Geothermal Gradient anomalies have long since been recognised to accompany hydrocarbon traps. The anomalies are most probably byproducts of heat transporting processes of hydrocarbon migration and entrapment. Therefore, couldn't identical anomalies be used to locate undiscovered or bypassed traps?
This study used BHT data of exploration and development wells in UKCS guadrants 35 to 54 of the North Sea to: produce contour maps of the geothermal gradients, identify geothermal gradient anomalies associated with proven hydrocarbon traps then use the models identified to delineate potentia, probable and possible anomalies indicative of undiscovered hydrocarbon traps or migration paths in the same quadrants.
A computer programme (CGG-ESTI) was used to correct and test for reliability the BHT records of 238 wells in order to identify boreholes with statistically significant BHT data. Discriminative computer contouring technique was used to produce noninteractive, un-biased contours similar to the manual after-the-fact contours. This technique utilised statistically significant as well as undifferentiated control points to generate compensated geothermal gradient contours (CGG), extrapolated surface temperature intercept contours (ESTI) and map geothermal gradient anomalies of hydrocarbon entrapment.
The study delineated 50 PROVEN and 46 POTENTIAL, PROBABLE and POSSIBLE geothermal gradient (CGG-ESTI) anomalies of hydrocarbon entrapment.