean is the Chinle and Moenkopi Formations of New Mexico
lost. The (Wolfcampian, Leonardian, and Guadalupian) and the Colorado Plateau. To the east, a gentle
deep-water basins, connected by shallower channels to beveling of Paleozoic rocks is evident on regional
the world ocean, developed persistent anoxia, which geological maps, culminating in the Llano arch. This
allowed for the accumulation of organic-rich shales in uplift is likely a rift shoulder coeval with the Late
the Wolfcamp and other Permian Basin strata. Triassic Eagle Mills Formation deposition in rift basins
This Permian (late Wolfcampian–Ochoan) sub- in east Texas that mark the early opening of the Gulf
sidence phase, first separately identified by Horak of Mexico Basin. To the southwest, a similar regional
(1985), is chiefly responsible for the basin’s profound pattern of beveling rises toward the Hueco arch. This
hydrocarbon productivity. It both allowed anoxic arch is likely the rift shoulder to the Chihuahua
basinal environments to persist for long periods and trough, a part of the Upper Jurassic border rift
provided sufficient sediment cover (augmented in system. To the south, there is a distinctive high-angle
the Mesozoic) to mature the source rocks into the oil homocline exposed in the Glass Mountains at the
window. north side of the Marathon window. Here Paleozoic
The subsidence covered a large area and has a strata dip up to 6° more steeply than overlying
geometry and scale similar to other North American Cretaceous rocks. This Glass Mountains homocline
intracratonic basins. It is centered on the Tobosa extends eastward into the subsurface, causing Permian
basin axis and western margin of the central basin strata to be eroded beneath Cretaceous rocks and
axis, which lies above the Delaware aulocogen axis, raising maturity levels in the Val Verde Basin. This
To bosa Basin axis, and western margin of the 1100– homocline may be related to Late Triassic and Jurassic
1200 Ma mafic intrusive axis, the Pecos intrusive rifting to the east or Jurassic rifting to the southwest.
complex, and correlatives to the northwest. Similar During the late Early Cretaceous (Albian), the
relationships occur in the Michigan Basin, which lies entire area was flooded by the sea and developed
on a Precambrian rift axis filled by the Keweenawan shallow-water carbonate platforms (Edwards Group)
Supergroup. It is possible that post-ARM and and muddy off-shelf basins. Upper Cretaceous strata
Marathon-Ouachita convergence, the Pecos complex (mainly shale and chalk) were deposited over the
mafic root was forced downward into the mantle. Such area. These are preserved in the Big Bend arch of
a downwelling could create a downward force or “pull” Texas, the Raton Basin to the north in New Mexico,
at the basin center, which may have formed an and the Texas Gulf Coast. In west Texas, these units

1122 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 12. Post-Paleozoic modifications to the Permian Basin were adapted from Ewing (2016, 2019). (A) Cretaceous subcrop map,
from Ewing (2019, used with permission from AAPG) projected where Cretaceous strata have been eroded. (B) Post-Cretaceous modifications;
structure map, top Lower Cretaceous (TLK), Laramide (underlined), and basin and range structural elements. CH and CHI = Mexican state of
Chihuahua; COA = Mexican state of Cohuila; FZ = fault zone; GMH = Glass Mountains homocline; NM = New Mexico; OK = Oklahoma;
PC = Precambrian; PENN. = Pennsylvanian; TU = Tascotal uplift; TX = Texas.

Fairhurst et al. 1123

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 are mostly eroded during the Neogene. The Creta- The elements of the West Texas Super Basin
ceous burial was significant in extending the area of encompass the first four of the seven criteria of a super
source rock maturity in the Midland Basin. basin defined in the Introduction section: (1) one or
From the latest Cretaceous into the Paleogene, more petroleum systems, some linked to other regions
compression along North America’s western margin or continents; (2) geologic architecture and timing of
created a diverse assemblage of structures during the petroleum systems for generation, migration, and en-
Laramide orogeny (Ewing, 2016). In west Texas, trapment of reserves; (3) production of 5 billion BOE
major features include an uplifted area from Mara- and having 5 billion BOE remaining recoverable re-
thon to the southeast. The Santiago thrust fault serves; and (4) many pays and plays. Having defined the
system bounds the southwest. The fold belts to the relationship between the tectonic and basic sedimen-
west (Chihuahua) and southeast (Del Rio) and strike- tological history of this prototypical super basin, the
slip faults to the northwest in southcentral New following highlights the petroleum systems elements.
Mexico (Border Buckles) and south Texas (Carta For an understanding of the West Texas Super
Valley fault zone) document activity during this time Basin petroleum systems, it is essential to understand
(Figure 12A). Reactivation within the basin proper is the basin from the basement and in the context of
minor, although locally reported (Winfree, 1994). the tectonic and sedimentological history provided.
Beginning in the Oligocene, uplift and extension In this case, the basement is a petroleum economic
began to replace the earlier compressional stresses. basement and the nonsedimentary, igneous, and
Volcanism and igneous intrusion were widespread in metamorphic basement. Because this prototypical
trans-Pecos, Texas. Basin and range normal faulting super basin is such a rich petroleum resource, every
and limited basaltic volcanism occurred in that area, element, dimension (four dimensions), volume of sed-
extending eastward to the Santiago fault zone (re- imentary rock (preserved and missing), and synthesized
activated in a normal sense) and the west end of the geologic principles are significant in reconstructing an
Guadalupe Mountains (Salt Basin graben). On the understanding of the petroleum systems.
shoulder of active rifting, the crust was uplifted sev- The first criterion for super basins includes linkage
eral thousand feet (1–1.5 km) and tilted the basin to to other regions or continents. During the Paleozoic,
the east. This is part of the Alvarado ridge of Eaton three major worldwide source rock petroleum sys-
(1987). This tilting is most evident in the central Del- tems have been recognized. They are Silurian, Upper
aware Basin, where the Permian shelf margin, slope, and Devonian, and Pennsylvanian–upper Permian (Klemme
basin units are uplifted and tilted to form the Guada- and Ulmishek, 1991). Grunau (1983) provided an
lupe and Delaware Mountains on the eastern flank of earlier summary of those sources with the only slight
the Salt Basin graben. This tilting has uplifted maturity variation by Klemme and Ulmishek (1991). These
levels in the western and central Delaware Basin. works included source rocks for only conventional
giant reservoirs (Figure 13). Updated figures that
include unconventional resources will likely confirm
PETROLEUM SYSTEMS greater contribution from the three major Paleozoic
source periods to the total contribution of worldwide
Petroleum systems follow organic material from or- production now that the industry is producing hy-
igin, deposition, preservation, burial, maturation, ex- drocarbons directly from these source rocks. Within
pulsion, migration, entrapment, confinement (seals), the West Texas Super Basin, the second two of the
and production (reservoir quality and technology). three global Paleozoic source rock petroleum systems
These include the interrelationships of these elements as are most significant. Other Paleozoic source rock
an associated or related set. These sets are sometimes petroleum systems occur and are discussed.
confined within the basin to specific geologic units
or geographic areas, especially if there is a single pe- Lower Paleozoic Petroleum Systems
troleum source. In basins like the West Texas Super
Basin with multiple world-class petroleum source Upper Cambrian siliciclastics are only present in the
rocks and locally important secondary source rocks, southeastern part of the basin. These siliciclastics grade
these petroleum systems commonly overlap. up into cherty carbonates of the lower Ellenburger,

1124 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 (A) Ellenburger is only productive in the upper units
where overlain by Simpson Group source rocks
(Galley, 1958) or, in some isolated cases, where the
Simpson is not present and the Ellenburger is overlain
by Woodford or Pennsylvanian shale source rocks,
primarily on the eastern shelf of the Midland Basin
north of the southern boundary of the Abilene gravity
minimum.

Ordovician, Simpson-Sourced Petroleum System

The Simpson Group is the transgressive unit for the
Tippecanoe Supersequence, a second-order sequence
(Sloss, 1963). It is divided into five formations: Joins,
Oil Creek, McLish, Tulip Creek, and Bromide, from
oldest to youngest (Figure 14). Connell, Waddell, and
McKee are three sandstone members at the base of
the Oil Creek, McLish, and Tulip Creek Formations,
respectively, which are transgressive marine units at
the base of each of these formations likely reworking
eolian sandstones and form the base of third-order
cycles (Jones, 2005). These sandstones are productive,
mostly where trapped stratigraphically along trunca-
tions and overlain by younger shales. Isolated sandstone
lenses appear to be more productive than regional
sandstone units (Wright, 1965). The middle and upper
parts of these (Oil Creek, McLish, and Tulip Creek)
formations, lowest Joins Formation, and upper Bromide
Formations are siliceous carbonates with interbedded
green and organic-rich darker shales.
Although Ordovician source rocks only account
for 1% or less of the petroleum source rocks world-
wide (Grunau, 1983; Klemme and Ulmishek, 1991),
the Simpson, Middle Ordovician petroleum system,
Figure 13. (A) Stratigraphic distribution of world’s conventional oil which sourced the Simpson sandstone (6% of the
and (B) gas by source rock percent from Sorkhabi (2009); sources: system production) and Ellenburger carbonate res-
Grunau (1983) and Klemme and Ulmishek (1991). Cam. = Cambrian; ervoirs (94% of the system production), accounts for
Carbon = Carboniferous; Cenz. = Cenozoic; Cret. = Cretaceous; Dev. = 6% of the total basin conventional oil production
Devonian; Jur. = Jurassic; L.–M. = Lower–Middle; Ord. = Ordovician; (1.754 billion bbl of oil of the 28.9 billion bbl of oil)
Perm. = Permian; Sil. = Silurian; Tr. = Triassic; U. = Upper. through 2000 (Dutton et al., 2005a). The Ordovi-
cian source rocks are estimated to account for 5.7%
becoming less siliceous and more carbonate rich as the of conventional reservoir oil reserves for the basin
Ellenburger carbonate ramp drowned sediment sources (1.782 of the 31.2 billion bbl of oil) to date (2020).
north and west. Evidence exists of Early Ordovician The high volumes of gas production from this pe-
Ellenburger thickening into the To bosa Basin, which troleum system, primarily in the Delaware Basin, are
became more pronounced during the Simpson Group not included in these figures.
(Middle Ordovician) deposition (Figure 6). “The oil-prone relationship between total organic
Little evidence exists of enough organic carbon carbon (TOC) and total hydrocarbons in Simpson
in the Ellenburger for it to be self-sourced. The Group shales in both west Texas and Oklahoma,

