--> Abstract: Petroleum Generation, Migration, and Distribution in the Northern Gulf of Mexico, by J. W. Kendrick and J. T. Thorleifson; #90987 (1993).

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KENDRICK, JOHN W., Shell Offshore Inc., New Orleans, LA; and J. T. THORLEIFSON, Shell Development Co., Houston, TX

ABSTRACT: Petroleum Generation, Migration, and Distribution in the Northern Gulf of Mexico

Although the origin and movement of petroleum in Cenozoic reservoirs of the Gulf of Mexico has stirred great debate, it is possible to construct a reasonable framework for petroleum generation and migration by analyzing the distribution and geological setting of oil and gas accumulations. Across the Louisiana-Texas continental shelf, there is a systematic change in petroleum composition from oil to gas as one proceeds west. The temperatures necessary to generate such hydrocarbons indicate that petroleum source rocks lie at considerable depth, and have been exposed to progressively higher temperatures in a westward direction. Mesozoic, or deeply buried Tertiary, beds are the likely source. The onset of hydrocarbon generation is controlled by the timing of significant sediment loading i any particular area, and seems to predate or to coincide with the deposition of reservoir sequences. In portions of offshore Texas, deeply buried source rocks may already have passed through the oil window before traps were formed during the Miocene.

The burial depths required for oil and gas generation further imply that vertical migration is essential for hydrocarbons to move from deep source to trap. The occurrence of accumulations comprising biogenic gas further implies that some traps have not had access to thermally generated hydrocarbons. Within the Gulf of Mexico salt province, the occurrence of oil and thermal gas can be explained by a model in which hydrocarbons enter reservoir sands at discrete points via deep-going structural elements, and, subsequently, migrate laterally, spilling away from the vertical entrypoint.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.