Hydrocarbon indication in Rio Bonito Formation sandstone: Implication for CO2 storage in São Paulo, Brazil

Abstract

São Paulo State has witnessed CO2 storage-based investigations considering the availability of suitable geologic structures and proximity to primary CO2 source sinks related to bioenergy and carbon capture and storage (BECCS) activities. The current study presents the hydrocarbon viability evaluations and CO2 storage prospects, focusing on the sandstone units of the Rio Bonito Formation. The objective is to apply petrophysical evaluations with geochemical inputs in predicting future hydrocarbon (gas) production to boost CO2 storage within the study location. The study used data from eleven wells with associated wire-line logs (gamma ray, resistivity, density, neutron, and sonic) to predict potential hydrocarbon accumulation and fluid mobility in the investigated area. Rock samples (shale and carbonate) obtained from depths >200 m within the study location have shown bitumen presence. Organic geochemistry data of the Rio Bonito Formation shale beds suggest they are potential hydrocarbon source rocks and could have contributed to the gas accumulations within the sandstone units. Some drilled well data, e.g., CB-1-SP and TI-1-SP, show hydrocarbon (gas) presence based on the typical resistivity and the combined neutron-density responses at depths up to 3400 m, indicating the possibility of other hydrocarbon members apart from the heavy oil (bitumen) observed from the near-surface rocks samples. From the three-dimensional (3-D) model, the free fluid indicator (FFI) is more significant towards the southwest and southeast of the area with deeper depths of occurrence, indicating portions with reasonable hydrocarbon recovery rates and good prospects for CO2 injection, circulation and permanent storage. However, future studies based on contemporary datasets are required to establish the hydrocarbon viability further, foster gas production events, and enhance CO2 storage possibilities within the region.