Resistivity Logs.ppt

1 FE – OverviewFarag July 2002

Resistivity Logging

Resistivity LogResistivity Log

• Basics about the Resistivity:

• Resistivity measures the electric properties of the formation,• Resistivity is measured as, R in W per m,• Resistivity is the inverse of conductivity,• The ability to conduct electric current depends upon:

• The Volume of water, • The Temperature of the formation,• The Salinity of the formation

The Resistivity Log: Resistivity logs measure the ability of rocks toconduct electrical current and are scaled in units of ohm-meters.The Usage: Resistivity logs are electric logs which are used to:

Determine Hydrocarbon versus Water-bearing zones, Indicate Permeable zones, Determine Resisitivity Porosity.

Resistivity

• Resistivity is the opposition to flow of electrical current offered by a material of unit length and unit cross sectional area. It is a property of the material itself, not of its shape or dimensions.

Unit length, L

Current, I

Voltage, V

Unit area, A

Resistance and Resistivity

• Ohms Law: V = I R

• Resistance, R = r (L / A)

• Therefore V = I r (L / A)

• So r = (V / I) (A / L)

• Let k = A / L (Geometric Factor)

• So, r = (V / I) k

Conductance and Conductivity

• Conductance is the reciprocal of resistance. It represents the ease with which current flows through a given circuit.

• Conductivity is the reciprocal of resistivity. It represents the ease with which current flows through a certain material. It is a property of the material itself.

• Resistance unit: ohm (Ω)• Resistivity unit: ohm-meter (Ω·m2/m, or Ω ·m)• Conductance unit : siemens or mho • Conductivity unit: siemens/meter or mho/meter.

Resistivity Logging

There are two types of resistivity logging tools:

• Laterolog tools send a current from electrodes on the logging tool, through the formation, to a return electrode located either at surface or downhole.– Laterolog tools need a conductive path between the logging tool

and the formation

• Induction tools generate current loops in the formation and measure the strength of the electromagnetic signal created by these current loops. – Induction tools do not require a conductive path in the borehole.

They work in oil-base muds and air-filled holes.

Basic Resistivity tool types

Induction Logging ToolsLaterolog Logging Tools

Logging ToolBorehole

Uninvaded Zone

Invaded Zone

Laterolog vs. Induction Current Path

Laterolog Response

Induction Response

Resistivity

There are two main techniques for measuring resistivity:

Laterolog : Current is injected into the formation

Induction : Current loops are induced in the formation

LatrologsPEx-HALS

Resistivity : Laterolog

Current is forced through the mud into the formation

Dual Laterolog Measurement

LLD: deep measurement, currect returns to surface.

LLS: shallow measurement, current returns to the tool itself.

Bucking Current

Measure Current

280 HzCurrentSource

MonitoringLoop

Resistivity : Laterolog Shallow (LLS)

Bucking Current

Measure Current

35 Hz Aux Mon.

MonitoringLoop

Bucking Current

FishLCM Module

35 Hz Current

Resistivity : Laterolog Deep (LLD)

Resistivity : Laterolog invasion effects

RLL = Vm Rm + Vmc Rmc + Vxo Rxo + (1-Vm-Vmc-Vxo) Rt

Resistivity : Laterolog

Ra = VRm(Rm) + VRmc(Rmc) + Vrxo(Rxo) + VRt(Rt)

If Rmf < Rw then Rxo < LLS < LLD < RtIf Rmf > Rw then Rxo > LLS > LLD > Rt

Using Rxo, LLS & LLD, Rt and Di can be computed

Resistivity : Laterolog azimuthal measurements

LatrologsEnvironmental corrections

Groningen Effect

• Caused by highly resistive beds overlying the formation that is being measured.

• This forces the deep current into the mud column.

• This is caused by the voltage reference (cable-torpedo) becoming non-zero.

• LLd reads too high• More pronounced at low resistivity

Borehole & Invasion Effects

Ra = Vm*Rm + Vxo*Rxo + Vt*Rt

Resistivities measured in series

Invasion Enhances Shoulder Effects

Shoulder-Bed Squeeze Effects

Deep measurement reads too high and results in erroneous invasion

profile.

All resistivities read lower than Rt and separation is reduced.

