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The AAPG/Datapages Combined Publications Database
AAPG Special Volumes
Abstract
2003. The American Association of Petroleum Geologists. All rights reserved.
Late Cretaceous Carbonate Reservoirs in the Cordoba Platform and Veracruz Basin, Eastern Mexico
Salvador Ortu
o-Arzate,1 Helga Ferket,2 Marie-Christine Cacas,3 Rudy Swennen,2 Fran
ois Roure3
1Instituto Mexicano del Petrleo, M
xico, D.F., Mexico
2University of Leuven, afdeling Fysico-chemische geologie, Heverlee, Belgium
3Institut Franais du P
trole, Rueil-Malmaison Cedex, France
ACKNOWLEDGMENTS
This work benefited greatly from the technical assistance of PEMEX and IMP. Guillermo Perez and Noel Holguin provided all the support and enthusiasm necessary to organize the PEMEX-SUBTRAP-IFP field seminar in Veracruz and Cordoba, and initiated this international collaboration. The University of Cergy (Dominique Frizon de Lamotte) provided drilling tools for collecting oriented plugs in the field. Dominique Gurillot (IFP), Ricardo Caraveo, and Miguel Espinoza (PEMEX) also participated in the field work. Ricardo Caraveo and Miguel Espinoza, together with Modesto Landeros, also were very helpful in collecting core samples in Veracruz. Francine B
nard handled preliminary runs of Genex and Gentect on some of the wells. Herman Nijs prepared all the thin
sections
. We also would like to thank Chris Johnson and an anonymous reviewer for their helpful suggestions on an earlier draft of this paper.
ABSTRACT
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 (
1) 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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