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Resistivity Logging

Resistivity

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Resistivity Logging

Objectives : Electrical Surveys Normal Lateral

Induction Logging transformer principle

conductivity measurementLaterolog Tools sharply focused current beam

resistivity measurement

Choice of Induction vs. LaterologMicroresistivity Surveys

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Resistivity Logging

Why Resistivity ???

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Resistivity Logging

Why Resistivity ?

because Electrical Resistivity is themost sensitive parameter to

distinguish between salt water and

hydrocarbons

salt water: fair conductor oil (or gas): insulator

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Resistivity Logging

Surface Electrical Prospecting

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Resistivity Logging

Well Logging

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Resistivity Logging

Old Electrical Logs

Normals

Laterals

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Resistivity Logging

Normal device N Lateral device

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Resistivity Logging

Normal Electrode Arrangement

A M N

Lateral Electrode Arrangement

A M N

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Resistivity Logging

Response of

NORMAL

device

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Resistivity Logging

Response of NORMAL device

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Resistivity Logging

Response ofLATERAL

device

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Resistivity Logging

Response of LATERAL device

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Resistivity Logging

Limitations ofNormal and Lateral devices

Current leakage along the borehole

Need focused devices

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Resistivity Logging

Electrical Resistivity

Induction Method

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Resistivity Logging

Induction System

double transformer

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Resistivity Logging

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Resistivity Logging

Induction : double transformer

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Resistivity Logging

Induction : Loop around borehole

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Resistivity Logging

Induction Logging

6 FF 40

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Resistivity Logging

Induction Logging

6 FF 40 coil array

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Resistivity Logging

Principle of Induction Log

electromagnetic field induces concentriccurrent loops

reads conductances in parallel

c IL = cm + cmc + cxo + c t

c = 1 / r

works best when rm + rmc + rxo are large

compared to rt

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Resistivity Logging

Induction Log works best in . . .

low resistivity or high conductivity formations

low Rt and high Rxo

low resistivity zone between high resistivity beds

oil based mud

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Resistivity Logging

Induction: Radial Focusing

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Resistivity Logging

Induction: Vertical Focusing

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Resistivity Logging

Depth of Investigation

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Resistivity Logging

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Resistivity Logging

6FF40 InductionInvestigation Geometry

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Resistivity Logging

Dual

InductionLog

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Resistivity Logging

Induction Log : Summary

tool emits electromagnetic waves

eddy currents flow in a loop around the hole

measures conductivity

ideal for Rt in a water zone

works in oil-based mud

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Resistivity Logging

Electrical Resistivity

Laterolog Method

Guard or Spherical

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Resistivity Logging

Laterolog System

uses multiple electrodes

to monitor and focus current

generates sharply focused

current beam

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Resistivity Logging

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Resistivity Logging

Laterolog Systems

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Resistivity Logging

Laterolog 7 Focusing

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Resistivity Logging

Dual Laterolog

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Resistivity Logging

Principle of Laterolog

focused current sheetreads resistances radially in series

rLL = rm + rmc + rxo + rt

works best when rm + rmc + rxo

are small compared to rt

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Resistivity Logging

Laterolog works best in . . .

high resistivity formations

high Rt and low Rxo

high resistivity zone between low

resistivity beds

salt mud

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Resistivity Logging

Laterolog : Summary

tool emits current

monitors current leakage and adjusts focusing

measures resistivity

ideal for Rt in oil zone or high resistivity

suited to salt mud

Spherically

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Resistivity Logging

Spherically

FocusedLog

SFL

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Resistivity Logging

Choice of Type of Measurement

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Resistivity Logging

Laterolog vs. Induction

Vertical Resolution

Laterolog very sharp . . .3

Induction poor . . .7 without enhancement

similar depths of investigation

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Resistivity Logging

Resistivity or Conductivity

Resistivity Tools: E = IRL /Ahold I constant

measure E proportional to R

Conductivity Tools: I = CEA / L

hold E constant

measure I proportional to C

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Resistivity Logging

Microresistivity Logs

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Resistivity Logging

Microlog

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

Microlog vs. Microlaterolog

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Resistivity Logging

Microspherically Focused Log MSFL

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Resistivity Logging

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Resistivity Logging

New Induction Tools

Phasor Processing of 6 FF 40 Signal

3 frequencies

complex sharpening filter

Array Induction (AIT)

multiple transmitter receiver sets

28 signals 5 depths of investigation

3D Explorer

3 orthogonal measurements, X,Y,Z

2 oriented conductivities, H,V

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Resistivity Logging

PhasorProcessing

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

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Resistivity Logging

3-D Explorer

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Resistivity Logging

AzimuthalLaterolog

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Resistivity Logging

ARI