Hydrocarbon Source and Charge in the Neogene in the Macuspana and Veracruz Basins, Mexico

By

TALUKDAR, S. C.

Consultant, The Woodlands, TX,

GUEVARA, E. H., and JONES, R. H.

GALINDO, AGUSTÍN

PEMEX Exploración y Producción, Veracruz, México,

ROMERO, M. A.

PEMEX E y P, Ciudad del Carmen, México,

WAWRZYNIEC, T. F.

3D Structural Consulting, Minneapolis, MN,

VILLANUEVA, LAURA

PEMEX E y P, Coatzacoalcos, México,

FOUAD, KHALED, AMBROSE, W. A., JENNETTE, D. C., and DUNLAP, D. B.

Bureau of Economic Geology,

MENESES-ROCHA, J. J.

PEMEX E y P, Villahermosa, México,

SÁNCHEZ-BARREDA, LUIS

Bureau of Economic Geology,

LUGO, J. E.

PEMEX E y P, Villahermosa, México

Gas accumulations in Neogene reservoirs in the Veracruz and Macuspana Basins of Mexico contain mostly thermogenic-biogenic gas mixtures in different proportions. Biogenic gases may be locally volumetrically important in shallow reservoirs generally away from major deep faults, but pure biogenic gases are rare in the known reservoirs.

Immature Miocene and Pliocene shales sourced biogenic gases in the two basins. Thermogenic gases were generated and migrated from deeper Tertiary shales and Mesozoic shales and limestones. Assessment of organic richness, quality, and present-day maturity distribution of Mesozoic, Paleogene, and Miocene source rocks, and 1D maturity and hydrocarbon generation modeling, indicate that the thermogenic gas generation from the Mesozoic sources is much more significant than that from Paleogene and Lower Miocene sources. Timing of gas generation and migration from the Mesozoic and Paleogene sources in relation to the timing of trap formation, and the existence of vertical migration pathways (major faults) are the critical factors that controlled migration of the thermogenic gases for accumulation in the traps with Neogene reservoirs and seal. Traps connected by faults to the Mesozoic sources had the possibility of receiving greater thermogenic gas charges.