Fairhurst et al. 1125

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 14. West Texas (Permian) Super Basin Ordovician stratigraphic column from Jones (2005, courtesy of the Bureau of Economic
Geology). North American stages, conodonts, and time scale originally from Sloss (1963, 1988); Derby et al. (1991); Ross and Ross (1992);
Goldman et al. (1995); Pope (2004); Webby et al. (2004); Young et al. (2005). Gp. = Group; Lland. = Llandovery; N. Am. Ser. = North
American Series; SIL = Silurian; Tipp. = Tippecanoe.

compared to the lack of such a relationship in Lack of Silurian–Lower Devonian Source

Ellenburger samples, lends additional support to the Rocks
idea that Simpson Group shale sourced Ordovician
reservoirs (Katz et al., 1994)” (Jones, 2005, p. 22). The first significant worldwide petroleum source
With most of the hydrocarbons in Ellenburger system is the Silurian, contributing approximately
reservoirs sourced by the Simpson Group, over- 9% of all generated hydrocarbon worldwide (Grunau,
pressure in the source rocks had to be high enough 1983; Klemme and Ulmishek, 1991). The Upper
to overcome buoyancy pressure to migrate down- Ordovician–lower Silurian Fusselman Formation and
ward (Echegu, 2013). Greater overpressure is not middle Silurian–Lower Devonian Wristen Group rep-
uncommon during hydrocarbon source rock mat- resent almost continuous sedimentation in the West
uration and certainly not unusual in the West Texas Texas Super Basin during this interval. However, de-
Super Basin. positional conditions were too shallow in the Tobosa

1126 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Basin to accommodate organic material preservation States, Upper Devonian–Lower Mississippian is dom-
relative to the age-equivalent source rocks associated inated by organic-rich, dark mudstones.
with the significant reserves found in North Africa and Comer (1991, 2005, 2008) first recognized the
Arabia. The Fusselman carbonates are shallow, clear- correlations of the west Texas and Oklahoma Wood-
water platform facies that comprise very good reservoir ford and differences, including the increased clay in
facies (Ruppel, 2019b). The overlying Wristen Group the Texas Woodford compared to similar units in
has more diverse assemblages. The northern part is a Oklahoma. Ruppel et al. (2020c) more clearly de-
shallow-water platform and shelf margin with good fined the shallower platform as more detritally
reservoir quality. The southern region is “character- influenced, oxygenated environments and a separate,
ized by fine-grained, [slightly] deeper water carbon- more-distal, depositional system dominated by set-
ate mudstones” (Ruppel, 2020a, p. 29). Throughout tling of in situ sponge spiculites and radiolarians in a
the Silurian, it appears that the relatively shallow, deeper-water, anoxic environment. This deeper-water,
clear-water environment and slightly deeper, below anoxic environment and Woodford petroleum system
but near-wave base facies were open to ocean circu- are associated with the worldwide transgressive, anoxic
lation and not ideal environments for deposition or event creating the excellent source rock within this
preservation of organic material. These are not source petroleum system.
rocks. The 1.2 billion bbl of oil produced in these Like the Simpson petroleum system beneath
formations through the end of 2000 represents just it, the Woodford Shale sourced the two reservoir
more than 4% of the total conventional oil production systems, the Upper Ordovician to lower Silurian
in the basin (Dutton et al., 2005a). Fusselman Formation and middle Silurian to Lower
The Lower Devonian Thirty-one Formation is a Devonian Wristen beneath it, accounting for 7.4% of
micro- to crypto-crystalline deep-basinal chert in the the West Texas Super Basin conventional reservoir
southern basin to slightly coarser chert, with mixed production (Dutton et al., 2005a). Again, the source
deep-water and debris-flow facies in the central basin rocks overpressure had to be higher than the un-
and with cherty carbonates in the upper parts of the derlying reservoirs to overcome buoyancy pressure to
formation and northern parts of the basin (Ruppel create this downward migration.
et al., 2020b). Continuous porous chert in the center The Woodford remains more highly over-
of the basin and some more isolated porosity lenses pressured than the units immediately above and
in the northern part of the basin in both chert and below. The higher overpressure is typically highly
carbonate facies, especially on structure, have pro- correlated to better unconventional resource reser-
vided adequate conventional reservoir quality that voir production (Ikonnikova et al., 2019) and an
produces from both vertical and horizontal wells. attractive element for the Woodford in Oklahoma
These reservoirs have produced 896 million bbl of oil and the West Texas Super Basin. The higher detrital
through the end of 2000, approximately 3% of the component in Texas degrades the Texas Woodford
basin conventional reservoir production (Dutton et al., potential for consideration. The increased clay con-
2005a). tent increases the risk for drilling and completion
fluid incompatibility. Clay also reduces Woodford’s
brittleness (Comer, 1991, 2005, 2008; Fairhurst,
Upper Devonian–Lower Mississippian, 2015, 2016). However, there are lower detrital
Woodford-Sourced Petroleum System component, more distal deep water, anoxic source
rock, and potentially unconventional resource poten-
The Woodford Shale was deposited during the tial that remain unlocked. These likely will be defined
second of the significant worldwide source rock as new exploration targets in the West Texas Super
depositional and preservation phases from Late De- Basin as exploration geologists define and reduce these
vonian to Early Mississippian. In the West Texas Super risk factors associated with other positive, unconven-
Basin, the Woodford can be correlated unit for unit and tional resource reservoir parameters.
commonly bed for bed with the Oklahoma Woodford Another difference between the Woodford pe-
(Figure 15), the dominant source rock throughout troleum system and the petroleum systems above it
the midcontinent. Onshore in the continental United with the Simpson petroleum system below is the

Fairhurst et al. 1127

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 15. Log cross sections of the Woodford were modified from Comer (1991, 2005). (A) Comparison of the West Texas
Super Basin and Anadarko Super Basin Woodford members and individual units. (B) Woodford west-east stratigraphic cross section
in the West Texas Super Basin. The Woodford is thickest in the Tobosa Basin center, now deep Delaware Basin in Winkler County
(Co.), and thins to the east with erosion on the central basin axis. Fm. = Formation; GR = gamma-ray log; N = neutron density log;
SON = sonic log; SP = spontaneous potential log.

mixing of the Woodford and upper petroleum sys- Paleozoic. Hydrocarbon generation and migration do
tems into younger reservoirs on the central basin axis not occur until the late Permian to Mesozoic after the
and northern and eastern shelves of the West Texas formation of the conventional reservoir traps. Good
Super Basin. It is difficult to quantify the contribu- reservoir quality, excellent seals, trap formation prior
tion of each source within mixed source reservoirs; to oil generation, and migration provides the elements
however, one attempt by Echegu (2013) estimates for identifying and exploiting these petroleum re-
that the Woodford expelled 7.9% of total hydro- sources, both conventional and unconventional.
carbon generated in the basin.
The high pressure of the Simpson Group and
Woodford Shale and fine-grained, tight (low porosity Transition from the Tobosa Basin to
and permeability) nature of the Simpson, the Wood- Permian Basin Petroleum Systems
ford, and the Mississippian limestone including mul-
tiple intraformational shales and mudstones within The reservoirs and source rocks of the To bosa Basin
the reservoir formations provide excellent seals for petroleum systems were deposited over 120 m.y.
these systems. Trap formation occurs during the late (470–350 Ma). Including mixing into younger

1128 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 productive reservoirs, the Woodford petroleum Pennsylvanian as a significant basin-wide petroleum
system may impact petroleum systems elements de- source rock system.
posited over 210 m.y., including the Ochoan basin-
wide evaporitic seals. The less-active Tobosa Basin
sedimentation terminated during the transition into Permian-Sourced Petroleum Systems
more active West Texas Super Basin tectonic events.
This transition and the petroleum system depos- Wolfcamp-Sourced Petroleum System
ited during the transition is the Barnett (Middle– Tectonic development and basin subsidence con-
Late Mississippian). The tectonic shift may have tinued into the middle Wolfcampian (Wolfcamp C;
initiated slightly earlier in the Mississippian with the Figure 16), especially in the southern part of the
emergence of the central basin axis recognized in basins. By late Wolfcampian, faulting subsided quickly,
Mississippian limestone isochore thinning over this although the significant basin subsidence continued
feature. creating very pronounced platforms, deep basins, and
Klemme and Ulmishek (1991) indicate that only rapid, or short-distance, transition between the two.
0.4% of the world’s hydrocarbon resources produced The northwestern, northern, eastern, and southern
have Visean and Serpukhovian (Middle and Upper margins of the basin were blocked from open-ocean
Mississippian) source rocks. The West Texas Super circulation. The only open-ocean access was likely to
Basin Barnett (Meramecian and Chesterian of North the west-southwest, Hovey channel, or unknown
America coeval to the Visean and Serpukhovian in- opening, now hidden by Oligocene Diablo platform
ternationally) is equivalent to the Fort Worth Barnett development. Some limited opening continued dur-
and Caney Shales of the midcontinent. The Barnett is ing the Leonardian and Guadalupian but was cut off
an excellent source rock and has seen activity as an during the Ochoan. As a result, the evaporitic facies
unconventional resource reservoir in both the Mid- north and northeast of the West Texas Super Basin
land and Delaware Basins (Fairhurst, 2015; Party, prograded into this now isolated basin. Basin subsi-
2020). Unlike the first two To bosa source rocks sys- dence continued resulting in more than 2000 ft of
tems (Simpson Group and Woodford), the majority evaporites being deposited in the Midland Basin,
of Barnett source rock migration has been upward 1000 ft over the central basin axis, and 5000 ft in the
into younger reservoirs and from the deep basin Delaware Basin.
into the central basin platform and shelf areas sur- The industry developed the term Wolfcamp D
rounding the basin. Echegu (2013) defines the for the Cline play on the eastern shelf into the
Devonian–Mississippian, Woodford, and Barnett sour- Midland Basin. The terminology later carried over
ces as one petroleum group. He calculates that the group into the Delaware Basin. The Wolfcamp D is actually
has sourced more reserves in the West Texas Super the Cisco and Canyon Group, Upper Pennsylvanian.
Basin than any other source rock petroleum system. It has been a successful unconventional resource play
During the Pennsylvanian, tectonic stress in isolated areas of both basins but is not a significant
continued to develop the major basin features rec- play, comprising only 2% (259) of total horizontal
ognized as the Permian Basin (Figure 1). The Wolfcamp wells drilled (F. R. Male, 2020, personal
secondary structures, the general scale of up to 10 mi communication).
in length and 5 mi wide, the scale of the large field During the early Wolfcampian (Wolfcamp C),
structures in the basin, and subsidence within both basin subsidence continued being thickest in the
major basins were also actively developing. The scale southern Delaware Basin, likely representing the last
of individual features is most influenced by the depth stages of Marathon orogenic activity and active basin
into the basement; those structures are seeded (Ew- subsidence from this event. In the southern Dela-
ing, 2019). The Pennsylvanian section has sufficient ware and Midland Basins, siliciclastic sandstones de-
organic material and adequate thickness to be con- rived from the western (perhaps southern) basin
sidered a separate resource. Locally in the Flying Dove margin were an exploration target during 2000–2010.
and Hogg subbasins and other areas, the Pennsylvanian This lowstand systems tract has low hydrocarbon
may be the dominant source rock. However, available saturation, mostly gas with high water cuts in the
studies do not support the consideration of the southern Delaware Basin. Rapid deposition of the

