New Geochemical Characterization of Natural Gas and Its Use in Oil and Gas Evaluation
Published:January 01, 2000
A. Prinzhofer, M.R. Mello, L.C. da Silva Freitas, T. Takaki, 2000. "New Geochemical Characterization of Natural Gas and Its Use in Oil and Gas Evaluation", Petroleum Systems of South Atlantic Margins, Marcio Rocha Mello, Barry J. Katz
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Gas signatures are used to characterize the processes occurring from generation of hydrocarbons in source rocks to their accumulation in reservoirs. Two main geologic parameters to consider are the maturity of the hydrocarbons (primary cracking of kerogen or secondary cracking of oils) and their degree of segregation during transport, linked to a migration distance. Several new diagrams and geochemical parameters are now suggested to characterize the directions and distances of migration of gases more quantitatively Two examples from Brazil include the Ceará Basin and the Recôncavo Basin. In the Ceará Basin, a gas geochemical study shows that normal faulting associated with rifting of the passive margin has locally altered the global direction of hydrocarbon migration. Such estimations of global and local directions of hydrocarbon migration allow a better reconstruction of the filling of geologic traps with hydrocarbons. The Recôncavo Basin case study shows our enhanced ability to distinguish bacterial activity, mainly in the central part of the basin, from segregative transport, more visible in the southern part. We demonstrate the efficiency of a major fault (the Mata–Catu fault) as a conduit along which hydrocarbons migrate to distances of 40 km away from the oil kitchen. These geologic examples using gas geochemical and isotopic signatures provide a platform for further applications of these tools in modeling of hydrocarbon migration and accumulation for both basin exploration and reservoir estimation.
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Petroleum Systems of South Atlantic Margins
“Giant oil and gas fields have been discovered through recent exploration in the deep and ultra-deep water regions of Angola, Brazil, and Nigeria. This volume includes 1. Descriptions of the petroleum geology of more than 12 basins along the two margins 2. Discussion of various components of the petroleum systems within these basins 3. Discussion on the use of the petroleum systems concept in the South Atlantic marginal basins to classify and characterize the diversity of the systems 4. Methodologies used in the assessment of petroleum system components 5. Overviews of the different components of the region's petroleum systems. Petroleum explorationists and researchers working in the South Atlantic will welcome this addition to their libraries.
The printed version of Memoir 73 was the Winner of the 2000 Dott Award for best AAPG Special Publication.”