Tectonic Evolution and Petroleum Systems of the Llanos Basin, Colombia

Abstract

Abstract

The Llanos basin is characterized by a southern province with biodegraded oils (API gravities <20°) and a central province (Casanare province) of oils with API gravities >20°. However, it has been difficult to develop a model that explains the reason for such spatial zonation. In this work we used multiple 1D T-t models to map the kitchens for 3 different source rocks and compare its maturity level throughout the Cenozoic succession with the presence or absence of reservoir, seal, overburden and traps in a series of maps of the Llanos basin. We find that the Llanos basin petroleum systems may have been governed by a shared evolution with the adjacent orogenic belt in which initial Paleogene stratigraphic traps dominated in the south, as favored by more-segmented basement and potentially transpressional stresses, followed by a Neogene phase with pervasive east-dipping, low-displacement normal fault traps, then a final Pliocene to Recent phase of contractional traps in foothill areas. When compared with the evolution of hydrocarbon kitchens, we suggest that Upper Cretaceous source rocks from the Eastern Cordillera dominate in the heavy biodegraded oils to the south, whereas Lower Cretaceous source rocks from the foothills charged more terrigenous Upper Cretaceous facies during Neogene formation of younger contractional traps in the foothills. This evolution precludes the presence of large accumulations comparable in size to the Orinoco heavy oil belt of the Llanos basin.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016