Comparison of different methods for determining key parameters affecting CO2 storage capacity in oil reservoirs

Abstract

Storing CO2 in oil reservoirs is not only an effective method for reducing CO2 emissions and greenhouse effects, but also a means to be more economical by enhancing oil recovery. The evaluation of CO2 storage capacity in oil reservoirs which is very important for the implementation of CO2 storage includes the evaluation of theoretical, effective, practical and matched storage capacities. Based on the volumetric balance theory, considering CO2 dissolved in remaining oil and water, sweep efficiency and displacement efficiency, this paper utilizes three methods to calculate theoretical and effective CO2 storage capacity in oil reservoirs, in which CO2 volumetric sweep efficiency, oil recovery factor and sequestration factor are key parameters. This work presents a reservoir numerical simulation method, an empirical formula method, and a stepwise regression method. The feasibility, superiority and limitations of the methods for calculating these three key parameters and storage capacities – including theoretical and actual CO2 storage capacities – were analyzed through simulated applications in three reservoirs of the Xinjiang Oilfield of China. The results indicated that the assessment results of stepwise regression has a high level of accuracy, and that this oilfield can provide a large storage capacity and is thereby worthy of further study.