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Petroleum Systems and Reservoir Appraisal in the Sub-Andean Basins (Eastern Venezuela and Eastern Colombian Foothills)

By
François Roure
François Roure
Institut Français du Pétrole, Rueil-Malmaison, France
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Nathalie Bordas-Lefloch
Nathalie Bordas-Lefloch
Institut Français du Pétrole, Rueil-Malmaison, France; Département de Géotectonique, University Paris-VI, France
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Jaime Toro
Jaime Toro
Institut Français du Pétrole, Rueil-Malmaison, France
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Charles Aubourg
Charles Aubourg
Laboratoire de Géologie, University of Cergy-Pontoise, France
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Nicole Guilhaumou
Nicole Guilhaumou
Département de Géotectonique, University Paris-VI, France
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Elisabeth Hernandez
Elisabeth Hernandez
INTEVEP-PDVSA, Los-Teques, Venezuela
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Sophie Lecornec-Lance
Sophie Lecornec-Lance
Institut Français du Pétrole, Rueil-Malmaison, France
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Carlos Rivero
Carlos Rivero
INTEVEP-PDVSA, Los-Teques, Venezuela
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Philippe Robion
Philippe Robion
Laboratoire de Géologie, University of Cergy-Pontoise, France
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William Sassi
William Sassi
Institut Français du Pétrole, Rueil-Malmaison, France
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Published:
January 01, 2003

Abstract

Major oil discoveries in the foothills of the Venezuelan and Colombian Andes have recently focused the interest of exploration companies toward sub-Andean basins. Seismic, well, and core data from the El Furrial (Venezuela) and Cusiana (Colombia) productive fields have been integrated herein with other regional information to document the evolution of the thrust belt and the history of the petroleum systems, and to propose practical guidelines for prediction of sandstone reservoir quality in such a complex geodynamic environment.

Although timing of deformation is slightly different in these areas of eastern Venezuela and Colombia, sedimentary and tectonic burial of the foreland autochthon in both regions led to the maturation of prolific Cretaceous marine source rocks, resulting in successive and diachronous hydrocarbon migration and trapping episodes.

Early sedimentary burial at the current location of the Serranía del Interior (Venezuela) and the Eastern Cordillera (Colombia) resulted in long-range migration of early-generated hydrocarbons toward the foreland, forming the large accumulation of hydrocarbon along the Faja Petrolifera (Eastern Venezuela). Early entrapped hydrocarbons also have been preserved in pre-Andean prospects of the Andean foothills, as evidenced by the complex charge history of the Cusiana field. However, wide areas of source rocks in the Andean foothills and adjacent foreland reached the oil window only during the late Neogene and Pliocene-Quaternary, when maximum burial was attained. This produced a second migration episode, coeval with the growth of frontal anticlinal prospects.

The main reservoir in Cusiana is fluvial sandstone of the Mirador Formation (Eocene); in El Furrial, it is sandstone of the Naricual-Merecure Formation (Oligocene). Pressure solution and quartz cementation decreased permeability of these sandstones. Results of studies of the anisotropy of the magnetic susceptibility (AMS), coupled with studies of fluid inclusions in quartz overgrowths and thermal modeling, demonstrate that sandstone reservoirs of these oil fields were compacted both vertically, by the load of the synflexural sequence, and horizontally, by tectonic stress (layer-parallel shortening) prior to being tectonically emplaced into the allochthon. Layer-parallel shortening by pressure solution is a major source of silica in the underthrust foreland.

Venezuelan and Colombian sandstones still have reasonably good reservoir characteristics, although they have been buried to great depths. Overpressure that developed in these reservoirs as a result of rapid foredeep sedimentation probably caused a delay in compaction. Early carbonate cements also may have contributed locally to prevent compaction until secondary porosity developed as a result of dissolution of this early diagenetic phase. Finally, development of structural closures and hydrocarbon trapping has resulted progressively in the shutting down of the hydraulic system, preventing the transport of exotic silica by regional fluid flow.

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Contents

AAPG Memoir

The Circum-Gulf of Mexico and the Caribbean: Hydrocarbon Habitats, Basin Formation and Plate Tectonics

Claudio Bartolini
Claudio Bartolini
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Richard T. Buffler
Richard T. Buffler
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Jon F. Blickwede
Jon F. Blickwede
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American Association of Petroleum Geologists
Volume
79
ISBN electronic:
9781629810546
Publication date:
January 01, 2003

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