A d v anced Form at ion Evalu at ion October 2012 by Alain Brie Dipmeters Borehole Imaging Logs 5.2
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Advanced Formation Evaluation
October 2012
by Alain Brie
Dipmeters
Borehole Imaging Logs
5.2
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Geology Oriented Log Measurements
Inclination of layers provide information of the formation structureand faults.
Bedding within layers, or stratigraphy, inform about the deposition
history.
Dipmeters are tools designed to provide inclination and bedding.
Geologists want more detail images of the rock structure at a fine
scale as if they were looking at a core.
Imaging tools based either on resistivity, induction or ultrasonic
techniques provide this information.
They also tell about fractures and borehole deformation.
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Stratigraphic High Resolution DipmeterTool (SHDT with 4-
pads and 8 buttons).
Dipmeter Logs
4 pads are applied against
the bore hole wall. One or two button electrodes
on each pad record the
resistivity of the layers.
Resistivity curves arecorrelated to obtain formation
dips.
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Correlation principle
0 10 20 30 60 90
Dip magnitude
Dip azimuth
Dipmeter Log Presentation
Tadpole orientation
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Apparent Dip and True Dip
ApparentDip
Plane ofElectrodes
Horizontal
True Dip
Vertical
Hole Deviation
ApparentDip
Plane ofElectrodes
Horizontal
True Dip
Vertical
Hole Deviation
Dips calculated are with respect to the tool and the well, i.e., apparent.
They are then corrected for well deviation to obtain true dip.
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Stratigraphic Dipmeter Interpretation
Stratigraphic interpretation tells
the geologist about thesedimentary environment.
Here we are in a deltaic
environment with river channels
and bars.
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Dipmeter Interpretation - Dip Patterns
Blue Pattern:
Increasing upwards
Constant azimuth
Green Pattern- Structural Dip:Constant dip
Constant azimuth
Red Pattern:
Decreasing upwards
Constant azimuth
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Stratigraphic Dip Evaluation Example of a Channel
The geologist can identify the different channels
and even the current direction from the dip
patterns.
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Structural Dip 20E
Structural Dip Removal
OriginalStructural Dip
Removed
Removing structural dip brings up bedding features and
helps interpretation
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Unconformity Dip motif
Angular unconformity
Angular unconformity in Algeria
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Fault Dipmeter Motifs
Normal fault with drag on upper block Reverse fault with drag on both blocks
Normal fault Reverse fault
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Examples of Faults Patterns on Dipmeter
Growth faultNormal fault with dragReverse fault with drag
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Thrust Fault
Thrust fault with beds overturned by
drag in upper block
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From Dipmeter to Imaging Tools
19451945
PresentPresent
3Sensors
62Sensors
4Sensors
64Sensors
192Sensors
8Sensors
PDT HDT SHDT
FMIFMS
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4 Arms - 8 Pads
192 Electro des
The FMI has 4 pads and
4 flaps to cover 85% of an
8 in borehole.
Each pad and flap
features 24 buttons in tworows giving a total of 192
buttons.
FMI Formation Micro-Imager Tool
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Compared SHDT and FMI Coverage
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E
N W
S
Images Viewed Inside Out
E
N
WS
N
EN WS N
0 90 180 270 360
E
N W
S
N E S W N
Good S i ne W a v e F i t t h r ough A l l P o in t s
P la n e r C o n ac
N E S W N
Poo r S ine Wave F i t through Al l Points
N o n - P l a n e r C o n ta c t
Images Viewed Inside Out
Borehole Image Presentation
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Dips calculated from FMI Images
Dips are calculated and visualizedon the FMI image.
An interactive program allows
selection and editing.
Fractures are identified andevaluated.
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Major Normal Fault
GR Caliper RHOB Structural FMI interpreted FMI static FMI LLD/LLS+ drift - APLC interpretation dip results image litho + MSFL
Dragging effect produced by a
major fault
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Example-1: Healed / Mineralized Fractures in Core & FMI Images in a vertical well.
The tadpole plot gives the angle and direction of the fractures
Natural FractureNatural Fracture
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Induced Fractures Strike
Borehole Breakouts Strike
1
3
ENE-W
SW
NNW-SSE
Borehole Breakout & Drilling Induced FracturesBorehole Breakout & Drilling Induced Fractures
Oil B M dDi t dB h l I T l
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Oil-Base Mud Dipmeter and Borehole Imager Tools
Resistivity based devices, hence
HDT, SHDT and FMI, cannot work inOBM.
Specific tools using micro-induction
technology were developed for
OBM: OBDT, and OBMI.
The OBMI Tool has 4 pads and 10micro-induction buttons per pad,
hence a total of 40 buttons.
Ultrasonic scanners can also be
used: BHTV or UBI (ultrasonic
Borehole Imager)OBDT
Oil-Base Mud Dipmeter
Tool
OBMI Pad
Oil-Base Mud
Micro-Imager Tool
Oil B M dB h l I
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UBIAmp lit ude
Dynamic
OBMIDynamic
UBITransit Time
Dynamic
Oil-Base Mud Borehole Images
Depth
m
Oth D i ithDi d I i C biliti
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Other Devices with Dip and Imaging Capabilities
Azimuthal Laterologs: ARI and HALShave 12 azimuthal measurement
electrodes giving a low resolution image
of the formation.
Ultrasonic scanners: BHTV or UBI
(ultrasonic Borehole Imager) have a
rotating ultrasonic sensor.
HALSAzimuthal Laterolog
Sonde
LWDB h l I i ithRABT l
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LWD Borehole Imaging with RAB Tool
The RAB Tool generates borehole images from 3 resistivity
buttons. Resistivity is scanned 56 times per rotation.
Structural dip is evaluated.3 azimuthal
electrodes
RAB / GVR Tool
RABImagingofBoreholeBreakoutsandFractures
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RAB Imaging of Borehole Breakouts and Fractures
Breakouts
Drilling inducedfractures
Tensile
Fracture Compressive
Failure (shear)Pmud
min
Max
BreakoutInduced
Fracture