GEOTHERMICS OF THE ESSAOUIRA BASIN IN MOROCCO

The mean values of geothermal gradient and heat flow density have been estimated from bottom-hole temperatures taken from 75 petroleum exploration wells in the Essaouira basin in Morocco and are found to be 21.0 +/- 0.3 mK/m and 68 +/- 8 mW/m2, respectively. The regional thermal gradient varies with depth, from 30-35 mK/m near to the surface to about 18 mK/m between 2000 and 3000 m depth and then increasing again to over 24 mK/m at depths greater than 3000 m. The decrease at intermediate depths results from the presence of Triassic evaporites (with high thermal conductivities). Comparison of the temperature pattern and petroleum occurences indicates that the hydrocarbon matured in the deep Paleozoic formations and ascended from the source rocks by both upward migration along active faults and uplift during compressional