Deterministic Petrophysics
Workflow
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Determin Workflow
• Deterministic Workflow
– Precalculations
– Environmental Corrections
– Parameter Picking
– Volume of Shale
– Porosity
– Water Saturation
– Permeability
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Data Preparation
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Petrophysics Overview
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Determin Workflow
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Petrophysics Philosophy
Definitions
Precalc
Environmental Corrections
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Petrophysical Philosophy
POROSITY CLASSIFICATIONS • Free water = all non
clay bound water
MATRIX DRY CLAY
CLAY BOUND FREE WATER
HYDROCARBONS
(includes SWirr)
WATER (INC. SWIRR)
Quartz • Hydrocarbon occupy
Calcite only non clay pore
Dolomite Ø cbw Ø fw Øh space
V sh Øe • Shale definition
Øt excludes silt
Vrock VSH e 1
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The Precalc module
• Borehole temperature and pressure profiles
• Temperature (FTEMP): TLI/BLI, SONDE, GRADIENT
• Pressure (FPRESS): MUD_DENS, GRADIENT
• Downhole mud properties from sample
measurements
• Resistivities (RM, RMF, RMC)
Tsample 21.5
R fluidT2 R fluidSampl e 0
C
T2 21.5
• Salinities (SALM, SALMF)
3.562 logR75 0.0123
x
0.955
Salinity ppm @ 75 10 x
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Environmental Corrections
• Group of modules for the correction of raw wireline log data for the effects of
borehole conditions and mud weight.
• Based on digitized borehole correction charts or coded algorithms provided
by the wireline logging contractors.
• Most modern wireline tools produce logs with all corrections applied at the
time of logging (wells drilled after ~90’s).
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Analysis
Badhole
Coal
Volume of shale
Porosity
Water Saturation
Permeability
Mineral Volumes
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Identify bad hole conditions
• Based on the difference CALI – BS
• Creates four different type of flags:
OVERSIZE, RUGOSE,
OVER/RUG and GOOD
• The flags can be used as a logic
conditional on other modules.
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Identify coals
• Based on four different cutoffs related to:
density, neutron, slowness and resistivity
• The flag created outputs which cutoffs
were exceeded: D=density, N= neutron,
DT=slowness, R= resistivity
• It also can be used as a logic conditional
for other modules.
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Shale volume analysis
Selection of VSH Methods:
• Vsh from GR (if sandstone or carbonate is not radioactive)
• Vsh from density neutron (only if hole conditions are good and
there is no gas crossover and no dolomite)
• Vsh from SP (only if SP has sufficient character or resolution to
be believed)
• Vsh from sonic density crossplot (no secondary porosity)
• Vsh from minimum of above if there is no reason to prefer one
method over another
• Use linear methods unless local correlations have shown a need
for a non-linear
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Shale volume from GR
• The linear method uses the following equation:
VSH_GR = (GR - GR_MA) / (GR_SH - GR_MA)
• VSH_GR calculates three logs:
VSH_GR: volume of shale (larger than 1 if GR>GRVSH)
VSH: VSH_GR limited to be between 0 and 1
MTH_VSH: method used for VSH: Linear or Non-Linear
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Porosity analysis
Apparent
PHIA = ( RHO_MA - RHO )/(RHO_MA - RHO_FL )
True
PHIE = [( RHO_MA - RHO ) - VSH * ( RHO_MA - RHO_SH)]
/ ( RHO_MA - RHO_FL )
PHIT = PHIE + VSH*PHIT_SH
HC corrected*
DELTA_RHO = SHR * PHIE * A
A = 1.07 * ((1.11 - 0.15 * SALMF) * RHO_MF – (RHO_HC*(1.15 + 0.2*(0.9 -
RHO_HC)**2)))
* Note: HC corrected porosity calculation includes shale and hydrocarbon correction
based on the true density of the hydrocarbon, and its saturation in the flushed zone
(Gaymard and Poupon, 1967).
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Calculation of Porosity using
Density/Neutron Logs
DEN/NEUT
• Chart Lookup
• Bateman-Konen
• Assumptions:
1) the N calculated with respect to
limestone
2) formation fluid is water or oil but not
gas
• TOTAL
PHIT = PHIE + VSH * PHIT_SH
– PHIT_SH = ( RHO_DSH - RHO_SH)
/(RHO_DSH - RHO_W )
• When bad hole flagged, bad hole logic
allowed and sonic available, sonic is
used instead.
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Porosity Analysis
Selection of Porosity Methods:
• Density neutron crossplot (if hole is good and if both logs
are available).
• Sonic neutron crossplot in carbonates or in bad hole
where density is not acceptable.
• Density log corrected for shale (in good hole only).
• Sonic log corrected for shale (in bad hole or if nothing else
is available).
• Neutron log corrected for shale (in bad hole or if nothing
else is available).
Source: Crain’s Petrophysical Handbook
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Water Saturation Analysis
Water Saturation Relationships (Swe, Swt)
CW n
CT SW VSH CSH SW General form
F
Flushed and Unflushed Water Volumes
Voluwat Swe e
Vol xwat S xo e
Wet & Dry Shale Volumes
Voldryshale Vsh (1 TSH )
Volwetshale Vsh TSH
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Water Saturation Analysis
• Calculates water saturation using Archie’s
Law, based on total porosity.
• To allow general application when shale
volume is not zero, effective porosity must
be used as well.
• Equation assumes that the only conductive
material is water and will overestimate Sw
if the reservoir has clay-coated sand
grains.
• M can be constant or variable as selected
by OPT_M
• Note: Other models,
which consider
partial contribution
to the conductivity
due to the Vshale,
are also available
under the same
section.
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Permeability Calculation
• Calculates permeability from log data using Coates Free Fluid Index method.
• Note: Formation at Swirr when bulk volume water (BVW=Sw* ) values are
constant. BVW in the flushed and unflushed zones are displayed and
shaded as VOL_UWAT and VOL_XWAT , respectively within the porosity log
track, indicating the amount of movable hydrocarbon.
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Matrix Analysis
• TRUMAT estimates mineral volumes by calculating RHO_MAT, DT_MAT and U_MAT from the
following equations:
• RHO = PHIE * RHO_FL + (1 - PHIE - VSH) * RHO_MAT + VSH * RHO_SH
• DT = PHIE * DT_FL + (1 - PHIE - VSH) * DT_MAT + VSH * DT_SH
• U = PHIE * U_FL + (1 - PHIE - VSH) * U_MAT + VSH * U_SH
• Matrix analysis also possible by triangulation of
either the RHOma - Uma or RHOma – DTma
crossplots to solve for up to 3 mineral volumes
(Quartz, Limestone, Dolomite, Anhydrite)
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Estimate mineral content
• Allows ternary mineral distribution
of any 3 of Quartz, Calcite,
Anhydrite and Dolomite.
• Mineral proportions can also be
placed into a layout shaded
between VSH and PHI.
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