Toward the Scientific Interpretation of Geophysical Well Logs: Typical Misunderstandings and Countermeasures

Geophysical well log data are widely used in the field of structural geology, sedimentary geology and petroleum geology. Gaps and misunderstandings are still existing in the scientific interpretation of geophysical well logs. Logging environments and log curves need correction and standardization before interpretation, additionally, there are some special geological phenomena that will mislead the well log interpretation. This review critically highlights the typical misunderstandings existing in the well log data interpretation, and proposes countermeasures as well as scientific interpretation of well logs when encounter these misunderstandings. The factors that affect the well log data acquisition are summarized in terms of types of drilling muds, borehole stability and logging instrument rotation. The vertical resolution of various log series spans a wide range from 5 mm to about 10 m. In the field of structural geology, well logs can be used for determination of stratum attitude, fault recognition, fracture and in situ stress characterization as well as unconformity identification. Lithology and depositional facies can be interpreted using well logs. Well logs aim at finding hydrocarbons, and are used for source rock characterization and logging reservoir evaluation in the petroleum geology field. Then the typical misunderstandings and countermeasures in solving geological issues using geophysical well logs are reviewed from published papers as well as from the authors' personal experiences. This review will provide insights into the scientific interpretation of geophysical well log data, and help solving geological issues for the petrophysicist and geologist.