Late Cretaceous Carbonate Reservoirs in the Cordoba Platform and Veracruz Basin, Eastern Mexico
Salvador Ortuño-Arzate, Helga Ferket, Marie-Christine Cacas, Rudy Swennen, François Roure, 2003. "Late Cretaceous Carbonate Reservoirs in the Cordoba Platform and Veracruz Basin, Eastern Mexico", The Circum-Gulf of Mexico and the Caribbean: Hydrocarbon Habitats, Basin Formation and Plate Tectonics, Claudio Bartolini, Richard T. Buffler, Jon F. Blickwede
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This study focuses on the deformation history and hydrocarbon plays of Late Cretaceous carbonate reservoirs of the Cordoba Platform and adjacent Veracruz Basin. Here, the buried Laramide thrust front accounts for one of the most mature petroleum provinces of Mexico. Three regional structural cross sections across the Cordoba Platform have been constructed using available surface and subsurface geological and geophysical data, from the Sierra de Zongolica in the west to the Veracruz Basin in the east. Forward kinematic modeling of these transects, using the Thrustpack software, allowed reconstruction of the burial history of potential source rocks. One-dimensional and two-dimensional thermal modeling (using the Genex, Gentect, and Thrustpack models) allowed reconstruction of the petroleum generation history (i.e., the maturation history of potential source rocks) and the thermal evolution of carbonate reservoirs, wherein only conductive heat transfer was considered. Maximum temperatures in the Late Cretaceous reservoirs of the Cordoba Platform probably never exceeded 60°C. In contrast, the deeper duplexes located in the buried thrust front reached their maximum burial and peak temperature only very recently as a result of the Cenozoic subsidence history of the Veracruz Basin. This modeling showed that potential source rocks did not reach the oil window prior to post-Laramide episodes of burial. This means that hydrocarbons migrated essentially from east to west and upward from the Veracruz Basin and underthrusted foreland toward the productive duplexes of the buried Laramide thrust front. Microtectonic and diagenetic studies from outcrops helped in unraveling the importance of stylolite and (paleo)karst development and fracturing, and to better understand the structural control on the overall porosity and permeability of the reservoirs. Petrographic studies of outcrops and core material showed that the paleoenvironment accounts for the preservation of reasonably good matrix porosity in distinct lithofacies (i.e., in early dolomitized platform carbonates of the Orizaba and Guzmantla Formations, bioclastic wackestone to packstone in the Guzmantla Formation, and in slope breccias of the San Felipe Formation). An important factor controlling the development of secondary porosity in the Cordoba Platform carbonates appears to relate to two successive karstification episodes. The first episode was related either to global sea-level changes during the passive margin evolution or to the early development of a former Laramide flexural bulge, whereas the second karstification event postdates Laramide contractional episodes. Furthermore, hydraulic fracturing, which predates the development of bedding-parallel stylolites, is locally evidenced. They are interpreted to relate to vertical dewatering processes occurring in a dominantly extensional system. A second hydraulic fracturing postdates the bedding-parallel stylolites but predates the Layer Parallel Shortening (LPS) features. Overpressures during this second episode of hydraulic fracturing, which also locally affects the sealing strata, was mostly synchronous with the onset of the Laramide orogeny and occurred when the principal stress axis (σ1) was already horizontal. Deformation features accounting for secondary porosity developed during the Laramide orogeny. These still act locally as vertical conduits for the fluids and eventually display fair-to-good porosity and permeability, especially in the extrados and near the lateral anticlinal closures or at places where their overall orientation is consistent with the post-Laramide (modern) stress pattern.
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The Circum-Gulf of Mexico and the Caribbean: Hydrocarbon Habitats, Basin Formation and Plate Tectonics
The Circum-Gulf of Mexico and the Caribbean has long been one of the world's most important petroleum provinces, as well as one of the world's most geologically complex regions. These two characteristics have resulted in an extensive amount of ongoing research by both industry and academia. AAPG Memoir 79, The Circum-Gulf of Mexico and the Caribbean, is the first volume in more than a decade to document such a wide range of research on the geology of this vast area. Of the total 44 papers, roughly two-thirds pertain to the Gulf of Mexico, with an emphasis on the Mexican portion of the basin, and to the petroliferous areas of the southern Caribbean, including Colombia, Venezuela, Cuba, and Trinidad and Tobago. The remaining papers relate to the Antilles and Central America, as well as a series of papers that address region-wide topics such as plate tectonic evolution. A significant number of papers were contributed by authors from national oil companies and universities from within the region.