GEOPHYSICAL LOGGING FOR Ground Water

• Introduction • Field Operations • Methods• Log Analysis• Conclusion

INTRODUCTION

• Pioneered by for O&G • Making record of subsurface physical

properties to characterize geology • Also known as down-hole(DH);borehole;

well ;wireline logging(O&G)

WHY LOG?

• To assist in hydro-geological assessment; samples aren’t depth corrected

• To calibrate formation resistivity from GG• To assist in well design • To QC drilling contractor’s work for claims

purpose: diameter, casing/screen installed etc.

FIELD OPERATIONS

• Lowering tool into well using cable attached to auto-winch connected to laptop via hardware and powered by 12V DC

• Refer to Borehole logging – How To @ \\172.16.26.2\Technical Data\Perak\50MLd Groundwater Project in Btg Pdg\Downhole_ Geophysics\NOTES

SCHEMATIC

On Golf Cart@KLGCC

Carried-out Winch @Cluny

In-vehicle winch @Bedford

Under the sun @K. Slim

In the Rain @Cluny East

METHODS

• TCDS/TCGS incl. temp, conductivity ( + gamma)

• ELOG incl. resistivity & natural gamma• CALP – well diameter• SIND – conductivity (calc. resistivity) + gamma• OPTV – Optical televiewer• FLOW – Impeller Flowmeter

1a.TCDS/TCGS

• TCDS/TCGS – Temp, conductivity (+ Gamma)• Thermister measures fluid temperature(deg.

Celsius).• Applied in porous & fractured acquifers• Detects influx/efflux; Logging speed 3m/min• Drilling mud/fluid affect readings

1b.CONDUCTIVITY

• Unit – Siemens• Conductivity = 1/resistivity(Ohmm)• Application in porous acquifers; high-salty• Most well in SEL being relog by SIND tool for

confirmation

TCGS SONDE LAYOUT

• Sample log with temp gradient…..SL290 w/• CALP

TEMPERATURE PROFILE

TEMPERATURE

DEPT

H

SURFACE

CONDUCTIVE GRADIENT

HYDROTHERMAL SYSTEM

UPFLOW

CONDUCTIVE HEAT SOURCE

OUTFLOW ZONE

TEMPERATUREREVERSAL

2.ELOG

• ELOG – Resistivity: short, long,SPR ,SP & natural Gamma

• Applied in porous & fractured acquifers both• Sand/gravel give high readings in resistivity;

low in gamma• Clay & shale give low readings in resistivity;

high in gamma

RESISTIVITY DEPENDS ON

• Porosity &Water content• Water Chemistry • Rock chemistry ; Quartz - high; Clay - low • Degree of rock alteration & mineralization• Temperature

ELOG SONDE LAYOUT

LON

• Sample log with …..SL290

3.CALP

• CALP – measures well diameter• Detects fractures & installed casing.• Applied in fractured acquifers• Logging speed 5m/min; uphole run only• Caliper needs to open completely or incorrect

readings

CALP SONDE LAYOUT

4.SIND

• SIND – Inductive conductivity (EM:Tx/Rx)• Measures conductivity(calc. resistivity)• Applied in porous acquifers (alluvium)• Detects salinity (from cond.); Logging speed

5m/min• Drilling mud/fluid affect readings

SIND SONDE LAYOUT

1. KLT026 (~97m)Raw data as logged on 11/1/2010

Slide 6: SIND Data Slide 7: ELOG Data

Depth: 45m-51mAnomaly observed between 47-50m on resistivity and gamma readings.

FLOW-METER@SPINNER LOG

• Propeller measures flow in well• Identifies depth of water in-flow• Calculate fluid velocity from series of up and

down runs at different cable speeds

Flow-meter

LEDElliptical lens

Protective PVC tape