Petroleum systems modelling in thick-skinned structures: an assessment of potential accumulations in the Axial Zone of the Colombian Eastern Cordillera

Abstract

The main anticlines in the Axial Zone of the Eastern Cordillera are conspicuous geomorphic features that can be detected with remote sensing images and geological mapping. In this work first we document the anticlines that exhibit conspicuous double plunging 4-way closures or 3-way closures, which are preferentially located in the region immediately north of Bogotá within the Axial Zone. We illustrate the main structural style with balanced cross sections. After we identified this type of structure, we produced 19 1D petroleum systems models in the adjacent synclines to assess the timing of generation and migration using optimistic source rock parameters. We modelled two different scenarios, one of them with additional 900 m of deposited Paleogene sediments. Based on those models we created maps of transformation ratio and hydrocarbon expulsion from the main source rock (The Chipaque Formation) so that we can assess the timing of the main generation and expulsion. That allowed us to document that the main phase of generation occurred between the Late Eocene to Middle Miocene. Previous studies supported the idea that the main structures were formed by the Late Oligocene to Early Miocene. Based on that we conclude that there would be possibilities of having gas and light crude oil accumulations formed at that time, but the problem around them would be their preservation. However, modelling generation in the up-dip sectors of the potential kitchens may suggest an undiscovered potential that has never been documented.