dlt1 wireline and testing etc 10/27/2015 introduction to laterolog principles

DLT1

Wireline and Testing

ETC 04/21/23

Introduction to

Laterolog

Principles

DLT2


ETC 04/21/23

Outline

• Introduction

• Physics of Measurement– Resistivity Model– Laterolog Model

– FOCUSSING - Passive, Active,

– Equipotential

• DLT Physics

– Electrode Configuration

– Shallow Laterolog

– Deep Laterolog, LCM, 35 Hz

– Voltage Measurements , Bridle,

– Dynamic Power Tool

• Groningen – Groningen Effect– Groningen Detection

DLT3


ETC 04/21/23

Formation Model - Recap

• Objective is to get Rt

• Rmud and Rxo can affect Rt measurement

DLT4


ETC 04/21/23

Resistivity Why - Recap

GOAL ---- > HYDROCARBON

Rt , Rw, and needed to determine Sw from Archie’s equation

Invasion occurs due to drilling process

Rt Measurement is affected

To estimate Rt, measurements in :Deep/Virgin ZoneTransition ZoneFlushed Zone

DLT5


ETC 04/21/23

Need for DLT

AIT is not suitable for all environments

When Borehole fluid very conductive --- Resistivity better suited than Conductivity

LATEROLOG -- Two measurements

Deep Resisitivity (LLD) can see in virgin zone

Shallow Resistivity (LLS) can see transition zone

DLT6


ETC 04/21/23

Resistivity Measurement - Model 1

DLT7


ETC 04/21/23

Resistivity Measurement - Model 2

DLT8


ETC 04/21/23

Laterolog - Ideal Model

I0

V= V0

V= 0

L

r

• Current lines parallel and radially outwards

• Represents tool in a borehole

• Io = Total Current V = V0=V

• Resistivity = K V0/I0

• K = Geometrical Factor --- Cylinder

• DLT achieves 90 % of the theoretical model

DLT9


ETC 04/21/23

Equipotential

• Equipotential Lines = Same Potential along a line

• Current can flow only perpendicular to Equipotential

• Current <--> Equipotential : Related and Affects each other

• By controlling Equipotential we can control Current flow– If equipotential line parallel to hole then current goes into the formation and along mud

column. This will be used in DLT design.

DLT10


ETC 04/21/23

Laterolog - Focussing

• Simple electrode geometry is inadequate

• Current finds the easiest path

• Current may go through borehole

• So FOCUSSING of current is necessary

V

DLT11


ETC 04/21/23

Passive Focussing

• The Bucking Current constrains/focusses the Measure Current

• Note distortion of Equipotential line

• Can cause currents in borehole (unwanted)

DLT12


ETC 04/21/23

Focussing - Active

• Note Monitoring Electrodes are introduced

• The Bucking Current is adjusted to have Vm1 - Vm2

• Note Equipotential line shape near A0 electrode.

DLT13


ETC 04/21/23

Focussing - Computed

Achieves Focussing through Mathematical Superposition of Currents and Voltages

Electromagnetic waves - Superpostion Principle is aplicable

To be discussed later ....

HALS / ARI use these principles

DLT14


ETC 04/21/23

Laterolog Principle - LLS (Shallow)

Bucking Current

Measure Current

A2

A1

M2

M1

A0

280 HzCurrentSource

MonitoringLoop

CURRENT PATHS

• Measure Current is sent from A0 and returns to A2

• Bucking Current is sent from A1 and returns to A2

• 280 Hz current is generated downhole inside tool

MAIN MONITORING LOOP

• Voltage between M1 and M2 is monitored

• Measure Current is adjusted to Keep VM1-VM2 =0

DLT15


ETC 04/21/23

Laterolog Principle - LLD (Deep)

