Assessment of CO2 storage capacity in oil reservoirs associated with large lateral/underlying aquifers: Case studies from China

Abstract

CO2 injection into oil and gas reservoirs associated with large aquifers takes advantages of lower geological leakage risk associated with oil and gas traps, and large storage capacity of their connected aquifers. The storage capacity in such combined reservoirs can be assessed by a material balance method which considers different trapping states of CO2 in oil reservoirs and aquifers. Case studies of five oil reservoirs selected from Shengli and Jiangsu oilfields in China are conducted and the results show that CO2 storage capacity can be greatly increased if the lateral and underlying aquifers are included. Oil and water displacement and CO2 dissolution in remaining oil are the main forms of CO2 trapping in oil reservoirs, while CO2 gas trapping and dissolution in saline water are the main mechanisms for CO2 storage in associated aquifers. CO2 injection into combined reservoirs can be a favorable option for the oil industry in the near future, and the potentials of CO2 EOR and storage deserve further detailed studies.