Fairhurst et al. 1129

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 16. Stratigraphic and operational names of the Wolfcamp interval from Fu et al. (2020). The O.L. Greer 2 well is in northern
Reeves County, Texas. Operational names are from Pioneer Natural Resources (2013). Substage and fusulinid zones are from Wahlman and
Tasker (2014, after Ross, 1963 and Wilde, 1990). Radiometric ages (in Ma) are from Henderson et al. (2012). The Wolfcamp B in the
Delaware Basin is a similar thickness to the B in the Midland Basin. The Wolfcamp C thicknesses vary considerably by locality. The Wolfcamp
A is 50% thicker in the Delaware Basin. D. = Desmoinesian; Fm = Formation; GR = gamma-ray in API units; M. = Moscovian; MWU =
middle Wolfcampian unconformity; NA = North American; Re = resistivity (ohm m) (log scale).

sandstones and finer-grained siliciclastics dominated from sponge spiculites and radiolarian tests settled
sedimentation of the interval diluting the deposition of into the deep, anoxic basin, remained undisturbed,
organic material. These units have more limited source and were preserved. The resulting deposits were very
rock potential than the Wolfcamp A and B. thinly bedded silica-rich, organic-rich sedimentary fa-
The Wolfcamp A and B were deposited in a deep cies. Carbonates were formed on the shelves and plat-
basin with limited open-ocean circulation. Silica forms. In the more transitional system tract, Wolfcamp

1130 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 B carbonates shed from the platform in debris flows mudstone facies which preserved organic mate-
and sometimes massive slumps. The debrites are rial, typically much leaner than the Wolfcamp A and
amalgamated, massively bedded units with shelf B. These systems repeat from the basal siliciclastic
carbonate clasts in a very fine-grained lime matrix. capped by carbonate repeatedly for the third, second,
These facies have low TOC, low porosity, and few and first Bone Spring as deposited. The Avalon is a
natural fractures. A maximum flooding surface, fourth lowstand fan system productive in the more
condensed shale, separates the Wolfcamp A and B siliciclastic northern basin floor that pinches out along
(Figure 16). The Wolfcamp A is higher-stand, more the updip slope. An upper Cutoff Formation and some
distal environment. The Wolfcamp A and Wolf- shales in the overlying Brushy Canyon (Guadalupian)
camp X-Y sandstones, a unit above the Wolfcamp appear to be potential source rock quality. Hydrocar-
A, are Leonardian. bons generated contribute to intraformation produc-
The carbonate debris flows in the Wolfcamp A tion in the Delaware Basin, conventional sandstone
are thinner-bedded turbidities. Within the Wolfcamp reservoirs in the Delaware Mountain Group, and
A there are fewer massive debrites and a more uni- hydrocarbons migrated updip into central basin plat-
form distribution of interbedded organic-rich silica form and northwest shelf conventional reservoirs.
facies and carbonate turbidite beds (Fairhurst and
Hamlin, 2018). These units are highly naturally
fractured. The natural fractures cut across the thinly Maturation and Migration
interbedded organic-rich silica and carbonate turbi-
dite facies and are more abundant in the organic-rich The Simpson cratonic sandstone play is productive
facies (Fairhurst et al., 2012; Fairhurst and Hanson, on the central basin axis. Inferred from the Wood-
2013). ford petroleum system maturity, the Simpson system
In the Midland Basin, the Wolfcamp B is the is mature enough to account for the 103 million bbl
primary horizontal target, with 61% (4042 wells of oil produced (Dutton et al., 2005a) from this play
[drilled and completed]) compared to 39% (2613 on the central basin axis. Based on the Woodford
wells) in the Wolfcamp A. In the Delaware Basin, petroleum system in the Delaware and Midland
the Wolfcamp A is the primary target with 81% Basins, the Simpson petroleum system is gas prone
(3884 wells [drilled and completed]) compared to in the Delaware Basin, accounting for the high
19% in the Wolfcamp B (912 wells). These figures Ellenburger conventional production in those fields
are through the first quarter of 2020 (F. R. Male, and the 1.7 billion bbl of oil in Ellenburger tradi-
2020, personal communication). The organic-rich, tional reservoirs in the rest of the West Texas Super
silica-rich facies in the 1000-ft-thick Wolfcamp A Basin.
and B shale are the source for the Wolfcamp uncon- The Woodford petroleum system maturation is
ventional resource play and many mixed oils sources on shown in two interpretation maps. First (Figure 17)
the central basin platform and shelf areas to the north from Jarvie et al. (2017) is the vitrinite reflectance
and east, including the Horseshoe atoll, a Pennsylvanian map: Permian Basin shows the Delaware Basin Wood-
reservoir. ford petroleum system in the dry and wet-gas window,
the Midland Basin and northwest shelf in the oil
window, and the central basin platform and northern
Mid-Permian (Leonardian and Guadalupian) Midland Basin in the early mature stage. The sec-
Petroleum Systems ond (Figure 18; Fairhurst, 2015) took Broadhead’s
The Bone Spring Formation in the Delaware Basin (2010) production index from pyrolysis data, created
has been buried deep enough to reach early-maturity the regression of that data to depth, and multiplied
to midlate oil maturities (based on gas–oil ratios that function to the top of the Woodford structure
[GORs]). The Bone Spring is a series of lowstand map. That also shows the Delaware Basin in the dry
siliciclastic “laterally continuous submarine fan sys- to the wet-gas window, Midland Basin and northwest
tems” deposited on the basin floor (Nance and Hamlin, shelf at peak oil maturity, and the central basin axis
2020, p. 346). Carbonate members were deposited and eastern shelf in the early mature stage. The
during highstand. Both have laterally continuous Barnett petroleum system maturity estimates are

Fairhurst et al. 1131

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 17. Vitrinite reflectance map, West Texas Super Basin Woodford petroleum system modified from Jarvie et al. (2017).

based on the close vertical and stratigraphic rela- Texas Super Basin to account for the thermal mat-
tionships to the Woodford petroleum system. That uration of these systems. Figure 19 illustrates these
and its source type and quality have been grouped petroleum systems’ migration pathways, most sig-
similarly by others (Echegu, 2013). nificant for the central basin axis, northwest shelf,
The Wolfcamp A and B petroleum systems are northern Midland Basin, and eastern shelf conven-
early mature to peak-oil and early gas-condensate tional reservoirs.
thermal maturation. These are based on proprietary,
confidential information, production, GORs, and
other data (Party, 2020). CONVENTIONAL RESERVOIRS
Continued subsidence of the West Texas Super
Basin during the Mesozoic is necessary for burial Leonardian and Guadalupian
depths sufficient for the maturation of these petro-
leum systems. The Triassic and Cretaceous sediments Leonardian and Guadalupian conventional reservoirs
thicken from west to east, thickest over the Midland have produced 71% (20.5 billion bbl of oil) of the
Basin (Figure 9A). Eastern tilting was developed resources from all conventional resources (28.9 bil-
during western, Rocky Mountain uplift and devel- lion bbl of oil) in the West Texas Super Basin
opment. The initiation of organic material maturation (Dutton et al., 2005a). These reservoirs are typically
and hydrocarbons generation was in the early to late most abundant on the shelf-crest, lower shelf to
Permian for the Barnett and Woodford and the Early upper slope break, where reservoir development is
Triassic for the central basin axis Simpson Group and maximized (Kerans and Ruppel, 2020) and be-
Wolfcampian petroleum systems (Echegu, 2013). It comes a focus of hydrocarbon migration from the
is estimated that approximately 5000 ft of additional deeper basin (Figure 19). Low-sulfur source cor-
Mesozoic, likely Cretaceous sediments, were de- relations are consistent with the deeper basin (more
posited and subsequently eroded over the West siliciclastic-rich sediment) source. High-sulfur source

1132 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 18. Production index map for the West Texas Super Basin Woodford petroleum system modified from Fairhurst (2015). (A) Plot
and regression model for productivity index by depth to the top of the Woodford (R2 = the proportion of the variance defined by the linear
regression model for the productivity index is valid at the 95% level of confidence [Daniel, 1977; Arkin and Colton, 1963]). (B) Productivity
Index regression model multiplied by the structural subsea depth to the top of the Woodford Shale. The Whiting KCC 503H well on the
central basin platform confirms the early mature stage of maturation for the Woodford petroleum system at that location (Parker et al.,
2014). Apache’s Alpine high area is in the gas-condensate window. FMTOPS, WDFD [GDS], and WDFDPERMIAN.GRD = mapping software
terms.

Fairhurst et al. 1133

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 19. West-east cross-section model (Echegu, 2013) illustrating generation, expulsion, and migration for five petroleum
systems originally from Shumaker (1992). ORD = Ordovician; PENN = Pennsylvanian; PS = petroleum system; Sh = Shale; SIL =
Silurian.

correlations are consistent with shallower depth Figure 19 again shows the focus of hydrocarbon
and deposition environments (more carbonate-rich migration from multiple petroleum systems from the
sediment) on the central basin platform and basin steep eastern flank of the Delaware Basin and the
shelf areas. western margin of the central basin axis into these
Figure 20 shows the Leonardian (Abo, Wichita, overlying conventional reservoir systems. The east-
Lower Clear Fork, Tubb, Middle Clearfork, Upper ern flank of the Delaware Basin to the basin center is
Clear Fork, and Glorieta) conventional fields set up approximately 6 mi. The distance from the basin
on the shelves and platforms proximal to the focus of center to an equal position on the western flank is 40
low-sulfur hydrocarbons from the deeper Midland and to 50 mi depending on the stratigraphic level. On the
Delaware Basins and higher-sulfur hydrocarbons from Delaware Basin eastern flank, more than 25,000 ft of
the shelf and platform. These reservoirs have produced Paleozoic sediments with three world-class petro-
5.2 billion bbl of oil (Dutton et al., 2005a); 18% of the leum systems (Woodford, Barnett, Wolfcamp) and
total basin convention reservoir production. one additional petroleum system (mid-Permian) are
Figure 21 shows the Guadalupian (Queen, Seven structurally lower and steeply inclined. Hydrocarbons
Rivers, and Yates) conventional fields. Together with generated and have been expelled, in the deep basin,
the San Andres and Tansill, representing 15.3 billion migrated upward into the shelf or platform crest
bbl of oil (Dutton et al., 2005a), it is 53% of the conventional reservoirs (Figures 19–22). It is impor-
total basin conventional reservoir production, enough, tant to note the thick Woodford, Barnett, and Wolf-
based on production to date only, to qualify as three camp source rock sections along this western margin
super basins from just these reservoirs. of the central basin axis, central basin platform, and

