AAPG Bulletin, V. 83 (1999), No. 7 P. 1068-1095.

Origin of Oil in the Sureste Basin, Mexico¹

M. A. Guzman-Vega² and M. R. Mello³

©Copyright 1999.  The American Association of Petroleum Geologists.  All Rights Reserved

¹Manuscript received August 22, 1996; revised manuscript received May 18, 1998; final acceptance December 4, 1998.
²Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas #152 CP 07730 Mexico D.F., Mexico; e-mail: [email protected]
³Petrobras/Cenpes, Cidade Universitaria, Ilha Do Fundão, Quadra 7 C.P. 21949-900, Rio de Janeiro-RR, Brazil.

This study represents a joint effort by Instituto Mexicano del Petróleo, Petróleos Mexicanos, and Petrobras Research Center, and it has benefited from the assistance of numerous people in Mexico and Brazil. We appreciate Baldomero Carrasco Velazquez, Raul Gonzalez García, Pablo Cruz Helu, and Noel Holguin for their continuous support. We thank the technical staff from CEGEQ/PETROBRAS for the data and analytical assistance. We are especially grateful to Ricardo Marins P. Da Silva for the drawings and all the final art. We appreciate the helpful comments of Wallace Dow, Alain Huc, Javier Meneses, and an anonymous reviewer who greatly contributed to the content and style of the manuscript. M. A Guzman deeply thanks his coauthor, M. R. Mello, for hours of input, discussion, and advice. 

ABSTRACT

Geochemical and biological marker analyses of oils and rock samples from the Sureste basin of Mexico were effective in identifying and geographically limiting four major oil families related by age and source rock depositional environment: Oxfordian, Tithonian, Early Cretaceous, and Tertiary.

The source rocks giving rise to the Jurassic and Cretaceous oils are associated with marine carbonate environments. In contrast, the source rocks giving rise to the Tertiary oils are associated with a marine deltaic siliciclastic depositional setting. Biomarker and isotope differences observed in the oils derived from marine carbonate environments can be interpreted in terms of salinity, clay content, and oxygen depletion variations. These differences provide diagnostic criteria for recognizing and differentiating five distinct organic-rich depositional regimes as the sources for these oil types: an anoxic hypersaline marine-carbonate environment associated with a narrow and shallow semirestricted sea (Oxfordian age, family 1 oil); an anoxic marine-carbonate environment associated with a silled basin geometry (Tithonian age, family 2 oils, subtype 2a); an anoxic marine-carbonate environment associated with a shallow, gentle, broad marine-carbonate ramp in a distal position (Tithonian age, family 2 oils, subtype 2b); a clay-rich suboxic/anoxic marine-carbonate environment associated with a carbonate platform in a proximal position (Tithonian age, family 2 oils, subtype 2c); and an anoxic marine-evaporitic environment (Early Cretaceous age, family 3 oils). The Tertiary oils (family 4) are derived from bacterially reworked terrigenous and marine organic source materials deposited in a marine-deltaic environment.

The Tithonian-related oils in the Mexican southern side of the Gulf of Mexico accumulated both offshore and onshore and throughout the stratigraphic column from Kimmeridgian to Pleistocene reservoirs, suggesting vertical pathways as the principal secondary migration mechanism. The lateral variations of these oils can be interpreted to reflect the Tithonian paleogeography in the area and could be useful in predicting differences in the oil compositions.