Compensated Geothermal Gradient Anomalies in a Mature Hydrocarbon Basin: Lake Pontchartrain, Lake De Cade, and Eugene Island, Gulf Coast, Louisiana

M. W. Ibrahim

The compensated geothermal gradient method is based on calculating the compensated geothermal gradient (CGG) and the correlative extrapolated surface temperature intercept (ESTI) of control wells by using statistical linear regression on corrected bottom-hole temperatures, then graphically analyzing the ESTI-CGG relationship with each other and to the sources of data (i.e., producing, suspended, or dry wells), and finally contour mapping both the CGG and the ESTI to delineate anomalous association of both with hydrocarbon-producing wells, fields, and areas, and to infer prospective areas and bypassed areas.

The method has been tested on areas in the Middle East, Africa, and on the Gulf Coast of Louisiana. Results reveal (1) a common inverse relationship of CGG to the ESTI in all areas, (2) the Lake Pontchartrain area expresses anomalous association of low CGG and high ESTI in oil and gas field locations, (3) the Lake De Cade area displays an anomalous association of high CGG and low ESTI with oil and gas field locations, and (4) no anomalous association with oil and gas fields was observed at Eugene Island.

Potential applications of this method are in screening mature basins for remaining prospective acreage and in selecting wells or areas for detailed investigation.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.