1134 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 20. Index map of West Texas Super Basin major Leonardian carbonate platform reservoirs. 2-D = two-dimensional.

eastern margin of the Delaware Basin (Figure 7). The hydrocarbons. The volume of oil produced in these
relationship between the Guadalupian (Queen, Seven reservoirs was likely sourced by the Wolfcamp pe-
Rivers, and Yates) conventional fields (Figure 21) on troleum system directly beneath. The Spraberry in
the western margin of the central basin platform and the northern Midland Basin (darker green in Figure
steeply dipping petroleum systems below and into 23) and Dean (purple) are traditional sandstone
those reservoirs (Figures 7, 19) is perhaps the most reservoirs. The Spraberry trend, a larger area to the
significant petroleum system relationship of the entire south (light green in Figure 23), has lower porosity
West Texas Super Basin conventional reservoir re- and permeability and is a fine-grained sandstone to
serves and production. Platform sources, typically siltstone, and production from conventional reser-
recognized by the higher-sulfur content, also contrib- voir completion techniques abruptly declined to sub-
ute to production along this boundary. economic rates. The Leonardian, Spraberry, and Dean
The Guadalupian shelf-crest carbonate reser- are subdivided into an upper and lower Spraberry and
voir (Figures 21, 22) built up, out, and over, slightly Dean (Figure 2A). The siliciclastic very-fine-grained
basinward over time on the central basin platform sandstone and siltstone reservoirs are interpreted as
developed by the Wolfcampian (Figure 10). The submarine, basin-floor fan complexes deposited
Guadalupian fields defined by well density in by debris flows, turbidity currents, and slumps and
Figure 10A occur on the western margin of the suspension (Handford, 1981; Montgomery et al.,
central basin platform west of the Upper Missis- 2000; Dutton et al., 2005a; Nance and Hamlin,
sippian through Pennsylvanian subbasins and the 2020). These interconnected fans formed a produc-
western margin of the Mississippian–Pennsylvanian tive area of 2500 mi2, approximately 75 mi long,
central basin axis margin. north-south, and 35 mi wide, east-west. The updip
The mid-Permian petroleum system in the limit is the north-northeast source area truncated by
Midland Basin (Spraberry; Figure 23) and central the Leonardian shelf margin. The regional Spraberry
basin axis are too immature to have generated trend is not a conventional reservoir and geologic

Fairhurst et al. 1135

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 21. Index map of West Texas Super Basin Major Guadalupian carbonate platform reservoirs (green). For cross section BB9, see
Figure 22.

1136 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 22. West-southwest to east-northeast idealized cross section BB9 (see location in Figure 21) of Leonardian through Guadalupian
carbonate platform reservoirs on the western central basin platform. The North Ward–Estes field is a combination trap in the Queen,
Seven Rivers, and Yates shelf-crest platform carbonates and is laterally equivalent inner shelf evaporates. The Byrd field is an isolated
structure basinward of the shelf crest. Basinal Leonardian, Bone Spring carbonates, basal siliciclastics, and Guadalupian Delaware
Mountain Group, mostly lowstand siliciclastics, are shown to the west-southwest. Alb = Albany.

trap. It is a transitional, fine- to very-fine-grained, low thermal maturity values based on vitrinite re-
conventional resource reservoir to unconventional flectance in the Woodford petroleum system (Figure
resource play. It is a basin-floor–fractured, hydrocarbon- 17). Note that the thermal maturity minimum in the
saturated reservoir with tight porosity and perme- Woodford petroleum system (Figure 17) and similar
ability. The first unconventional resource play in the position of the mature to immature Wolfcamp pe-
West Texas Basin was drilled and produced decades troleum system is coincident with the Breedlove
before the unconventional resource reservoir termi-
trend (Andector shear) in Figure 4 and the magnetic
nology. Production declines are similar to other un-
front of the Llano deformation (dashed line in
conventional resource plays, with high initial rates
Figure 5) and Abilene gravity minimum.
and rapid decline. From the 1950s to 1990s, there
Produced oils in the Horseshoe atoll have been
were 27,114 vertical wells drilled into the Spraberry
identified as the Wolfcamp (Echegu, 2013), which is
in the Midland Basin. Secondary, water-flood recov-
not thermally mature in that area. Migration of
ery efforts started during the early 1950s were eco-
nomically unsuccessful because of the limited, tight mature oil from the Wolfcamp petroleum system
reservoir conductivity between wells. Horizontal had to have migrated over 25 mi and greater dis-
drilling in the 1980s also proved to be financially un- tances from the mature Wolfcamp petroleum system
successful (Montgomery et al., 2000). Thus, the play to the south for the Horseshoe atoll’s reservoirs to
became known as the world’s largest uneconomic oil produce 2.7 billion bbl of oil through 2000. The
field. interpretations based on vitrinite reflectance are con-
sidered with caution. However, the general trends are
consistent with the production index values from
Pennsylvanian
pyrolysis (Figure 18). Hopefully, more thorough pe-
The Horseshoe atoll in the northern Midland Basin troleum system work completed and currently being
(Figure 23) accounts for 71% of all Pennsylvanian undertaken will be published and provide more
conventional reservoir production (Dutton et al., complete analyses and interpretations of these pe-
2005a) in the West Texas Super Basin. This area has troleum systems.

Fairhurst et al. 1137

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 23. Map of Midland Basin, surrounding platforms, and basins, showing oil-producing Leonardian basinal lithofacies (platform
production not shown). Generalized structural contours (subsea) top of Spraberry from Hamlin and Baumgardner (2012, 2020). The platform
outlines are modified from Dutton et al. (2005a); Horseshoe atoll outline from Vest (1970). Fm = Formation; MSL = mean sea level.

1138 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 24. West Texas Super Basin daily oil production from January 1940 through January 2020. MBO/D = million bbl of oil per day.

UNCONVENTIONAL RESOURCES West Texas unconventional reservoir drilling

accounted for 20%–30% of all unconventional oil
Current Production and Status drilling in the United States from January 2007
through 2010 and 30%–35% of all United States
Figure 24 shows the conventional and unconven- unconventional oil reservoir drilling from 2010 to
tional oil production from the West Texas Super 2014. The oil price drop from 2014 to 2016 resulted
Basin from January 1940 to January 2020. Annual in a loss of rigs in all plays, but less in the West Texas
production climbed from 1940 reasonably consis- Super Basin, as the percentage of total unconven-
tently to the peak in 1975 with a fairly continuous tional oil rigs in the West Texas Super Basin rose to
decline until 2006. Conventional and Spraberry pro- 50% of all rigs then to more than 50% during 2019–
duction (the slight amount of unconventional pro- 2020.
duction reported before 2000 in yellow; before 2000 The surprising increases in production, regard-
unconventional oil was not reported separately) in the less of the rig rate, are attributed to the continuous
West Texas Super Basin was below 850,000 BOPD increase in production per rig (Figure 25). The
during 2006, had risen to just over 900,000 BOPD change is relatively consistent from January 2007
during 2009, and increased to more than 4.7 through the end of the third quarter, 2016, to just
million BOPD during 2019. Unconventional re- more than 1000 BOPD per rig added to total basin
source reservoir oil production in the West Texas production at the end of that timeframe. A notice-
Super Basin accounted for just under 90% of total able increase can be seen in total basin production
liquid production in the basin at the close of the per rig from September 2016 through November
decade (2010–2019). West Texas production 2019. This increase in production per rig is likely
peaked in March 2020 at 4.7 million BOPD and caused by the increased horizontal drilling lengths
declined to 4.5 million BOPD during May 2020, per rig, increased proppant, and fluid volumes for
with the rig count falling to half, dropping from completions per linear foot that became the industry
more than 400 to less than 200 during that time. standards during those timeframes. From September

Fairhurst et al. 1139

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Figure 25. West Texas Super Basin oil production rate per rig: January 2007 through January 2021. The monthly production changes per rig are a 3-
month moving average to smooth abrupt monthly changes. The basin’s monthly production data are from the US Energy Information Administration,
and weekly rig counts averaged for each month are from Baker Hughes North American rig count data. R2 = proportion of the variance defined by the
linear regression model for oil production rate change per rig is valid at the 95% level of confidence (Daniel, 1977; Arkin and Colton, 1963).

2016 through July 2017, the rig rate increased from these complicated, heterogeneous petroleum sys-
225 to 375 with a corresponding jump in produc- tems. The solutions for such systems are integrating
tion, averaging 1516 BOPD per active rig. Total many geologic and engineering variables, so most
basin production increased from 2.0 to 2.4 million simplified calculations and models typically provide
BOPD during that time. From August 2017 through an unsatisfactory sufficient solution for these uncon-
November 2018, the rig rate increased from 375 to ventional petroleum systems.
490, and incremental production per rig increased to The US Geological Survey (USGS) assessment
an average of 2542 BOPD as total basin production of undiscovered (undrilled) resources for the Wolf-
increased from 2.4 to 4.6 million BOPD. From camp (19.9 billion bbl of oil and 16.0 TCF of gas
November 2018 through May 2020, the falling rig [TCFG]) and Spraberry (4.2 billion bbl of oil and 3.1
rate and action by producers to reduce production of TCFG) in the Midland Basin is a total of 24.2 billion
existing wells, the rig rate has not increased basin bbl of oil and 19.1 TCFG. In total, 83% of the re-
total production. Total basin production and in- serves from the Wolfcamp is estimated to be in the
creases in production per rig have fallen. Wolfcamp A and B (Gaswirth et al., 2016).
In the Delaware Basin, the USGS has a mean
estimate of 46.3 billion bbl of oil and 281 TCFG. A
Estimated Future Wolfcamp and Leonard total of 60% is in the Wolfcamp A and B and 25% is
Reserves, Midland and Delaware Basins in the Bone Spring. The 93 billion BOE is the largest
continuous resource the USGS has assessed (Gas-
There are multiple values available for estimated wirth et al., 2018). The USGS total estimated mean
ultimate recoverable reserves for the Wolfcamp and undrilled unconventional resources for the Wolf-
Leonard unconventional resource reservoirs in the camp and Leonardian in the West Texas (Permian)
Midland and Delaware Basins. Most are simplified Super Basin is 70.5 billion bbl of oil and 300 TCFG.
volumetric or basic, limited variable input models of The 120 billion BOE estimate is almost twice

