Sample studies Should be made carefully. The Accuracy is dependent upon the quality of the samples and the skill of the observer.
METHODS OF LOGGING
There are to general methods of sample description and logging, the interpretive system and the percentage system. the interpretive log is preferable but depends on the quality of the samples and the geologists' familiarity with the section.
Although formation contacts should be picked on the basis of the sample rather than on mechanical logs, the latter, as well as drilling time logs, can be useful in defining boundaries of specific units and zones of porosity.
In percentage logging, after eliminating the obvious foreign matter and unquestionable caved material, plot each rock type with a width of symbols proportional to its percentage in the sample. The system of logging may be used to advantage in areas where:
- Stratigraphy is unknown.
- Samples are poor quality.
- No logs are available.
- Stratigraphic sequence is interrupted by structural complications.
- The person studying is inexperienced