Insights from Cretaceous Fluid Inclusions in Mississippi and Louisiana

Cretaceous Tuscaloosa Group sandstone core samples from 13 wells were collected across Mississippi and Louisiana for fluid inclusion analysis. Petrographic observations indicate the presence of both aqueous and hydrocarbon fluid inclusions, which record the minimum entrapment temperature of the fluids via homogenization temperatures (Th). Aqueous inclusion Th can be relatively close to entrapment temperatures and thus potentially estimate maximum burial temperatures, assuming no post-entrapment alteration and a consistent regional thermal gradient through time. The maximum Th values relative to corrected current sample depth temperatures indicate ~150–900 meters of exhumation along the Southern Mississippi Uplift. Inclusions from the Central Mississippi Salt Basin samples indicate little to no uplift. Further, Th are highest in the south and decrease to the north, broadly following the Tuscaloosa Group depth trend. API gravity estimates calculated using hydrocarbon inclusion fluorescence coupled with microthermometry indicate the highest maturity hydrocarbons are along the Southern Mississippi Uplift, with values of 39–46° to the south (blue fluorescing inclusions) that decrease to 36–39° in the north (both blue and white fluorescing inclusions). The hydrocarbon inclusions fluoresce yellow in the Central Mississippi Salt Basin, indicating lower maturity (no API gravity estimate). The thermal maturity of the oils is based on the temperature at which the hydrocarbons were generated, which parallels the burial temperature trend. These interpretations can be further utilized with available geochemical and thermal maturity parameters to provide key insights for Cretaceous strata in this area to improve understanding of the thermal history variability in the region.