1140 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 (191.5%) the 62.67 billion BOE produced from the resource reservoir wells drilled and completed by the
basin through the end of 2019 (Dutton et al., 2005a, industry (F. R. Male, 2020, personal communica-
b; Ruppel, 2019a; New Mexico Oil Conservation tion). The most recent estimates by TORA are 51
Division, 2020; Popova et al., 2020; Railroad Com- billion bbl of oil and 94 TCFG are technically re-
mission of Texas, 2020). coverable from the Wolfcamp A and B in the
The USGS methodology is based on generalized Midland Basin, deep-basin center (Ikonnikova et al.,
geologic and production data and information. It is 2019; Casey, 2020). Technically recoverable is not
not as thorough or complete as the detailed work and the same as the economically recoverable undrilled
models being developed by the Bureau of Economic locations estimated by the USGS. Economically
Geology’s Tight Oil Resource Assessment (TORA) recoverable will be a low percentage of technically
Industrial Consortium that is a continuation of Sloan recoverable at low oil prices and a higher percentage
Foundation and Department of Energy studies with high oil prices and stable to low drilling, com-
completed by the TORA team over the last decade. pletion, and operating costs. The TORA technically
These earlier studies included geologic and reservoir recoverable figure is 250% higher than the USGS
models, economic evaluation, and resource assess- undiscovered (undrilled) estimate in the Midland
ment of the Marcellus, Barnett, Haynesville-Bossier, Basin.
Fayetteville, Eagle Ford, and Bakken now ongoing The TORA estimates are approximately 45 bil-
projects for TORA. The focus on the West Texas lion bbl of oil and 153 TCFG technically recoverable
Super Basin and models has been continuous work from the Wolfcamp A and B in the Delaware Basin
by the TORA Consortium since 2017. (Yang et al., 2019; Casey, 2020), approximately 25%
The TORA process is geologically based, starting higher than the USGS estimate for undiscovered
with decades of research on the cores and outcrop of (undrilled) estimate. The USGS estimate includes the
these unconventional resource reservoirs (Hamlin entire Bone Spring and all Wolfcamp intervals. Fore-
and Baumgardner, 2012). Mineralogical assemblages, casts by TORA in the Delaware Basin only include the
clay, organic material, porosity measured in the lab Wolfcamp A and B. The TORA Industrial Consortia
on the core are models shared with the petrophysi- work and modeling is a continuing, ongoing project
cists measuring and interpreting these variables from and will be reporting other horizons, technically re-
open-hole log suites. That work is completed simul- coverable reserves in the Wolfcampian–Leonardian
taneously with geologists correlating formation and unconventional resource reservoirs for both the
unit tops, and structural, stratigraphic, and sedi- Midland and Delaware Basins in the future.
mentological formation and units throughout the The West Texas Super Basin has benefited from
basin tied to geophysical interpretation. These data a historically extensive infrastructure including sur-
and interpretations, together with engineering variables, face and near subsurface storage and deliverability of
static and dynamic completion, initial measurements, petroleum products, large geologic and engineering
continuous production measurements with operational community, regulatory and public support, open ac-
data, are entered into a Petrel (Schlumberger) 3-D cess, sufficient capital availability, and scalable service
model. These models include data from thousands industry. The paradigm toward new technology in the
of wells in each of the Midland and Delaware Basins. basin has led the industry worldwide. Maintaining
Statistical 3-D modeling of individual variables and talented human resources and capital are challenges
production models based on the geologic and res- that time will tell if individual firms and the industry
ervoir characterization is used to determine original will meet.
hydrocarbon in place, technically and economically
recoverable reserves for the Leonardian through
Wolfcampian (Upper Pennsylvanian) unconven- CONCLUSIONS
tional resource reservoirs (Fairhurst and Dommisse,
2018). The West Texas (Permian) Super Basin is the pro-
The work by TORA to date in the Midland Basin totype super basin. The following have been docu-
has focused on the Wolfcamp A and B since those in- mented: (1) there are multiple petroleum systems,
tervals represent 76% of the horizontal unconventional many linked to other regions or continents; (2) the

Fairhurst et al. 1141

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 geologic architecture and timing of petroleum sys- Emphasis has been placed on the West Texas
tems for generation, migration, and entrapment of Super Basin’s tectonic development from the base-
reserves are ideally developed; (3) this super basin ment through the Cenozoic. The distinction is made
has produced 63 billion BOE to date and has twice between the central basin axis, a tectonic and struc-
that in remaining recoverable reserves; (4) the many tural feature, and the central basin platform, a de-
pays and plays have been outlined; (5) the basin has positional and stratigraphic feature.
substantial infrastructure including geologic community,
regulatory and public support, open access, investment
incentives, and commercial services; (6) talented human REFERENCES CITED
resources and capital will be up to individual firms and
the industry to provide over time; and finally (7) super Adams, D. C., and G. R. Keller, 1996, Precambrian basement
basin thinking, a paradigm toward new technology, has geology of the Permian Basin region of west Texas and
been leading the industry worldwide. eastern New Mexico: A geophysical perspective: AAPG
Bulletin, v. 80, no. 3, p. 410–431.
The West Texas Super Basin petroleum systems Arkin, H., and R. R. Colton, 1963, Tables for statisticians, 2nd
source rocks are low in the system with multiple ed.: New York, Barnes & Noble, 168 p.
successively younger source rocks throughout the Beede, J. W., 1918a, Further notes on the structure near
25,000-ft sedimentary section up to the thousands of Robert Lee, Coke County, Texas, in Further notes on the
structure near Robert Lee, Coke County, Texas [and]
feet of evaporates sealing the entire system. Early
The Marathon Fold and its influence on Petroleum
basin development was gentle subsidence, much like Accumulation: Austin, Texas, The University of Texas
the Williston, Illinois, and Michigan interior cratonic Bulletin 1847D, p. 3–7.
basins. Late Mississippian through early Permian Beede, J. W., 1918b, Notes on the geology and oil possibilities
(Wolfcampian) tectonism formed the large basin- of the northern Diablo Plateau in Texas: Austin, Texas,
The University of Texas Bulletin 1852, 44 p.
scale features, central basin axis, Delaware Basin,
Bickford, M. E., W. R. Van Schmus, K. E. Karlstrom,
Midland Basin, and smaller scale (up to 10 mi in P. A. Mueller, and G. D. Kamenov, 2015, Mesoproterozoic -
length and 5 mi wide) that formed the majority of trans-Laurentian magmatism: A synthesis of continent-
structures necessary for trapping basin-scale hydro- wide age distributions, new SIMS U-Pb ages, zircon
carbon conventional reservoirs. Permian constructive saturation temperatures, and Hf and Nd isotopic com-
positions: Precambrian Research, v. 265, p. 286–312,
carbonate shelf-crest reservoirs were formed on the doi:10.1016/j.precamres.2014.11.024.
central basin platform margins and shelf margins Böse, E., 1917, The Permo-Carboniferous Ammonoids of the
surrounding the deeper Delaware and Midland Ba- Glass Mountains, West Texas, and their stratigraphical
sins. Continued basin subsidence during the Permian significance: Austin, Texas, The University of Texas Bul-
cannot be attributed to ARM and Marathon and letin 1762, 241 p.
Broadhead, R. F., 2004, Petroleum geology of the Tucumcari
Ouachita tectonism alone. Post-ARM tectonic stress, Basin-overview and recent exploration activity: New
later Cretaceous Rocky Mountain deformation, Mexico Geology, v. 26, no. 3, p. 90–94.
and perhaps subsidence of the Pecos-Hobbs mafic Broadhead, R. F., 2010, The Woodford Shale in southeastern
complex caused deep-basin subsidence. Continued New Mexico: Distribution and source rock characteris-
tics: New Mexico Geology, v. 32, no. 3, p. 79–90.
subsidence into the Mesozoic and deposition of
Brown, A., 2019, Post-Permian history of the greater Permian
approximately 5000 ft of additional stratigraphic Basin area, in S. C. Ruppel, ed., Anatomy of a Paleozoic
section, now eroded, is necessary for the depth of basin: The Permian Basin, USA: Austin Texas, The Uni-
burial needed for initiation and peak generation of versity of Texas at Austin, Bureau of Economic Geology
the West Texas Super Basin petroleum systems. Report of Investigations 285 and AAPG Memoir 118, v. 1,
p. 97–134, doi:10.23867/RI0285-1.
The juxtaposition of deep, steeply dipping basin
Brown, L. F. Jr., R. F. Solis-Iriate, and D. A. Johns, 1987, Re-
margins and shelf margin carbonate shelf crests gional stratigraphic cross sections, Upper Pennsylvanian
was ideal for funneling deep-basin petroleum source and Lower Permian strata (Virgilian and Wolfcampian
rock systems and migration from more-proximal Series), north-central Texas: Austin, Texas, Bureau of Eco-
shelf and platform source systems. Over the last nomic Geology 27 p.
Brown, L. F. Jr., R. F. Solis-Iriate, and D. A. Johns, 1990,
decade, the deep-basin source rock systems have Regional depositional systems tracts, paleogeography,
also become the most actively targeted petroleum and sequence stratigraphy, Upper Pennsylvanian and
resource reservoirs in the world. Lower Permian strata, north- and west-central Texas:

