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Abstract

AAPG Bulletin, V. 99, No. 8 (August 2015), PP. 15371556

Copyright copy2015. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/04161511107

Petroleum system modeling in the Eastern Cordillera of Colombia using geochemistry and timing of thrusting and deformation

N. Sánchez,1 A. Mora,2 M. Parra,3 D. Garcia,4 M. Cortes,5 T. M. Shanahan,6 R. Ramirez,7 O. Llamosa,8 and M. Guzman9

1Instituto Colombiano de Petróleo, Ecopetrol, Bucaramanga, Colombia; [email protected]
2Instituto Colombiano de Petróleo, Ecopetrol, Bucaramanga, Colombia; [email protected]
3Institute of Energy and Environment, University of Sao Paulo, Sao Paulo, Brazil; [email protected]
4Instituto Colombiano de Petróleo, Ecopetrol, Bucaramanga, Colombia; [email protected]
5Instituto Colombiano de Petróleo, Ecopetrol, Bucaramanga, Colombia; [email protected]
6Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
7Escuela de Geología, Universidad Industrial de Santander, Bucaramanga, Colombia; [email protected]
8Departamento de Yacimientos, Occidental de Colombia, Bogotá, Colombia; [email protected]
9Instituto Colombiano de Petróleo, Ecopetrol, Bucaramanga, Colombia; [email protected]

ABSTRACT

In the present study, stratigraphic data from cores and outcrop sections are integrated with data on thermal maturity, organic facies, and thermochronometric information to reconstruct the tectonic and associated petroleum system evolution of the eastern foothills thrust belt along the Colombian Eastern Cordillera, one of the most prolific hydrocarbon provinces in northern South America. Sedimentary and tectonic burial of the foreland autochthon caused maturation of the Coniacian to Santonian shallow marine Chipaque Formation, resulting in successive and diachronous episodes of hydrocarbon migration and trapping. One-dimensional and two-dimensional maturation modeling indicates that oil generation from the Chipaque Formation began at the Paleocene-Eocene boundary (55 Ma) in the southern parts of what is now the Eastern Cordillera and progressed to the north. By the late Oligocene, tectonic inversion of the Eastern Cordillera exhumed most of these kitchens, terminating the oil generation from the Chipaque Formation. Kitchens migrated northward and eastward during the Oligocene and early Miocene. Because of the absence or subsequent erosion of traps, it is likely that the southernmost source rocks expelled most of their oil without any appreciable accumulation.

Our modeling indicates that there were two important kitchens during the Cenozoic. The larger of the two was located in the present-day Eastern Cordillera, and it was most productive in the late Eocene–early Oligocene. The second kitchen, which generated oil throughout the Neogene, was located in the foredeep of the Llanos basin, adjacent to the mountain front. Considerable amounts of oil from this recent pulse have accumulated in both deep and shallow reservoirs along the eastern foothills. The modeled reservoir charge history also explains the substantial biodegradation of oils in reservoirs that are today much too deep to support the process. Biodegradation must have occurred when the reservoirs were shallower and at cooler temperatures, and they remained active until the reservoirs were buried to depths where temperatures were high enough to prevent further bacterial activity.

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