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

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, the anticlines that exhibit conspicuous double-plunging three- or four-way closures that are preferentially located in the region immediately north of Bogotá within the Axial Zone were first documented. The main structural style was then illustrated with balanced cross-sections. After this type of structure had been identified, 19 one-dimensional petroleum systems models were produced in the adjacent synclines to assess the timing of generation and migration of petroleum using optimistic source-rock parameters. Two different scenarios were modelled, one of them having an additional 900 m of deposited Paleogene sediments. Based on these models, maps for the transformation ratio and hydrocarbon expulsion from the main source rock (the Chipaque Formation) were created in order to assess the timing of the main generation and expulsion. This allowed us to document that the main phase of generation occurred between the Late Eocene and the Middle Miocene. Previous studies have supported the idea that the main structures had formed by the Late Oligocene–Early Miocene. Based on this, it was concluded that it would have been possible for gas and light crude oil accumulations to have formed at that time but there was the problem of their preservation. However, the modelling of petroleum generation in the updip sectors of the potential kitchens may suggest an undiscovered potential that has not previously been documented.