Abstract

Geothermal gradients have been calculated in 1131 fields and wells, and a map has been prepared showing the below-mudline depth to the 300° F subsurface isotherm over the northern Gulf of Mexico. Since the 300° F isotherm values are a direct reflection of thermal gradient, thermal conductivity and heat flow, the map may be considered as a portrayal of subsurface temperature distribution. Based on interpreted vertical and horizontal temperature patterns, the northern Gulf can be subdivided into six thermal domains. The Texas shelf domain shows the highest subsurface temperatures with a pattern of elongate, northeast-trending isotherm contours related to the regional pattern of faulting. A prominent temperature high perpendicular to the regional trend may reflect the southeast-plunging San Marcos arch. The High Island domain coincides with an Upper Miocene depocenter and has anomalously low temperatures caused by either a deep overpressure zone or shallow thermal conductive zone. Moderately high temperatures and a pattern of isotherm contours related to salt features characterize the Louisiana shelf domain. The Mississippi Canyon domain coincides with the Mississippi fan and displays very low temperatures due to thermal suppression from thick, rapid Quaternary sedimentation. The Walker Ridge domain coincides with the Texas-Louisiana slope and has the coolest temperatures found to date in the northern Gulf. The Alaminos Canyon domain falls within the Northwest slope and the Perdido diapir provinces and displays temperatures intermediate in value between the Texas shelf and Walker Ridge domains.