Abstract
Carbonate rocks have become very important in Brazil with pre-salt reservoir discoveries in Santos and Campos Basins. Since then, great efforts in research and technology have been made to characterize and develop these reservoirs. In this sense, outcrop analogue studies have become a powerful tool for helping the recognition of geological heterogeneities responsible for controlling the fluid flow in hydrocarbon reservoirs. Besides that, pre-salt oil recovery is associated with high carbon dioxide (CO2) production, and due environmental issues, it is required a sustainable destination for this contaminant. CO2 injection in the reservoir, either pure or mixed to the produced gas stream, could be a good manner to deal with this undesirable component and increase the oil recovery. This work uses outcrop analogue characterization to understand how carbonate reservoir characteristics impact the selection of the best recovery strategy under Brazilian-pre-salt-like conditions. Numerical simulation models were run using the flow simulator TEMPEST MORE (version 7.1) with isothermal compositional modeling. The oil recovery process was modeled by continuous and alternating injection of CO2 and water. The recovered oil fractions for the simulation case with water alternating CO2 injection were higher than with the use of continuous injection of CO2 or water.
Highlights
In Brazil, carbonate rocks have become very important since giant pre-salt reservoirs discovered in Santos and Campos Basins
Pre-salt oil recovery is associated with high carbon dioxide ( CO2) production, and due to environmental issues, it is required a sustainable destination for this contaminant. CO2 injection is an enhanced oil recovery process that has become a trend in order to avoid the emission of this gas into atmosphere and to increase oil recovery
The results showed that CO2 injection increased microscopic displacement efficiency because the residual oil after C O2 flooding was lower than the residual oil after water flooding. CO2 flooding from the beginning of the production lowers the remaining oil saturation in the reservoir and could be a good alternative for the exploitation of pre-salt reservoirs due to the availability of this gas, once oil recovery is associated with high CO2 production, and due environmental issues
Summary
In Brazil, carbonate rocks have become very important since giant pre-salt reservoirs discovered in Santos and Campos Basins. Great efforts in research and technology have been made to characterize and develop these reservoirs, such as analogue outcrop studies. It is important to note that diagenetic differences between the reservoir and the analogue outcrop must be respected (Aderaldo 1994; Gauw 2007). Carbonate rocks form most oil reservoirs in the world, the knowledge about these reservoirs is still low if compared to siliciclastic reservoirs. Due to their more prominent reactive nature, carbonate rocks usually suffer a more intense chemical diagenesis, resulting in more heterogeneous pore systems. As regards wettability, carbonates tend to range from neutral to oil-wet, which may affect multi-phase displacement and capillary behavior of the porous medium (Pizarro and Branco 2012)
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