08- Borehole Imaging
1
Oil Based Mud Imager Tools
Baker Hughes Schlumberger Weatherford Halliburton
Earth Imager OBMI OMI OMRI
6 independent calipers 4 calipers 6 independent calipers Oil Base Mud Imager Tool.
8 button pairs per pad 5 button pairs per pad 10 knives /pad 6 independent calipers.
120 samples per foot 120 samples per foot 8 measurements / pad 6 button pairs per pad.
400 samples per meter 400 samples per meter 120 samples per foot Unique pad design allows
30.7 ft Length 1” vertical resolution 400 samples per meter both vertical and horizontal
5.25 in. Diameter Rated @ 350 deg F Rated @ 350 deg F pad articulation for
25000 psi pressure
20,000 psi 20,000 psi increased formation contact.
Temp rating 350º F
120 samples per foot
1” vertical resolution
84 % borehole coverage in
6inhole
Rated @ 350 deg F & 20,000
psi
Borehole Imaging Fundamentals
Borehole Imaging Fundamentals
Borehole Image Data Display – 2D Presentation
Resistivity Traces of All Electrodes 2-D Presentation
pad 1 pad 2 pad 3 pad 4 pad 5 pad 6 pad 5 pad 6 pad 1 pad 2 pad 3 pad 4
higher
lighter
resistivity
colors
formation
tool navigation
data determines
the direction of
the pads
lower darker
resistivity colors
formation no
coverage
in gaps
between
N E S W N pads
resistivity increases
Borehole Imaging Fundamentals
Borehole Cross-Section
Depicts shape of hole at a particular depth •
Identifies reference pad azimuth (red pad) •
Identifies “low side” of hole azimuth (yellow line) •
Tabular data for hole azimuth, deviation, pad •
1azimuth, and depth
Useful in identifying stress directions•
Borehole Imaging Fundamentals
Static Image Versus Dynamic Image
Static • Static Dynamic Dynamic •
equalized equalized
images apply images apply
the color the color palette
palette over the over a short
entire logged display interval.
interval.
good to show •
good to show • image details
“relative”
values of Losing sense of •
resistivity relative
coloration
Losing image •
detail
Borehole Imaging Fundamentals
“In Hole” Dip Determination •
Distance from top of sinusoid (maxima) to •
bottom of sinusoid (minima) is the displacement.
Hole diameter values derived from caliper data •
* hole nearly vertical (from tool navigation)
displacemen
Dip mag = arc tan t
4
hole 1/2”
diameter
4.5”
Dip mag = arc tan
8” (from caliper)
Dip mag = 29 degrees
azimuth of sinusoid’s
minima determines dip
Borehole Imaging Fundamentals - Terminologies
Drift angle, Deviation or Inclination– angle of deviation of •
wellbore with respect to vertical
Drift azimuth or Hole Azimuth– direction of wellbore •
deviation with respect to north
Magnetic declination – value, in degrees, that magnetic •
north differs from true north for a specific location
Azimuth – horizontal angle distance from fixed reference •
direction to a particular position
Dip – quantity with a magnitude and direction •
Dip angle – angle between horizontal plane and bedding •
plane
Dip azimuth – direction the bedding plane dips down with •
respect to north
Borehole Imaging Fundamentals - Terminologies
Regional dip – inclination of •
sediments when average direction is
constant over wide area
Stratigraphic dip – related to •
orientation of strata at time of
deposition
Structural dip – inclination of •
sediments away from local sub-
surface high area
Structural Interpretation
I. Structural Dip Attitude Description & Structural Dip
Zonation.
II. Structural & Stratigraphic breaks Identification &
Characterization.
III. Fracture Identification & Characterization.
IV. Present Day Geostress Orientation Analysis.
Fault identification characterization
Image Identification – Snapshots
Facies juxtaposition across Large Scale (seismic) Fault with
Micro-displacement of bedding and
fault plane and bedding
lamination planes gouge & Breccia
termination
Fracture Identification & Characterization.
Natural Fracture Diagnosis- Conductive Open Fracture. .B
Natural open-fractures are induced with the drilling fluids during the drilling •
operation.
If the drilling fluids are water based mud then fracture will be filled with a •
conductive medium and easily detected among the resistive background.
If the drilling fluids are oil based mud then other tools have to be integrated to get •
more information about the fracture type.
Present Day Geostress Orientation Analysis
Dynamic Image Logs
• Geologic Structures Reflect Either Past or
Current Stress Fields (or Both);
Induced
Fracture
• The propagation of Induced fractures
relative to the breakout.
• Induced fractures extends in direction
parallel to maximum horizontal stress.
• Breakout extends normal to the induced
fractures in a direction parallel to minimum
horizontal stress. Natural
Breakout Fracture
World Geostresses Map
Vuggy Zone Identification and Characterization
Vugs often begin as •
fractures and become
increasing widened through
dissolution
Fossilized remains or •
bioturbated sediment may
be selectively dissolved.
May become “moldic” type •
porosity, thus lacking
significant interconnectivity
Resistive Vuggy Patches
Vuggy disseminated Spots
Single Well Sedimentological & Stratigraphic
Analysis.
I. Electro-Facies Identification (core Integration/calibration if
available).
II. Facies association
III. Depositional modeling.
IV. Paleocurrent flow analysis.
2) Single Well Sedimentological & Stratigraphic
Analysis.
II. Facies association Analysis & depositional Modelling
Laminated Reservoir (Thin bed reservoir
analysis)
Laminated Reservoir (Thin bed reservoir
analysis)
