| The Block 330, South Eugene Island, in the Gulf of Mexico, is an area where reservoirs deposited during the Late Pliocene and Pleistocene were filled by hydrocarbons. These reservoirs could have been charged by oil and gas migrating up a major normal fault (the Red Fault) in the last 0.46 ma. Rapid and recent hydrocarbon migration up a fault could produce a monopolar positive temperature anomaly along the fault.; This work addresses, through a numerical finite element modeling, the following geologic controls that could affect the temperature field in the Block 330: presence of salt domes and their geometry, differences in compaction between the upthrown and downthrown sides of the Red Fault, lithological and mineralogical changes in the sediments, local radioactive heat generation, local heat flow, the presence of hydrocarbons and the time spent to fill the reservoirs and adjacent shales. These controls were evaluated by making many 2D temperature calculations (a numerical sensitivity analysis).; The main conclusion is that hydrocarbons reduce the thermal conductivity of the fluids in the sediments in such a way as to reproduce the dipolar anomaly of up to -5{dollar}spcirc{dollar}C observed above the reservoirs with hydrocarbons and the associated positive anomaly of up to 10{dollar}spcirc{dollar}C, observed below them. The broader dipolar anomaly produced by the hydrocarbons is detected by the scattered bottom-hole temperature data in the area whereas the much narrower monopolar positive anomaly produced by a hot plume moving along the fault is not.; The calculations show that hydrocarbons were most probably generated below the local salt sill that forms the base of the minibasin hosting the Block 330 reservoirs, and not in the Miocene sequence above it. Analysis also shows that normal compaction is different on the two sides of the Red Fault. The calculations suggest that if extensive hydrocarbon accumulations were situated over deeper salt domes they could offset the cooling effect in the sediments produced by the salt dome at its base. Vitrinite reflectance data suggests that at times there must have been very localized and short lived fluid migration along the Red Fault. |
