Using propanol as an additive to CO2 for improving CO2 utilization and storage in oil reservoirs

Abstract

CO2 flooding has been recognized as one of the major alternatives for CO2 emission reduction and as well as increasing in the recovery from the oil reservoirs. However, CO2 is scrutinized for its potential low efficiency for oil recovery coupled with CO2 storage for various reasons, mainly miscibility requirements, character of the oil and as well as the reservoir heterogeneity related complications. Furthermore, heavier (viscous) oils will lead to additional complications in terms of efficiency. In this study, propanol is proposed as a novel cosolvent to improve CO2 for heavy oil recovery, while assisting CO2 storage in oil reservoirs. Influence of propanol on the solubility of CO2 in heavy oil is first investigated to reveal the mechanism of propanol in assisting CO2 for oil viscosity reduction. Performance of propanol assisted CO2 flooding is then compared with that of propane assisted CO2 flooding to validate the potential of propanol as an additive to CO2 for heavy oil recovery while assisting CO2 storage in oil reservoirs. Results show that propanol results in the largest decrease in the viscosity of oil-phase by more than 50% compared to pure CO2 and propane by improving CO2 solubility in the oil-phase. Propanol assisted CO2 flooding has better performance in recovering heavy oil from the medium-permeability cores by more than 19% than propane assisted CO2 flooding, especially from the smaller pores. In addition, the flowback ratio is as high as 95% for propanol, suggesting that propanol can be used as a clean additive to CO2 for reservoir development. More importantly, compared to propane, propanol favors up to 13 % more CO2 storage in oil reservoirs, suggesting that propanol is also a suitable agent for assisting CO2 sequestration.