Master of Science (MS)
Geology and Geophysics
Sediments located in the vicinity of salt structures in the northern Gulf of Mexico have highly complex structures and fluid dynamics associated with the dissolution and diapirism of salt. Past studies (Lin and Nunn, 1997; Bruno and Hanor, 2003; Richards, 2013) have shown that faults associated with salt structures can act both as migration pathways and barriers to the flow of formation waters. Bruno and Hanor (2003), Steen et al. (2011), and Richards (2013) also demonstrated that lithology was a controlling factor in the flow of formation waters. In this study, two sets of wireline logs, one used in salinity mapping and the other used in temperature mapping, combined with structural interpretations from a 3D seismic volume were used to investigate how faulting and lithology controlled the migration of saline formation waters above a near-shore salt structure in the northern Gulf of Mexico. By using the Revil et al. (1998) method of calculating salinity from continuous digital gamma and resistivity logs, along with other parameters, it was shown that sand-dominated intervals had higher salinity values than shaly intervals. The calculated salinity curves also demonstrate that salinity is much lower in the pore water of the shale-dominated overpressure zone (<100g/L) than in the overlying sand-dominated zone (100-250 g/L). Two areas were identified where faults offset salinity values, suggesting that faults may impede the flow of formation waters in this region and that some faults are younger than brine migration. Temperature and salinity mapping at two depths (6000 and 1000 ft SSTVD) combined with fault interpretations from seismic showed that faulted regions have elevated temperatures and salinities. This suggests that warmer formation waters are migrating upward along the fault from the deeper overpressured zone into the overlying hydrostatically pressured hypersaline zone, as suggested by Lin and Nunn (1997).
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McCollum, Candice M., "Variations in Salinity and Temperature on the Flank of an Offshore Louisiana Salt Structure" (2014). LSU Master's Theses. 2309.