WELL LOG (The Bore Hole Image)
Well log is a continuous record of measurement made in bore hole respond to variation in some physical properties of rocks through which the bore hole is drilled.
Traditionally Logs are display on girded papers shown in figure.
Now a days the log may be taken as films, images, and in digital format.
1912 Conrad Schlumberger give the idea of using electrical measurements to map subsurface rock bodies.
in 1919 Conrad Schlumberger and his brother Marcel begin work on well logs.
The first electrical resistivity well log was taken in France, in 1927.
The instrument which was use for this purpose is called SONDE, the sond was stopped at periodic intervals in bore hole and the and resistivity was plotted on graph paper.
In 1929 the electrical resistivity logs are introduce on commercial scale in Venezuela, USA and Russia
For correlation and identification of Hydrocarbon bearing strata.
The photographic – film recorder was developed in 1936 the curves were SN,LN AND LAT
The dip meter log were developed in 1930
The Gamma Ray and Neutron Log were begin in 1941
Logging service companies utilize a variety of logging units, depending on the location (onshore or offshore) and requirements of the logging run. Each unit will contain the following components:
winch to raise and lower the cable in the well
self-contained 120-volt AC generator
set of surface control panels
set of downhole tools (sondes and cartridges)
digital recording system
depth to lithological boundaries
in-situ stress orientation
Depth Of Investigation Of Logging Tools
The objective of log interpretation depends very much on the user. Quantitative analysis of well logs provides the analyst with values for a variety of primary parameters, such as: