RESISTIVITY LOG

NURUL AMALINA BINTI MOHD NOOR AZLAN 2014609316FAUZAN NAJIHAH BINTI MOHD FAUZI 2014422506NOR AMINAH BINTI KAMARUDZZAMAN 2014801558NURFATIEHAH BINTI ABDUL GHANI 2014403896NUR AMALINA EZRINA BINTI DZULKIFLI 2014459386

INTRODUCTION OF RESISTIVITY TOOLS

• Resistivity = ability of substance to impede flow of electrical current

• Differentiate hydrocarbon bearing zones from water bearing intervals

• Resistivity + porosity measurements = water saturation

• Types : 1. Laterolog – electrodes2. Induction – coils and magnetic fields

BASIC PRINCIPLE OF RESISTIVITY

INDUCTION LATERALOG

• Tool that able to measure conductivity with extremely highly resistive muds (oil-based muds or gas as the borehole fluid)

• Requires no direct contact with ground surface since it can be used by electromagnetic induction

• measuring resistivity in high salinity (low resistivity) muds

• Directly methods of measurement

• Less sensitive to culture noises

INDUCTION

• A magnetic field is generated by an AC electrical current flowing in a continuous coil.

• The magnetic field from the transmitter coil induces ground loop currents

• alternating magnetic field will induced a voltage in the receiver coil.

INDUCTION

SOURCE :

http://www.epa.gov/esd/cmb/GeophysicsWebsite/pages/reference/_img/fig368.jpg

LATERALOG

• Consists of an electronics section and a mandrel section.

• The mandrel supports the electrodes.• The measurement current emitted is forced to

flow laterally into the formation.• Measurement - deep resistivity and shallow

resistivity• The lateral log current path is basically a series

circuit consisting of the drilling fluid, Mud cake, flushed zone, 4 invaded zone and the virgin zone, with the largest voltage drop occurring over the highest resistance zone.

SOURCE: https://www.spec2000.net/text119fp/DLL.JPG

SOURCE :http://homepages.see.leeds.ac.uk/~earpwjg/PG_EN/CD%20Contents/GGL-

66565%20Petrophysics%20English/Chapter%2019.PDF

FACTORS THAT AFFECT RESISTIVITY

• Type of sediment

• Stratification

• Temperature

• Presence of metal and concrete pipes, tanks

• Sediments porosity and pore water

THE BASIC LOG RESPONSE (Environmental Effect)

• contamination of water of groundwater• distortions in resistivity• mudcake thickness cannot be directly measured

with logging tools• mud, mudcake, flushzone, and zone of transition

influence resistivity measurement • groundwater depth• lithology favorable for groundwater• detection of fractures• thinkness of overburden• geology structure

SOURCE :http://sofia.usgs.gov/publications/wri/02-4036/fig3wellillx.gifhttp://www.wellog.com/charts/borehole.jpg

ADVANTAGES

• the equipment is light, portable and inexpensive.

• qualitative interpretation of data is rapid and straightforward.

• it is flexible and can be used for various purposes.

• it can be use for both soundings and profiling.

• shallow investigation are rapid.

LIMITATIONS

• depth investigation require long cables and consume much field time.

• interpretation of complex geologic structure is difficult.

• present of metal pipes,cable and electrical ground an complicate intepretation.

• accuracy of depth determination is lower than with seismic techniques.

• degree of contamination /water quality• material variation

Presentation is about resisitivity log; Resisitivity is an ability of substance to impede flow of electrical current. It have two types which are induction log and laterolog. Resistivity log have several advantages and disadvantages; resistivity log is flexible and require long cable for depth investigation.