Abstract: Petroleum System Evolution in the Conecuh Embayment, Southwest Alabama, U.S. Gulf Coast

William J. Wade

Analyses of hydrocarbon maturation trends in Smackover reservoirs of southwest Alabama indicates that crude oils in updip reservoirs of the Conecuh Embayment are anomalously mature for their present temperature-depth regimes. It is inferred that these mature oils equilibrated to depth-temperature conditions in deeper reservoirs downdip, and subsequently re-migrated to their present positions. Burial history reconstructions, regional structure, and reservoir distributions support a model in which these mature oils leaked from the Jay-Flomaton-Big Escambia Creek field complex during Tertiary time, migrated through the Norphlet Formation, and accumulated in updip Smackover and Haynesville traps associated with basement knobs.

Geochemical evidence suggests that hydrocarbon leakage from the Jay-Flomaton-Big Escambia Creek complex may have been triggered by an influx of very mature gas condensates with high non-hydrocarbon gas contents from failed reservoirs still farther downdip. This scenario has potential implications for (1) predicting potential migration pathways and preferential areas of crude oil accumulation in the updip portions of the Conecuh Embayment; and (2) reinterpreting organic-inorganic burial diagenetic reactions in the Norphlet Formation reservoirs of offshore Mobile Bay.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas