Master of Science (MS)
Geology and Geophysics
Salt dome dissolution in the Gulf of Mexico sedimentary basin is a primary cause for elevated pore water salinities in the subsurface. Temperature, pressure, salinity, lithology and fluid density are parameters often used to identify preferential conduits and driving forces for fluid migration. These parameters were calculated using 20 wireline logs covering 40 km² on the south flank of a salt dome on the continental shelf, offshore Louisiana. 3-D seismic has been utilized to determine location of faults, to aid in sand correlation, and to provide a structural overview of the dome. Vertical and lateral variations in lithology, salinity, temperature, pressure, and fluid density were documented. The shallowest beds investigated are Pleistocene, hydrostatically pressured, shale dominated, nearly horizontally oriented, and contain waters of approximately marine salinity (35 g/L). The deepest section contains Miocene, shale dominated, south dipping sediments with salinities slightly greater than marine. The middle regime contains Pliocene sediments with pore waters up to 5 times marine salinity. Over 90 percent of this section is gross sand. Salt dissolution has generated dense, hypersaline brines that appear to be migrating downdip through the thick Pliocene sandy section. Sands that come in contact with or near the salt/sediment interface tend to contain pore waters with relatively higher salinities. Reservoir continuity can be inferred from seismic data, but discontinuities that are not ascertained through seismic data can be validated by sharp salinity contrasts. Fluid compartmentalization across a normal supradomal fault is evident and the offset of salinity contours are consistent with the throw of the fault. This suggests that hypersaline brines were migrating before the formation of the fault and that salt dissolution could be contributing to extensional forces that lead to normal faulting.
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Steen, Andrew Kevin, "Spatial Variations of Salinity, Temperature and Pressure on the Flank of a Salt Dome, Offshore Louisiana: Implications for Mechanisms of Fluid Flow" (2010). LSU Master's Theses. 1.