Case Study of CO2-IGR and Storage in a Nearly Depleted Gas-condensate Reservoir in Taiwan

Abstract

The purpose of this modelling study is to investigate the combined contributions of CO 2 -IGR and CO 2 storage in a nearly depleted gas-condensate reservoir, Taiwan. The estimation of the storage potential of a depleted gas condensate reservoir, the evaluation of the economic benefits from the CO 2 -improved gas recover (IGR), and the determination of the best operating strategy for maximizing economic benefits were studied. After the CO 2 mixed with the natural gas, the two-phase envelope shrinkage was noticed in the Pressure-Temperature (P-T) diagram for CO 2 -IGR phase in the reservoir. The mechanisms of CO 2 displacement and condensate revaporization contributed to the gas recovery. Due to the gravity, the stored CO 2 sank to the bottom of the gas cap; consequently, and the injected CO 2 can be stored permanently. The best economic scenario for this case study, which had the highest net present value (NPV) of US $18.7 million, was to use one down-dip injection well with an injection rate of 30,000 standard cubic meters (SCM)/day and a discount rate of 10%. The analysis of the principal components of the economic assessment showed that the benefit of CO 2 -IGR was highly sensitive to the cost of CO 2 capture, and that the carbon tax incentive had a positive effect on the economic benefit of the Carbon Capture, Utilization, and Storage (CCUS) method.