Observations suggest that deep overpressured sediments in the U.S. Gulf Coast Sedimentary Basin are expelling porewaters vertically near the flanks of some salt domes. The project will numerically model flow fields, brine plumes and thermal anomalies that may result around generic salt domes by this process. The numerical modeling will incorporate the effect of dewatering a thick overpressured sedimentary section deeper than 3 to 4 km, with fluid expulsion preferentially upward near the flanks of the domes. The modeling will also incorporate the effect of instabilities induced by porewater density gradients due to salinity and temperature variations. In parallel, subsurface salinities, temperatures and pressures will be mapped in vertical cross-sections across eight salt domes in the U.S. Gulf Coast, using borehole logs to determine whether basin dewatering is manifested by brine plumes and thermal anomalies. The proposed work may help explain the origin of 1)heavy metal sulfide deposits and diagenetic minerals precipitated above or on the flanks of salt domes, at temperatures tens of degrees above that of host sediments, and 2)perched brine plumes above the salt domes, gravitationally unstable by virtue of their high density. The work proposed here may also shed some light on mechanisms for hydrocarbon migration because hydrocarbons often occur on the flanks of salt domes above overpressed sediments.
