ABSTRACT:

While it is desirable to have a complete suite of logs to provide an interpretation the reality is that usually all we have to work with is a gamma ray/resistivity log. Log interpretation is often as much a geological exercise as a petrophysical one and background knowledge of local geology is critical in making many definitive interpretations based solely on limited logging data. With an understanding of diagenetic and sedimentological processes some otherwise confusing logging responses can be made clear. This informal presentation will show numerous examples of logging response utilizing various LWD technologies in clastic depositional environments. Fracture density can increase near faults and can create avenues for fluid migration when drilled overbalanced. An example will be discussed where the reason for fluid loss was determined to be due to an increase in fracture density near a fault drilled overbalance. The interpretation was made with an understanding of this process and based on gamma ray/resistivity data only. Soft sediment deformation is a common diagenetic process but can affect dip picks when utilizing low resolution gamma ray and bulk density image logs. Recognition of the problem will be discussed utilizing both high definition resistivity image logs and lower resolution gamma ray and bulk density image logs. With the onset of anoxia in the depositional environment authigenic minerals can be created. These minerals are conductive and can be observed as resistivity streaks. Several examples will be discussed. What appears to be sand on some LWD logs is not. These responses can be attributed to sweeps that are pumped to clean the hole and borehole washout. These effects can easily be recognized and several examples will be presented. Barriers to subsurface pressure equilibrium can be created at flooding surfaces. Several techniques will be discussed to trend gamma ray and resistivity data and recognize such surfaces. It will be shown that the good vertical resolution of LWD measurements and the minimal invasion close behind the bit simplify many interpretations. .

BIOGRAPHY:

Chester Young joined Baker Hughes INTEQ in January 1989 and is currently a Senior Geologist in the Formation Evaluation Group. He is also responsible for LWD Log & Data Quality for the North American Region and provides geological insight to the group. He graduated with a BS degree in Geology from Louisiana State University with scholarships from Mesa Petroleum and Louisiana Land & Exploration. He is a lifetime member of Phi Eta Sigma Honor Society and a Distinguished Honor Graduate from the U.S. Army Signal School. He is a 25 year member of AAPG and is a Board Certified Petroleum Geologist.