Chronology of the Bambucá Shale formation and its potential as source rock, western sector of the Neiva sub-basin – Huila, Colombia

Abstract

Improving the knowledge of Colombia's oil basins requires the evaluation and implementation of new strategies to enhance or increase the exploration of new hydrocarbon producing fields or encourage the deepening of geological studies in existing fields. In recent years, there has been a search for ways to maximize the production of hydrocarbon reservoirs, although in the country they have concentrated on the detrital type. This work proposes the search for formations containing carbonate rocks to expand the range of reservoirs of interest. In the work area, the Bambucá shale is characterized by having a high content of organic matter, but detailed information about its petrography, chronology and hydrocarbon potential has not been studied in detail. Carbonate reservoirs such as the Bambucá Shale contain abundant fossil record of microscopic marine brown algae known as calcareous nannofossils. These are an attractive study option to test or improve the resolution of historically assigned ages and evaluate the potential of a formation as a source rock. Preliminary analyses to propose a biozonation and biostratigraphic events of calcareous nannofossils in this formation allowed the identification of an assemblage composed of five predominant Cretaceous species (Cenomanian – Turonian): Quadrum svabenickae, Lithraphidites carniolensis, Calculites obscurus, Eiffellithus spp., and Watznaueria biporta, which are bioformers of the source rock in the study area and confirm the marine origin of sediments with organic matter capable of producing Type II kerogen.