Thermal Evolution of Potential Cretaceous and Tertiary Source Rocks across the MMVB, the Southern Portion of the Eastern Cordillera, and Llanos Basin Foothills, Colombia

Martínez, Maria A.¹; Mora, Andrés; and Lelijveld, Jaron
¹[email protected]

A quantitative hydrocarbon charge modeling was performed along a NW-SE regional 2D structural cross section across the MMVB, southern portion of the Eastern Cordillera, and Llanos Basin Foothills, a highly tectonically complex setting, to evaluate the thermal evolution of hydrocarbon generation areas and determine migration time and pathways, in order to assess hydrocarbon trapping process and mixtures from potential Cretaceous and Tertiary source rocks for the southern Llanos Basin. Identification of potential new opportunities is a secondary objective.

The procedure included the kinematic restoration of the structural cross section at five different stages, where main tectonic events occurred. Lateral and vertical facies changes of source, reservoir, and seal intervals were included. Five potential source intervals were considered, two from the Lower Cretaceous, one from the Upper Cretaceous, and two from the Paleogene, based on previous geochemical studies. Three different thermal heat flow histories were used along the section, according to the tectonic evolution of the area. They were calibrated using new thermochronometric and VR data from outcrops in the Eastern Cordillera, and VR and BHT data from wells located in the Llanos foothills. Several scenarios were simulated considering different migration methods, fault properties, and source rock kinetics.

Modeling results suggest the Lower Cretaceous potential source rocks had their main generation and expulsion episodes during the Aptian-Coniacian, and the Upper Cretaceous potential source rock from Early Paleocene to Late Oligocene. Paleogene potential source rocks were affected by the Eastern Cordillera uplift, and subsequent erosion since Early Miocene. Therefore, they barely entered the oil window in the Llanos foothills. Migration pathways are preferentially vertical and lateral towards the southern Llanos Basin.

A pod of active Cretaceous source rocks was identified in the central and eastern portions of the Eastern Cordillera, from Aptian to Late Oligocene times. Hydrocarbon accumulations identified in the foothills and the southern Llanos Basin are sourced mainly from the Upper Cretaceous potential source rock. Potential new opportunities identified in the Llanos foothills would be sourced from Lower Cretaceous source intervals. Most hydrocarbons generated by these rocks would have migrated to the southern Llanos Basin, where the main Cretaceous reservoirs were not yet deposited.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013