ABSTRACT

Seismic reflection and bottom hole temperature (BHT) data have been utilized for subsurface temperature investigations of two locations within the Gulf Coast Salt Basin in South Louisiana. A one-dimensional thermal model was constructed to analyze the subsurface temperature distributions. The model utilizes a relationship between seismic travel time and thermal conductivity and attempts to characterize the temperature variation due to conductivity variation. Subsurface maps and cross-sections were prepared for observed bottom hole temperature, model predicted temperature, and residual (observed minus predicted) temperature.

Results of the study indicate that the one-dimensional model predicted temperatures represent the major component of the observed temperature, which implies that the dominant mode of heat transport in the study areas is conduction. The persistence of thermal anomalies in the residual temperature maps, calculated by subtracting modeled temperature from observed temperature, implies that the thermal anomalies are not due to conductivity variations. The unique association of temperature anomalies with growth faults and the top of the geopressured zone strongly suggests that the anomalies are primarily caused by vertical and restricted lateral fluid migration. The growth fault segments associated with the anomalies are interpreted as permeable zones which act as conduits for vertical fluid migration. The higher hydraulic head gradient associated with the geopressured zone is the driving force for the vertical migration.

The heat flow in both areas is found to be 0.71 hfu (30.00 mW/sq. m). The average thermal conductivity is approximately 0.003 cal/ cm/s/^OC (1.350 W/m/^OK).