Platform Express HRL FMI

LatrologsHRLA (High Resolution Array Laterolog)

HRLA Solutions Hardware

Mode 1 Mode 2 Mode 3

Mode 4 Mode 5

Multiple depth of investigation• Clear indication of invasion• Improved vertical resolution• No need for deep mode or bridle• No Groningen or drillpipe-

conveyed logging effects and reduced shoulder-bed effect

HRLA 1D Real-time Answer

Real-time wellsite product gives clear answers for quick decisions:

- Eliminates voltage reference effects

- Less shoulder-bed effect

- Self consistent depth matched measurements

Answer Benefits: Reduced Shoulder-bed Effect

HRLA tool HALS tool 1D-Rt comparison

1D radial model

(invasion)thick-bed

approximation

Answer Benefits: No Groningen Effect

Curve separation suggests

invasion but is due to

Groningen effect

HRLA resistivities clearly show zone is not invaded

Answer Benefits: Thin-Bed and Invasion Profiling

Curve separationshows invasion

High verticalresolution

Curve separation results from Groningen effect

Groningen effectin indicator curve

HRLA tool DLL tool

HALS - standard and hires

HALS LQC

Groningen flag

LQC - Out of limits (example)

HIGH RESISTIVITY BED

HALS - out of limits

HIGH RESISTIVITY BED

HALS NoisePrimarily from Rig Generator

Rig Generator OFF Rig Generator ON

InductionsAIT

AIT-H Stand-Off Positioning

Resistivity : Induction

Operating Range

• 0.1 to 2000 ohmm• Moderate Rxo < Rt• Rt/Rm <100 (with hole diameter

considered)• Large diameter holes with moderate Rt/Rm

and moderate Rt

Induction response errors

• Skin effect & Mutual Inductance• Borehole effect• Cave effect• Shoulder effect• Invasion effects

1/Ra = 1/(VRm(Rm)) + 1/(VRmc(Rmc)) + 1/(Vrxo(Rxo)) + 1/(VRt(Rt))

If Rmf < Rw, AT10 < 20 < 30 < 60 < 90If Rmf > Rw, AT10 > 20 > 30 > 60 > 90

From the 5 curves Rt can be computed

Resistivity : InductionFocusing

Resistivity : InductionHole size and shapeUncertainty in hole size or mud resistivity can cause large errors on the shallow curves but much smaller errors on the deeper measurements

Out of sequence

Resistivity : InductionInvasion

Very deep invasion can affect even the deepest measurements, non-cylindrical invasion may affect the Rt computation

Induction Resistivity in Deviated Wells

Relative dip angle

Shallow Resistivity Deep Resistivity

low relativedip angle

high relativedip angle

Inductions vs Laterologs

Comparison to AIT

BS = 8”

Rt = 200

Rxo = 30

Rm = 0.1

S/O = 1.5”

BS=8.5Rm=0.5Rxo=5.0Rt=200

Resistivity : Tool planner

BS=12Rm=0.5Rxo=5.0Rt=200

BS=12Rm=1Rxo=5.0Rt=200

Resistivity Logs.ppt

Documents

Transcript of Resistivity Logs.ppt

Resistivity Surveying OhmMapper Capacitively Coupled Resistivity System (CCR)

Introduction to Resistivity Logging. Outline Definitions and Uses Resistivity in Rocks Archie’s Equations Invasion and Invasion Models Measuring Resistivity.

Resistivity Log

Soil Resistivity and GroundingSoil Resistivity and ... - · PDF fileSoil Resistivity and GroundingSoil Resistivity and Grounding Systems Testing Roy “Chip” Whitten Senior Applications

Resistivity Imaging

Resistivity Logging.pptx

Resistivity & Circuits

Applications of Integrated Vessel-based LiDAR, Multibeam ... · Marine Survey Methods Continuous Resistivity Profiling (CRP) Marine Geophysical Methods - Resistivity N Resistivity

(i)._Introduction to the resistivity surveying method. The resistivity of

Si Resistivity Reference Wafer : NRW Series...The Pioneer for Sheet resistance/Resistivity measurement A global leading company for resistivity measurement system. Si Resistivity Reference

DC Resistivity · 2017-09-07 · DC resistivity surveys and data n Inject current. n Measure potentials. n Potentials depend upon the distribution of subsurface resistivity. n Resistivity

Electrical Methods Resistivity Surveyingmarshallst/GLY3160/lectures/12_Resistivity.pdf · Geologic Resistivity 101 • Resistivity surveying investigates variations of electrical

Resistivity Results

Thermal Resistivity

ARS RESISTIVITY SCANNER USER MANUAL · 3.2 RESISTIVITY The Resistivity Menu is seen on the LCD screen when the system turned on. Resistivity menu is as follows: AUTO SCAN: Automatic

Soil Resistivity • Ground Resistance • 3-Point · PDF file• Soil Resistivity • Ground Resistance • 3-Point Measurements ... Soil Resistivity Measurements ... After inspection,

Peta Resistivity

Section10 resistivity

Resistivity Modeling

Advances in Micromodeling using Resistivity Borehole Images Website... · Advances in Micromodeling using Resistivity Borehole Images ... Resistivity borehole images offer a high