Regional overview of deep sedimentary thermal gradients of the geopressured zone of the Texas–Louisiana continental shelf

Abstract

Nearly 600 bottom-hole temperature data from the northern continental shelf of the Gulf of Mexico, each corrected for drilling disturbance, yielded a regional map of geothermal gradient down to approximately 6 km (3.7 mi) sub–sea floor. Two geographic trends can be seen on the map. First, from east to west, the geothermal gradient changes from values between 0.025 and 0.03 K/m (0.014 and 0.016°F/ft) off the Alabama–Mississippi shore to lower values of 0.015–0.025 K/m (0.008–0.014°F/ft) off eastern Louisiana and to higher values of 0.03–0.06 K/m (0.016–0.033°F/ft) off western Louisiana through Texas. Second, thermal gradients tend to be lower toward the outer continental shelf (less than 0.02 K/m [0.0112°F/ft]). We believe that the observed variations are primarily attributable to the thermal effect of rapid and regionally variable sediment accumulation during the Cenozoic era, which resulted in the occurrence of the geopressured zone in the Texas–Louisiana shelf. In the eastern Louisiana shelf, where accumulation was fastest, sediments down to about 6 km (3.7 mi) are relatively young (about