Techno-economic analysis of intermediate hydrocarbon injection on coupled CO₂ storage and enhanced oil recovery

This study proposes economic evaluation of CO₂ geological storage with enhanced oil recovery. The procedures consider capital expenditures and operating costs of infrastructures and revenues from oil recovery and carbon tax credits. Extensive CO₂ geological storage with enhanced oil recovery simulations was conducted to determine the most promising scenario among cases, where miscibility was controlled by the addition of liquefied petroleum gas. The addition of liquefied petroleum gas into a CO₂ injection stream can accelerate reduction of oil viscosity, interfacial tension, and oil density, which cause improved displacement efficiency. The larger was the amount of liquefied petroleum gas injected, the greater was the miscibility due to minimum miscibility pressure reduction, resulting in higher oil recovery and less CO₂ sequestration. Although liquefied petroleum gas addition enhances the performance of CO₂ enhanced oil recovery, economic analysis should be conducted for CO₂ geological storage with enhanced oil recovery due to the higher price of liquefied petroleum gas than that of CO₂. Net present value decreased from liquefied petroleum gas mole fraction of 0–2% and started to increase from mole fraction 2–13% due to the miscibility effect. Then, net present value started to decrease, because the purchasing and injecting prices of the required liquefied petroleum gas exceeded that of the oil produced. Economic evaluation showed that addition of 13% liquefied petroleum gas was the most promising scenario, with a net present value of 91 MM$. Thus, we confirmed an optimum liquefied petroleum gas concentration in the CO₂ geological storage with enhanced oil recovery process.