DLT1 Wireline and Testing ETC 10/27/2015 Introduction to Laterolog Principles

DLT2 Wireline and Testing ETC 10/27/2015 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 Wireline and Testing ETC 10/27/2015 Formation Model - Recap Objective is to get Rt R mud and R xo can affect Rt measurement

DLT4 Wireline and Testing ETC 10/27/2015 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 Zone Transition Zone Flushed Zone

DLT5 Wireline and Testing ETC 10/27/2015 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 Wireline and Testing ETC 10/27/2015 Resistivity Measurement - Model 1

DLT7 Wireline and Testing ETC 10/27/2015 Resistivity Measurement - Model 2

DLT8 Wireline and Testing ETC 10/27/2015 Laterolog - Ideal Model I0I0 V= V 0 V  = 0 L r Current lines parallel and radially outwards Represents tool in a borehole Io = Total Current  V = V 0 =V  Resistivity = K V 0 /I 0 K = Geometrical Factor --- Cylinder DLT achieves 90 % of the theoretical model

DLT9 Wireline and Testing ETC 10/27/2015 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 Wireline and Testing ETC 10/27/2015 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 Wireline and Testing ETC 10/27/2015 Passive Focussing The Bucking Current constrains/focusses the Measure Current Note distortion of Equipotential line Can cause currents in borehole (unwanted)

DLT12 Wireline and Testing ETC 10/27/2015 Focussing - Active Note Monitoring Electrodes are introduced The Bucking Current is adjusted to have Vm1 - Vm2 Note Equipotential line shape near A0 electrode.

DLT13 Wireline and Testing ETC 10/27/2015 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 Wireline and Testing ETC 10/27/2015 Laterolog Principle - LLS (Shallow) Bucking Current Measure Current A2 A1 M2 M1 A0 280 Hz Current Source Monitoring Loop CURRENT PATHS Measure Current is sent from A 0 and returns to A 2 Bucking Current is sent from A 1 and returns to A Hz current is generated downhole inside tool MAIN MONITORING LOOP Voltage between M1 and M2 is monitored Measure Current is adjusted to Keep V M1 -V M2 =0

DLT15 Wireline and Testing ETC 10/27/2015 Laterolog Principle - LLD (Deep) Bucking Current Measure Current A2 A1 M2 M1 A0 A1* 35 Hz Aux Mon. Loop Monitoring Loop Bucking Current Fish LCM Module 35 Hz Current

DLT16 Wireline and Testing ETC 10/27/2015 Laterolog Deep - Principles CURRENT PATHS 35 Hz laterolog current is generated at surface - LCM Measure Current sent from A 0 and returns to Surface “Fish” Bucking Current is sent from A 1 and A2 Bucking Current returns to Surface “Fish” MAIN MONITORING LOOP Voltage between M1 and M2 is monitored Measure Current is adjusted to Keep V M1 -V M2 =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 V A2 -V A1* =0 Current density is high at A1 Hence potential is measured at A1* which is very close

DLT17 Wireline and Testing ETC 10/27/2015 Laterolog - Depth of Investigation 280 Hz35 Hz Both LLD and LLS are measured simulataneously LLD = 35 HzLLS = 280 Hz LLS Depth of Investigation Approximately - 2 feet * LLD Depth of Investigation Approximately - 10 feet * * Depends on formation resistivity

DLT18 Wireline and Testing ETC 10/27/2015 DLT Measurement - Simplified Surface Electrode Measure I 0 Measure V 0 Torpedo Bridle A2A2 A0A0 A2A2 Outer Equipotential measured at Torpedo Inner Equipotential measured at M2 electrode M2M2 Mass LLSLLD Cable Voltage is measured between M2 and Armor for LLS and LLD

DLT19 Wireline and Testing ETC 10/27/2015 Constant Voltage & Current Devices I (Measured) = V/r = K x C x V Constant voltage is applied Current varies with Conductivity Current is measured Examples - SFL, MSFL Limitation If 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 applied Voltage varies with resistivity Voltage is measured Examples - Old Normal and Lateral Devices Limitation If R is very low, V is too low to measure I is too low to measured Constant Current Device Both these devices have limitation in DYNAMIC RANGE

DLT20 Wireline and Testing ETC 10/27/2015 Laterolog - Dynamic Range Log R Log P R L = 68  m R Low R high P max = 4800 nw P min = 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 Wireline and Testing ETC 10/27/2015 Laterolog - BRIDLE Cable Armor # 10 is electrically insulated from EQCS body Electrode V is for SP Measurement Electrode VI is for Groningen Voltage Measurement 18 ft62 ft 11 ft 80 ft EQCS 1 ft VI V ARMOR (Internal) Spare Conductor VI V CableTorpedoBridleHead Weak Point

DLT22 Wireline and Testing ETC 10/27/2015 Laterolog - Groningen Effect High Resistivity Bed Deep Current High Resistivity Bed 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 Wireline and Testing ETC 10/27/2015 Groningen Effect - Detection High Resistivity Bed 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 Wireline and Testing ETC 10/27/2015 DLT - Log Example SHALE - Impermeable Zone Sandstone - Permeable Zone SHALE - Impermeable Zone

DLT25 Wireline and Testing ETC 10/27/2015 LQC - LLG and LLD LLG = LLD when no Groningen Effect