5.2 Dipmeter Imaging

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Advanced Formation Evaluation

October 2012

by Alain Brie

Dipmeters

Borehole Imaging Logs

5.2


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1 Advanced Formation EvaluationAlain Brie 2012

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

5.2 Dipmeter Imaging

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