1142 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Austin, Texas, Bureau of Economic Geology Report of Eaton, G. P., 1987, Topography and origin of the southern
Investigations 197, 116 p. Rocky Mountains and Alvarado Ridge, in M. P. Coward,
Calle, A. Z., E. Horne, S. Hamlin, and D. Carr, 2019, J. F. Dewey, and P. L. Hancock, eds., Continental ex-
Structure and stratigraphic architecture of the southeast tensional tectonics: Geological Society, London, Special
Delaware Basin, in E. D. Goodman, ed., Tight Oil Re- Publications 1987, v. 28, p. 355–369.
source Assessment Research Consortium Annual Meet- Echegu, S., 2013, Geological and geochemical investigation
ing, Austin, Texas, November 20–21, 2019, p. 15–19. of the petroleum systems of the Permian Basin of west
Casey, B., 2020, Visualization and discussion of recent Texas and southeast New Mexico, Ph.D. dissertation,
southern Midland Basin geologic Modeling: Tight Oil University of Houston, Houston, Texas, 195 p.
Resource Assessment Consortium Annual Meeting, Aus- Ewing, T. E., 1991, The tectonic framework of Texas: Text to
tin, Texas, May 28–29, 2020. accompany “The Tectonic Map of Texas”: Austin, Texas,
Comer, J. B., 1991, Stratigraphic analysis of the Upper De- The University of Texas at Austin, Bureau of Economic
vonian Woodford Formation, Permian Basin, west Texas Geology, 36 p.
and southeastern New Mexico: Bureau of Economic Ewing, T. E., 2016, Texas through time: Lone star geology,
Geology Report of Investigations 201, 63 p. landscapes, and resources: Austin, Texas, The University
Comer, J. B., 2005, Facies distribution and hydrocarbon of Texas at Austin, Bureau of Economic Geology, Udden
production potential of Woodford Shale in the southern Series No. 6, 431 p.
Midcontinent, in B. J. Cardott, ed., Unconventional Ewing, T. E., 2019, Tectonics of the West Texas (Permian)
energy resources in the southern Midcontinent, 2004 Basin–Origins, structural geology, subsidence, and later
Symposium: Norman, Oklahoma, Oklahoma Geological modification, in S. C. Ruppel, ed.,Anatomy of a Paleo-
Survey Circular 110, p. 51–62. zoic basin: The Permian Basin, USA: Austin, Texas, The
Comer, J. B., 2008, Woodford Shale in southern Mid- University of Texas at Austin, Bureau of Economic
continent, USA - Transgressive system tract marine Geology Report of Investigations 285 and AAPG
source rocks on an arid passive continental margin with Memoir 118, v. 1, p. 63–96, doi:10.23867/RI0285-1.
Ewing, T. E., M. A. Barnes, and R. E. Denison, 2019, Pro-
persistent oceanic upwelling (abs.): AAPG Annual Con-
terozoic foundations of the Permian Basin, west Texas
vention, San Antonio, Texas, April 20–23, 2008, accessed
and southeastern New Mexico – A review, in S. C. Ruppel,
June 30, 2014, http://www.searchanddiscovery.com
ed., Anatomy of a Paleozoic basin: The Permian Basin,
/abstracts/html/2008/annual/abstracts/404026.htm.
USA: Austin, Texas, The University of Texas at Austin,
Daniel, W. W., 1977, Introductory statistics with applications:
Bureau of Economic Geology Report of Investigations 285
Boston, Houghton Mifflin, 475 p.
and AAPG Memoir 118, v. 1, p. 43–61, doi:10.23867
Denison, R. E., W. H. Burke, J. B. Otto, and E. A. Hetherington,
/RI0285-1.
1977, Age of igneous and metamorphic activity affecting
Fairhurst, B., 2015, “Stealth” and serendipitous exploration
the Ouachita foldbelt, in C. G. Stone, B. R. Haley,
for the Texas Woodford (abs.): AAPG Education Di-
D. F. Holbrook, N. F. Williams, and J. D. McFarland, eds.,
rectorate, Woodford Shale Forum: Focus on Optimiza-
Symposium on the geology of the Ouachita Mountains:
tion, Oklahoma City, Oklahoma, May 12, 2015, accessed
Little Rock, Arkansas, Arkansas Geological Commission February 27, 2021, http://www.searchanddiscovery.com
Miscellaneous Publication 13, v. 1, p. 25–40. /pdfz/abstracts/pdf/2015/90241ed/abstracts/ndx_fairhurst
Dickerson, P. W., 2003, Intraplate mountain building in re- .pdf.html.
sponse to continent–continent collision—the Ancestral Fairhurst, B., 2016, Resource reservoirs and hydrocarbon
Rocky Mountains (North America) and inferences drawn source rocks defined by depositional time-intervals and
from the Tien Shan (Central Asia): Tectonophysics, tectonic basin type, continental United States: Eighth
v. 365, no. 1–4, p. 129–142, doi:10.1016/S0040- International Symposium on Tight Sandstone and Shale
1951(03)00019-2. Plays Exploration and Development, Chengdu, China,
Dott, R. H., and R. L. Batten, 1976, Evolution of the earth, July 15–17, 2016.
2nd ed.: New York, McGraw-Hill, 504 p. Fairhurst, B., 2018, Resource reservoirs and hydrocarbon
Dutton, S. P., E. M. Kim, R. F. Broadhead, C. L. Breton, source rocks defined by depositional time-intervals and
W. D. Raatz, S. C. Ruppel, and C. Kerans, 2005a, Play tectonic basin type, continental United States, in
analysis and digital portfolio of major oil reservoirs in the B. Fairhurst, ed., Tight Oil Resource Assessment Re-
Permian basin: Application and transfer of advanced search Consortium Annual Meeting, Austin, Texas,
geological and engineering technologies for incremental March 26, 2018, p. 1–14.
production opportunities: Austin, Texas, Bureau of Eco- Fairhurst, B., 2019, The perfect unconventional resource
nomic Geology Report of Investigations 271, 287 p. portfolio: Houston Geological Society Bulletin, v. 62,
Dutton, S. P., E. M. Kim, R. F. Broadhead, W. D. Raatz, no. 2, p. 35–43.
C. L. Breton, S. C. Ruppel, and C. Kerans, 2005b, Play Fairhurst, B., 2020, The perfect unconventional resource
analysis and leading edge oil reservoir development portfolio: Society of Petroleum Engineers/AAPG/Society
methods in the Permian Basin: Increased recovery of Exploration Geophysicists Unconventional Resources
through advanced technologies: AAPG Bulletin, v. 89, Technology Conference, virtual, July 22, 2020, URTEC-
no. 5, p. 553–576, doi:10.1306/12070404093. 2020-2940-MS, 9 p.

Fairhurst et al. 1143

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Fairhurst, B., 2021, West Texas (Permian) Super Basin: Ex- exploration and development: Midland, Texas, West
ploration, discovery, and development of unconventional Texas Geological Society Publication 90-87, p. 15–27.
resources, in R. Merrill, ed., Giant discoveries of the Gaswirth, S. B., K. L. French, J. K. Pitman, K. R. Marra,
decade: 2010-2020: AAPG Memoir 125. T. J. Mercier, H. M. Leathers-Miller, C. J. Schenk et al.,
Fairhurst, B., and R. Dommisse, 2018, Introduction: High- 2018, Assessment of undiscovered continuous oil and gas
lights, additions to TORA and Sponsor Discussion, in resources in the Wolfcamp Shale and Bone Spring For-
B. Fairhurst, ed., Tight Oil Resource Assessment Indus- mation of the Delaware Basin, Permian Basin Province,
trial Consortium Annual Meeting, Austin, Texas, April New Mexico, and Texas: Denver, Colorado, US Geo-
26, 2018. logical Survey Fact Sheet 2018-3073, 4 p.
Fairhurst, B., and S. Hamlin, 2018, Stratigraphic observations Gaswirth, S. B., K. R. Marra, P. G. Lillis, T. J. Mercier,
of the Upper Wolfcampian Shale (A&B), southern H. M. Leathers-Miller, C. J. Schenk, T. R. Klett et al.,
Delaware Basin, West Texas: Variations in stratigraphy, 2016, Assessment of undiscovered continuous oil re-
depositional processes, mineral facies and log measure- sources in the Wolfcamp shale of the Midland Basin,
ments, in B. Fairhurst, ed., Tight Oil Resource Assess- Permian, Basin Province, Texas, 2016: Denver, Colorado,
ment Research Consortium Annual Meeting, Austin, US Geological Survey Fact Sheet S2016-S3092., 4 p.
Texas, March 26, 2018, p. 91–109. Goldman, D., S. M. Bergström, and C. E. Mitchell, 1995,
Fairhurst, B., and M. L. Hanson, 2013, Wolfbone oil- Revision of the Zone 13 graptolite biostratigraphy in the
saturated, super sweet spot, southern Delaware Basin: Marathon, Texas, standard succession and its bearing on Upper
Integrated approach from exploration to geologic/ Ordovician graptolite biogeography: Lethaia, v. 28, no. 2,
reservoir modeling and field development: Unconven- p. 115–128, doi:10.1111/j.1502-3931.1995.tb01601.x.
tional Resources Technology Conference, Denver, Col- Gradstein, F. M., J. G. Ogg, M. D. Schmitz, and G. M. Ogg,
orado, August 12–14, 2013, 10 p. 2012, The geologic time scale 2012: Cambridge, United
Fairhurst, B., M. L. Hanson, F. Reed, and N. Pieracacos, 2012, Kingdom, Cambridge University Press, 1144 p.
Wolfbone play evolution, southern Delaware Basin: Geo- Grunau, H. R., 1983, Abundance of source rocks for oil and
logic concepts modifications that have enhanced economic gas worldwide: Journal of Petroleum Geology, v. 6, no. 1,
success: AAPG Search and Discovery article 10412, ac-
p. 39–53, doi:10.1111/j.1747-5457.1983.tb00261.x.
cessed June 23, 2013, http://www.searchanddiscovery.com
Hamlin, H. S., and R. W. Baumgardner, 2012, Wolfberry
/documents/2012/10412fairhurst/ndx_fairhurst.pdf.
(Wolfcampian-Leonardian) deep-water depositional sys-
Fairhurst, B., and B. Lindsay, 2020, History of geologic con-
tems in the Midland Basin: Stratigraphy, lithofacies, reser-
cepts that opened exploration and development of the West
voirs, and source rocks: Austin, Texas, Bureau of Economic
Texas (Permian) Basin 1915-1925: Midland, Texas, West
Geology Report of Investigations 277, 61 p.
Texas Geological Society Annual Meeting, September 23,
Hamlin, H. S., and R. W. Baumgardner Jr., 2020, Lower
2020, 2 p.
Permian (Leonardian) deepwater successions in the
Fairhurst, B., and H. Rogers, 2018, Permian Basin reconstruc-
Midland Basin: Lithofacies, stratigraphy, reservoirs, and
tion: Tectonic and stratigraphic relationships Cambrian
source rocks, in S. C. Ruppel, Anatomy of a Paleozoic
through Pennsylvanian, in B. Fairhurst, ed., Tight Oil
basin: The Permian Basin, USA: Austin Texas, Bureau of
Resource Assessment Research Consortium Annual
Meeting, Austin, Texas, November 1–2, 2018, p. 55–61. Economic Geology Report of Investigations 285 and
Fritz, R. D., and J. R. Mitchell, 2021, The Anadarko “Super” AAPG Memoir 118, v. 2, p. 283–320.
Basin: 10 key characteristics to understand its unique pro- Handford, C. R., 1981, Sedimentology and genetic stratig-
ductivity: AAPG Bulletin, v. 105, no. 6, p. 1199–1231, raphy of Dean and Spraberry Formations (Permian),
doi:10.1306/03242120082. Midland Basin, Texas: AAPG Bulletin, v. 20, no. 9,
Fryklund, R., and P. Stark, 2020, Super basins—New para- p. 1602–1616.
digm for oil and gas supply: AAPG Bulletin, v. 104, Hanson, R. E., R. E. Puckett Jr., G. R. Keller, M. E. Brueseke,
no. 12, p. 2507–2519, doi:10.1306/09182017314. C. L. Bulen, S. A. Mertzman, S. A. Finegan, and
Fu, Q., R. W. Baumgardner Jr., and H. S. Hamlin, 2020, Early D. A. McCleery, 2013, Intraplate magmatism related to
Permian (Wolfcampian) succession in the Permian Basin: opening of the southern Iapetus ocean: Cambrian Wichita
Icehouse platform, slope carbonates, and basinal mud- igneous province in the Southern Oklahoma rift zone:
rocks, in S. C. Ruppel, ed., Anatomy of a Paleozoic basin: Lithos, v. 174, p. 57–70, doi:10.1016/j.lithos.2012.06.003.
The Permian Basin, USA: Austin, Texas, The University of Henderson, C. M., V. I. Davydov, and B. R. Wardlaw, 2012,
Texas at Austin, Bureau of Economic Geology Report of In- The Permian period, in F. M. Gradstein, J. G. Ogg,
vestigations 285 and AAPG Memoir 118, v. 2, p. 185–225. M. D. Schmitz, and G. M. Ogg, eds., The geologic time
Galley, J. E., 1958, Oil and geology in the Permian Basin of scale 2012: Oxford, United Kingdom, Elsevier, p. 653–679,
Texas and New Mexico, in L. G. Weeks, ed., Habitat of doi:10.1016/B978-0-444-59425-9.00024-X.
oil: AAPG Special Publication, p. 395–446. Horak, R. L., 1985, Trans-Pecos tectonism and its effect on the
Gardiner, W. B., 1990, Fault fabric and structural sub- Permian Basin, in P. W. Dickerson and W. R. Muehlberger,
provinces of the Central Basin Platform: A model for eds., Structure and tectonics of trans-Pecos Texas:
strike-slip movement, in J. E. Flis and R. C. Price, eds., Midland, Texas, West Texas Geological Society Publi-
Permian Basin oil and gas fields: Innovative ideas in cation 85-81, p. 81–87.

