resistivity log
DESCRIPTION
resTRANSCRIPT
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.