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Slim-Hole Induction Tool (SIND):Field Evaluation @ Batu Dam, Gombak
May 11th 2010
Contents
• Introduction
• Location & Background
• Field Operation
• Data Collected
• Log Analysis
• Conclusion
•
Introduction
To check on the tool’s performance against a known fluid conductivity in large water bodies and to establish the percentage of tool’s accuracy under
controlled conditions (min. borehole influence) against ELOG tool.
Also, to compare both log response in various environments; alluvial, hard rock and open water
bodies
Location
•
Background
Induction log is a very useful tool to study subsurface stratigraphy and formation conductivities in water
well.
It uses EMF (~40KHz) to induce formation’s magnetic field which induced formation’s current flow which is
proportional to formation’s conductivity.
It works best in low resistivity (<100ohmm) formation or non-conductive medium (air).
•
Background
Interpretively, low conductivity value (i.e 50mS/cm) indicate very fresh water while high conductivity
value (i.e 1000mS/cm) indicates salty water.
Resistivity is a reciprocal of conductivity. Hence, the former can be computed from that of the latter.
•
Background
The tool has been 1st order-calibrated in RG’s factory in the UK.
A 2nd order calibration can be done using the available calibration loop with a known max.
conductivity value.
A ‘zero’ calibration can be done by holding the probe up in the air though practically it’s none existent
(only in the vacuum).
Field Operation
60m walk-way to the intake tower
6.0m drop
Station
Set-up
Depth encoder
WinchRope to secure the wheel
Tool’s Cable12V DC for winch
12V DC for micrologger
Equipment
Conductivity Meter model WTW Multi 350i
Sign as in slide #9
Equipment
centralizer
Calibration loop from RG
Induction (SIND) tool Flow-meter tool
Definition
• Conductivity(Siemens) = 1/ resistivity (ohm.m)
• Standard units of conductivity = microS/cm
• microS/cm = 10^4/ohm.m
Data Collected
• Fluid conductivity (microS/cm) by Conductivity meter
• Conductivity in (mS/m); Gamma in CPS plus (derived bulk resistivity) by SIND tool
• SNR, LNR(Ohmm); SP (mV); SPR (Ohm); Gamma (CPS) by ELOG tool
• No available conductivity data in DID’s archive for comparison and data integrity checking
Tabulated Data
Cond. meter possibly needs lab calibration
ELOG’s data needscomparing with external data for integrity check
Resistivity dataOff recommended range for SIND tool
Log Analysis
• Example 1 – shows tool’s min. operating range for resistivity is “zero” Ohmm
• Example 2 – shows tool’s max. operating range for resistivity ~100 Ohmm
• Example 3 – Shows log response in alluvial
• Example 4 – Shows log response in hard rock
Example 1 - Batu Dam
Showing “zero” conductivity readings before tool reaches water surface
Slide 18: SIND data_run01 Slide 19: SIND data_run03
Depth: 1.0m-6.0m (air column)
Air column – “zero” conductivity
Possible humidity effect
Water surface
(Tool’s min. range reached)
Air column – “zero” conductivity
Possible humidity effect
Water surface
(Tool’s min. range reached)
EXAMPLE 2 - Batu Dam
ELOG’s short resistivity vs. SIND’s derived resistivity in open water
bodies
Slide 21: SIND Data Slide 22: ELOG Data
Depth: 18m-23m
86Ohm.m ~11.9mS/m (119µS/cm)
(Value couldn’t hit beyond 100Ohmm due to to tool’s max. range reached unlike ELOG)
257Ohm.m Conductivity=10^4/Ohmm = 10000/257 = 38.9 ~ 39µS/cm
See slide#15 under ELOG
EXAMPLE 3- KLT017 (alluvium)
ELOG’s short resistivity vs. SIND’s derived resistivity in Alluvium
Slide 24: SIND Data
Slide 25: ELOG Data Depth: 61m-67m
SIND’s;15.46Ohmm
ELOG’s;23.55Ohmm
EXAMPLE 4 - SK198 (hard-rock)
ELOG’s short resistivity vs. SIND’s derived resistivity in hard rock.
Slide 27: SIND Data
Slide 28: ELOG Data Depth: 76m-82m
2.11 Ohmm
12.93 Ohmm
Conclusion
1. A consistent shift in resistivity values are observed from that of SIND & ELOG tools in
alluvial and hardrock environment.
2. Recommended resistivity operating range for SIND’s tool is between 0 – 100 Ohmm. Readings are unreliable beyond the recommended range
as shown in Batu Dam evaluation exercise.
Acknowledgements
1. DID, Northern Zone Div., Federal Territory – Tuan Hj Zul Mohamad, Mohd Ezla, Izrul Faris,
Bachtiar Effendi & Mohd Shariff
2. DID, Water Resources Management and Hydrology dept., Ampang – Yuhaslin, Khairul
Fadzilah