1144 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Ikonnikova, S., H. S. Hamlin, Q. Yang, V. del Carpio Neyra, Texas [and] The Marathon Fold and its influence on
G. Gulen, and B. Fairhurst, 2019, Individual well pro- petroleum accumulation: Austin, Texas, The University
ductivity and profitability of Midland Wolfcamp A and B of Texas Bulletin 1847D, p. 9–16.
wells, in B. Fairhurst, ed., Tight Oil Resource Assessment Liddle, R. A., and Prettyman, T. M., 1918, Geology and
Research Consortium Annual Meeting: Austin, Texas, mineral resources of Crockett County with notes on the
November 1–2, 2019, p. 89–96. stratigraphy, structure, and oil prospects of the Central
Jarvie, D. M., D. Prose, B. M. Jarvie, R. Drozd, and Pecos Valley: Austin, Texas, The University of Texas
A. Maende, 2017, Conventional and unconventional Bulletin 1857, 97 p.
petroleum systems of the Delaware Basin: Search and McKee, E. D., and S. S. Oriel, 1967, Paleotectonic investi-
Discovery article 10949, accessed April 30, 2020, http:// gations of the Permian system in the United States: Re-
www.searchanddiscovery.com/documents/2017/10949jarvie ston, Virginia, US Geological Survey Professional Paper
/ndx_jarvie.pdf. 515, 271 p., doi:10.3133/pp515.
Jones, R. H., 2005, The Middle-Upper Ordovician Simpson Montgomery, S. L., D. S. Schechter, and J. Lorenz, 2000,
Group of the Permian Basin: Deposition, diagenesis, and Advanced reservoir characterization to evaluate carbon
reservoir development: Austin, Texas, Bureau of Eco- dioxide flooding, Spraberry trend, Midland Basin, Texas:
nomic Geology, The University of Texas at Austin, 41 p. AAPG Bulletin, v. 84, no. 9, p. 1247–1273.
Katz, B. J., V. D. Robison, W. C. Dawson, and L. W. Elrod, Mulder, J. A., K. E. Karlstom, K. Fletcher, M. T. Heizler,
1994, Simpson–Ellenburger petroleum system of the J. M. Timmons, L. J. Crossey, G. E. Gehrels, and
Central Basin Platform, West Texas, U.S.A, in L. B. Magoon M. Pecha, 2017, The syn-orogenic sedimentary record
and W. G. Dow, eds., The petroleum system–From source of the Grenville Orogeny in southwest Laurentia:
to trap: AAPG Memoir 60, p. 453–461. Precambrian Research, v. 294, p. 33–52, doi:10.1016
Keller, G. R., J. M. Hills, M. R. Baker, and E. T. Wallin, 1989, /j.precamres.2017.03.006.
Geophysical and geochronological constraints on the Nance, H. S., and H. S. Hamlin, 2020, The Bone Spring
extent and age of mafic intrusions in the basement of Formation (Leonardian) of the Delaware Basin: Deep-
west Texas and eastern: New Mexico Geology, v. 17,
water lithofacies and stratigraphy, in S. C. Ruppel, ed.,
no. 11, p. 1049–1052, doi:10.1130/0091-7613(1989)
Anatomy of a Paleozoic Basin: The Permian Basin, USA,
017<1049:GAGCOT>2.3.CO;2.
vol. 2: Austin, Texas, The University of Texas at Austin,
Kerans, C., and S. C. Ruppel, 2020, Composite and high-
Bureau of Economic Geology Report of Investigations
frequency cyclicity in Middle Permian shelf carbonates:
285; AAPG Memoir 118, p. 319–348.
The San Andres and Grayburg (Guadalupian) succession
New Mexico Oil Conservation Division, 2020, accessed May
in the Permian Basin, in S. C. Ruppel, ed., Anatomy of a
15, 2020, http://www.emnrd.state.nm.us/ocd.
Paleozoic basin; The Permian Basin, USA, volume 2:
Nicholas, R. L., 1983, Devils River uplift, in E. C. Kettenbrink
Austin, Texas, The University of Texas at Austin, Bureau
Jr., ed., Stratigraphy and structure of the Val Verde Basin –
of Economic Geology Report of Investigations 285;
Devils River uplift, Texas: Midland, Texas, West Texas
AAPG Memoir 118, p. 349–398.
Geological Society Publication 83-77, p. 125–137.
King, P. B., 1942, Permian of west Texas and southeastern
Nicholas, R. L., and D. E. Waddell, 1989, The Ouachita
New Mexico: AAPG Bulletin, v. 26, no. 4, p. 535–649.
King, P. B., 1948, Geology of the southern Guadalupe system in the subsurface of Texas, Arkansas, and Loui-
Mountains, Texas: Reston, Virginia, US Geologic Survey siana, in R. D. Hatcher Jr., W. A. Thomas, and G. W.
Professional Paper 215, 183 p. Viele, eds., The Appalachian-Ouachita orogen in the
King, P. B., 1977, The evolution of North America, revised United States: The geology of North America: Boulder,
ed.: Princeton, New Jersey, Princeton University Press, Colorado, Geological Society of America, v. F-2, p. 661–672.
197 p., doi:10.1515/9781400868490. Parker, A., D. Entzminger, J. Leone, M. Sonnenfeld, and
Klemme, H. D., and G. F. Ulmishek, 1991, Effective petro- L. Canter, 2014, Lessons learned from the KCC #503H
leum source rocks of the world: Stratigraphic distribution Woodford horizontal well at Keystone South field, Winkler
and controlling depositional factors: AAPG Bulletin, County, TX: AAPG Search and Discovery article 20254,
v. 75, no. 12, p. 1809–1851. accessed August 13, 2014, http://www.searchanddiscovery
Kluth, C. F., 1986, Plate tectonics of the ancestral Rocky .com/documents/2014/20254parker/ndx_parker.pdf.
Mountains, in J. A. Peterson, ed., Paleotectonics and Party, M. J., 2020, Permian Basin: Barnett Shale play emerges:
sedimentation in the Rocky Mountain Region, United AAPG, Global Super Basins Leadership Conference,
States: AAPG Memoir 41, p. 353–369, doi:10.1306 Sugar Land, Texas, February 11–13, 2020, accessed February
/M41456C17. 27, 2021, https://www.aapg.org/videos/super-basins/articleid
Leary, R. J., P. Umhoefer, M. E. Smith, and N. Riggs, 2017, A /56496/mike-party-permian-basin-barnett-shale-play-
three-sided orogen: A new tectonic model for Ancestral emerges.
Rocky Mountain uplift and basin development: Geology, Perry, W. J., 1989, Tectonic evolution of the Anadarko Basin
v. 45, p. 735–738, doi:10.1130/G39041.1. region, Oklahoma: Reston, Virginia, US Geological Survey
Liddle, R. A., 1918, The Marathon Fold and its influence on Bulletin 1866-A, 19 p.
petroleum accumulation in J. W. Beede, ed., Further Phillips, W. B., 1901, Texas petroleum: Austin, Texas, The
notes on the structure near Robert Lee, Coke County, University of Texas Mineral Survey Bulletin 1, 101 p.

