Seismic profiling was used to choose five targetted locations for piston-assisted gravity coring efforts and geochemical profiling of sediments across a hydrocarbon seep site in the Gulf of Mexico. High frequency backscatter in the shallow-source deep receiver data suggested an accumulation of gas and/or hydrate in an area immediately adjacent to one of the sites primary faults. Coring efforts successfully retrieved hydrate from this location and geochemical profiling revealed elevated hydrocarbon concentrations relative to other sites across the mound. Isotope and hydrocarbon ratio evidence was used to infer that the source of hydrocarbons at this coring location was deep thermogenic reservoirs. Methane at the four remaining coring sites was dominated by biogenic methane with lesser contributions of thermogenic methane at some sites. Methane carbon isotope values were correlated with the depth of the sulfate methane transition zone across all coring locations suggesting that microbial activity across this fault complex is substrate limited. We use geochemical profiles to groundtruth seismic indicators of gas and hydrate occurrence in an effort to improve the predictive capabilities of this remote sensing tool.

Integrating seismic data and geochemical profiles to identify methane provenance, cycling, and migration pathways

245th National Meeting (2013)

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