Tips
Sample Examination and Logging
Proper sample examination is essential for accurate geological analysis. Learn the recommended methods of logging, interpretive and percentage systems, and how to assess formation contacts and sample quality to produce reliable geological records.
SAMPLE EXAMINATION
- Sample studies should be made carefully.
- Accuracy depends on the quality of the samples and the skill of the observer.
METHODS OF LOGGING
There are two general methods of sample description and logging:
Interpretive System
Preferred method
Depends on the quality of samples and the geologist’s familiarity with the section
Formation contacts should be picked primarily from samples, not mechanical logs
Mechanical logs and drilling time logs can be useful to define unit boundaries and zones of porosity
Percentage System
After removing obvious foreign matter and unquestionably caved material, plot each rock type with symbols proportional to its percentage in the sample
Advantageous in areas where:
Stratigraphy is unknown
Samples are of poor quality
No mechanical logs are available
Stratigraphic sequence is interrupted by structural complications
The observer is inexperienced
PERIODIQUE TABLE