Fairhurst et al. 1145

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Phillips, W. B., 1902, Report of progress for 1901. Sulphur, Paleozoic Basin: The Permian Basin, USA, volume 1:
oil and quicksilver in Trans-Pecos: Austin, Texas, The Austin, Texas, The University of Texas at Austin, Bu-
University of Texas Mineral Survey Bulletin 9, 43 p. reau of Economic Geology Report of Investigations 285;
Pioneer Natural Resources, 2013, Independent Petroleum AAPG Memoir 118, p. 379–399.
Association of America Oil and Gas Investment Sym- Ruppel, S. C., S. D. Hovorka, and R. Barnaby, 2020b,
posium, New York, April 16, 2013, 17 p. Proximal shallow-water carbonates and distal biosili-
Pope, M. C., 2004, Cherty carbonate facies of the Montoya ceous cherts of the Lower Devonian Thirtyone Forma-
Group, southern New Mexico and western Texas and its tion, Permian Basin, in S. C. Ruppel, ed., Anatomy of a
regional correlatives: A record of Late Ordovician pale- Paleozoic Basin: The Permian Basin, USA, volume 2:
oceanography on southern Laurentia: Palaeogeography, Austin, Texas, The University of Texas at Austin, Bureau
Palaeoclimatology, Palaeoecology, v. 210, no. 2–4, p. 367– of Economic Geology Report of Investigations 285;
384, doi:10.1016/j.palaeo.2004.02.035. AAPG Memoir 118, p. 37–74.
Popova, O., E. Geary, A. Patel, G. Long, J. Little, S. Grape, Ruppel, S. C., H. Rowe, R. M. Reed, J. E. Barrick, E. J. James,
and E. Panarelli, 2020, Cross-comparison of stacked and R. G. Loucks, 2020c, The Woodford Formation of
unconventional plays of Delaware and Appalachian Ba- the Permian Basin: Regional, Middle to Late Devonian
sins: Reservoir characteristics and production profiles: transgression of the southern Midcontinent and accom-
AAPG Search and Discovery article 11342, accessed panying global anoxia, in S. C. Ruppel, ed., Anatomy of
February 11, 2021, http://www.searchanddiscovery.com a Paleozoic Basin: The Permian Basin, USA, volume 2:
/documents/2020/11342popova/ndx_popova.pdf. Austin, Texas, The University of Texas at Austin, Bureau
Powers, S., 1927, Buried ridges in west Texas: AAPG Bul- of Economic Geology Report of Investigations 285;
letin, v. 11, no. 10, p. 1109–1115. AAPG Memoir 118, p. 75–124.
Pratt, W. E., 1921, The present excitement at Fort Stockton, Ruppel, S. C., H. Rowe, R. M. Reed, and R. G. Loucks,
Texas: AAPG Bulletin, v. 5, no. 1, p. 88–89. 2020d, The Mississippian System in the Permian Basin:
Railroad Commission of Texas, 2020, accessed June 15, 2020, Proximal platform carbonates and distal organic-rich
http://rrc.state.tx.us/oil-gas/research-and-statistics/production- mudrocks, in S. C. Ruppel, ed., Anatomy of a Paleo-
data/historical-production-data. zoic Basin: The Permian Basin, USA, volume 2: Austin,
Richardson, G. B., 1904, Reconnaissance of Trans-Pecos Texas, The University of Texas at Austin, Bureau of
Texas: North of the Texas and Pacific Railway: Bulletin Economic Geology Report of Investigations 285; AAPG
of the University of Texas n. 23, 119 p. Memoir 118, p. 125–158.
Rodriguez, E., P. W. Dickerson, and D. F. Stockli, 2017, New Shumaker, R. C., 1992, Paleozoic structure of the Central
zircon U-Pb age constraint of the origin of the Devils Basin Uplift and adjacent Delaware Basin, west Texas:
River uplift (SW Texas) and insights into the late Pro- AAPG Bulletin, v. 76, no. 11, p. 1804–1824.
terozoic and Paleozoic evolution of the southern margin Sloss, L. L., 1963, Sequences in the cratonic interior of North
of Laurentia (abs.): American Geophysical Union, Fall America: GSA Bulletin, v. 74, no. 2, p. 93–114, doi:
Meeting 2017, New Orleans, Louisiana, December 10.1130/0016-7606(1963)74[93:SITCIO]2.0.CO;2.
11–15, 2017, EP53B-1732, 1 p. Sloss, L. L., 1988, Tectonic evolution of the craton in Phaner-
Roen, J. B., 1984, Geology of the Devonian black shales of the ozoic time, in L. L. Sloss, ed., Sedimentary cover–North
Appalachian Basin: Organic Geochemistry, v. 5, no. 4, American Craton: The geology of North America: Boulder,
p. 241–254, doi:10.1016/0146-6380(84)90011-1. Colorado, Geological Society of America, v. D-2, p. 25–51,
Ross, C. A., 1963, Standard Wolfcampian Series (Permian), doi:10.1130/DNAG-GNA-D2.25.
Glass Mountains, Texas, in C. A. Ross, ed., Standard Sorkhabi, R., 2009, Rich petroleum source rocks: GeoExPro,
Wolfcampian Series (Permian), Glass Mountains, Texas: v. 6, no. 6, 15 p.
Boulder, Colorado, Geological Society of America Spencer, C. J., A. R. Prave, P. A. Cawood, and N. M. W. Roberts,
Memoir 88, 205 p., doi:10.1130/MEM88-p1. 2014, Detrital zircon geochronology of the Grenville/Llano
Ross, J. R., and C. A. Ross, 1992, Ordovician sea-level fluc- foreland and basal Sauk sequence in west Texas, USA:
tuations, in B. D. Webby and Laurie, J. R., eds., Global Geological Society of America Bulletin, v. 126, no. 7–8,
perspectives on Ordovician geology: Proceedings of the p. 1117–1128, doi:10.1130/B30884.1.
Sixth Annual International Symposium on the Ordovician, Sternbach, C. A., 2020, Super basin thinking: Methods to
University of Sydney, Australia, July 15–19, 1991, explore and revitalize the world’s greatest petroleum
p. 327–335. basins: AAPG Bulletin, v. 104, no. 12, p. 2463–2506,
Ruppel, S. C., 2019a, Introduction, overview, and evolution, doi:10.1306/09152020073.
in S. C. Ruppel, ed., Anatomy of a Paleozoic Basin: The Tai, P.-C., and S. L. Dorobek, 2000, Tectonic model for Late
Permian Basin, USA, volume 1: Austin, Texas, The Uni- Paleozoic deformation of the Central Basin Platform,
versity of Texas at Austin, Bureau of Economic Geology Permian Basin region, West Texas, in W. D. DeMis, M.
Report of Investigations 285; AAPG Memoir 118, p. 1–27. K. Nelis, and R. C. Trentham, eds., The Permian Basin:
Ruppel, S. C., 2019b, The Fusselman of the Permian Basin: Proving ground for tomorrow’s technologies: West Texas
Patterns in depositional and diagenetic facies development Geological Society Fall Symposium, October 19–20,
on a stable platform during the Late Ordovician–Early 2000: Midland, Texas, West Texas Geological Society,
Silurian icehouse, in S. C. Ruppel, ed., Anatomy of a p. 157–176.

1146 Tectonics, Structural Development, Sedimentation, and Petroleum Systems

Downloaded from http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
by William Fairhurst
 Thomas, W. A., 2014, The southern Oklahoma transform- Whaley, J., 2019, Petroleum geology: What is a Super Basin?:
parallel intracratonic fault system, in N. H. Suneson, ed., GEO ExPro, v. 16, no. 5, p. 60–64.
Igneous and tectonic history of the Southern Oklahoma Wilde, G. L., 1990, Practical fusulinid zonation–The species
aulacogen: Norman, Oklahoma, Oklahoma Geological concept with Permian Basin emphasis: Midland, Texas,
Survey Guidebook 38, p. 375–387. West Texas Geological Society Bulletin 29, p. 5–33.
Udden, J. A., 1915, Potash in the Texas Permian: Austin, Winfree, K. E., 1994, Post-Permian folding and fracturing of
Texas: Bureau of Economic Geology and Technology, the Spraberry and San Andres formations within the
Bulletin of The University of Texas 17, 59 p. Midland Basin region of West Texas, in T. M. Laroche
Udden, J. A., 1917, Notes on the geology of the Glass and J. T. Viveiros, eds., Structure and tectonics of the Big
Mountains: Austin, Texas, The University of Texas Bul- Bend and southern Permian Basin, Texas: Midland,
letin 1753, 59 p. Texas, West Texas Geological Society Publication
Udden, J. A., Baker, C. L., and Böse, E., 1916, Review of the 94–95, p. 189–212.
geology of Texas: Austin, Texas, Bureau of Economic Wright, W. F., 1965, Petroleum geology of the Simpson
Geology and Technology, Bulletin of The University of Group, West Texas and Southeast New Mexico: Tulsa
Texas 44, 164 p. Geological Society Digest, v. 33, p. 62–73.
van Waterschoot van der Gracht, W. A. J. M., 1929, Barrier reefs Wuellner, D. E., L. R. Lehtonen, and W. J. Jones, 1986,
in the West Texas Basin: AAPG Bulletin, v. 13, no. 10, 1 p. Sedimentary-tectonic development of the Marathon-Val
Ver Wiebe, W. A., 1929, Tectonic classification of oil fields in the Verde basins, west Texas, USA: A Permo-Carboniferous
United States: AAPG Bulletin, v. 13, no. 5, p. 409–440. migrating foredeep, in P. A. Allen and P. Homewood,
Vest, E. L. Jr., 1970, Oil fields of Pennsylvanian-Permian eds., Foreland basins: Ghent, Belgium, International
Horseshoe Atoll, west Texas, in M. T. Halbouty, ed., Association of Sedimentologists Special Publication 8,
Geology of giant petroleum fields: AAPG Memoir 14, p. 347–368.
p. 185–203. Yang, K.-M., and S. L. Dorobek, 1995, The Permian Basin of
Wahlman, G. P., and D. R. Tasker, 2014, Lower Permian west Texas and New Mexico: Tectonic history of a
(Wolfcamp) carbonate shelf-margin and slope facies, “composite” foreland basin and its effects on stratigraphic
Central Basin Platform and Hueco Mountains, Permian development, in S. L. Doirobek and G. M. Ross, eds.,
Basin, West Texas, USA, in K. Verwer, T. E. Playton, and Stratigraphic evolution of foreland basins: Tulsa, Okla-
P. M. Harris, eds., Deposits, architecture and controls of homa, SEPM Special Publication 52, p. 149–174, doi:
carbonate margins, slope and basinal settings: Tulsa, 10.2110/pec.95.52.0149.
Oklahoma, SEPM Special Publication 105, p. 305–333. Yang, Q., S. Ikonnikova, A. Gherabati, E. D. Goodman, and
Walper, J. L., 1977, Paleozoic tectonics of the southern G. McDaid, 2019, Delaware Basin Wolfcamp A pro-
margin of North America: GCAGS Transactions, v. 27, ductivity analysis and technically recoverable resources
p. 230–241. production, in E. D. Goodman, ed., Tight Oil Resource
Webby, B. D., R. A. Cooper, S. M. Bergström, and F. Paris, Assessment Research Consortium Annual Meeting,
2004, Stratigraphic framework and time slices, in November 20–21, 2019, p. 58–67.
B. Webby, F. Parris, M. Droser, and I. Percival, eds., The Ye, H., L. Royden, C. Burchfiel, and M. Schuepbach, 1996,
great Ordovician biodiversification event: New York, Late Paleozoic deformation of interior North America:
Columbia University Press, p. 41–47, doi:10.7312 The greater Ancestral Rocky Mountains: AAPG Bulletin,
/webb12678-003. v. 80, no. 9, p. 1397–1432.

Fairhurst et al. 1147

Downloaded fromView
http://pubs.geoscienceworld.org/aapgbull/article-pdf/105/6/1099/5329366/bltn20130.pdf
publication stats
by William Fairhurst