Bucking Current

Measure Current

A2

A1

M2

M1

A0

A1*

35 Hz Aux Mon.

Loop

MonitoringLoop

Bucking Current

Fish

LCM Module

35 Hz Current

DLT16


ETC 04/21/23

Laterolog Deep - Principles

CURRENT PATHS

• 35 Hz laterolog current is generated at surface - LCM

• Measure Current sent from A0 and returns to Surface “Fish”

• Bucking Current is sent from A1 and A2

• Bucking Current returns to Surface “Fish”

MAIN MONITORING LOOP

• Voltage between M1 and M2 is monitored

• Measure Current is adjusted to Keep VM1-VM2 =0

AUXILLARY MONITORING LOOP

• A1 and A2 needs to be kept at same potential for 35 Hz only

• Voltage between A1* and A2 is monitored

• Bucking current distribution altered to keep VA2-VA1* =0

• Current density is high at A1

• Hence potential is measured at A1* which is very close

DLT17


ETC 04/21/23

Laterolog - Depth of Investigation

280 Hz35 Hz

Both LLD and LLS are measured simulataneouslyLLD = 35 Hz LLS = 280 Hz

LLS Depth of Investigation Approximately - 2 feet *

LLD Depth of Investigation Approximately - 10 feet *

* Depends on formation resistivity

DLT18


ETC 04/21/23

DLT Measurement - Simplified

Surface Electrode

Measure I0

Measure V0

Torpedo

Bridle

A2

A0

A2

Outer Equipotential measured at Torpedo

Inner Equipotential measured at M2 electrode

M2

Mass

Mass

LLS LLD

Cable

Voltage is measured between M2 and Armor for LLS and LLD

DLT19


ETC 04/21/23

Constant Voltage & Current Devices

I (Measured) = V/r = K x C x V

Constant voltage is appliedCurrent varies with ConductivityCurrent is measuredExamples - SFL, MSFL

LimitationIf R is very high, C is very low I is too low to measured

Constant Voltage Device

V(Measured) = I x r = K x R x I

Constant current is appliedVoltage varies with resistivityVoltage is measuredExamples - Old Normal and Lateral Devices

LimitationIf R is very low, V is too low to measureI is too low to measured

Constant Current Device

Both these devices have limitation in DYNAMIC RANGE

DLT20


ETC 04/21/23

Laterolog - Dynamic Range

Log R

Log P

RL = 68 mRLow Rhigh

Pmax = 4800 nw

Pmin = 500nw

Laterolog Devices vary both Current and Voltage

Dynamic Range of measurement increases

POWER sent by tool depends on measured resistivity

Power control is done uphole

DLT21


ETC 04/21/23

Laterolog - BRIDLE

Cable Armor # 10 is electrically insulated from EQCS body

Electrode V is for SP MeasurementElectrode VI is for Groningen Voltage Measurement

18 ft 62 ft

11 ft

80 ft

EQCS1 ft 1 ftVI V

1234567

10

89

ARMOR (Internal)

Spare Conductor

VI

V

1234567

10

Cable Torpedo Bridle Head

Weak Point

DLT22


ETC 04/21/23

Laterolog - Groningen Effect

High Resistivity Bed

Deep Current


• Presence of High Resistivity Bed causes Deep current to flow through the mud

• This affects the Voltage Reference at Torpedo

• Shallow current returns to A2 - hence no effect.

DLT23


ETC 04/21/23

Groningen Effect - Detection


18 ft

18 ft

18 ft

LLD

LLG

Resistivity

V gron

Vo

• Vg is measured between Groningen Electrode (bridle) and M2

• LLG uses Vg as voltage instead of V0

• Groningen Effect can be detected from LLD and LLGseparation

• LLS is unaffected

DLT24


ETC 04/21/23

DLT - Log Example

SHALE - Impermeable Zone

Sandstone - Permeable Zone

SHALE - Impermeable Zone

DLT25


ETC 04/21/23

LQC - LLG and LLD

LLG = LLDwhen no Groningen Effect

dlt1 wireline and testing etc 10/27/2015 introduction to laterolog principles

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