Improvement of Mobility and Conformance for CO2-EOR, a Review of Technologies and Application Conducted in China

Carbon Dioxide-Enhanced Oil Recovery (CO2-EOR), as a significant Carbon Capture and Storage (CCS) technology, exhibited enormous industrial value upon its 40 years of commercial operation. Nowadays, CO2-EOR is attracting a growing interest from both industry and academia. In accordance to the statistics reported by Al Adasani and Bai, more than 169 CO2-EOR projects have been conducted throughout the world. In China, both miscible and immiscible CO2 flooding have been implemented in Yanchang Jnlin, Daqing, Jidong, Jiangsu, and Shengli Oilfields. It was estimated that taking advantage of CO2-EOR technology, approximate 1.1 billion tons of incremental oil can be recovered from the onshore oilfields across China.

Besides its positive role in utilizing anthropogenic carbon, CO2-EOR also featured low-cost, high-efficiency, and widely applicable. The phase behavior and displacing mechanism greatly supported technique advantages. It is prone to reaching miscibility at 1500-3000 psi while nitrogen and hydrocarbon gases are holding much higher Minimum Miscible Pressure (MMP). In spite of its versatility, the sweep efficiency and reservoir conformance of CO2-EOR were still impeded due to the gas mobility, channeling problem and reservoir heterogeneity, dispersion (mixing) and gravity effects. In order to remedy these problems and furtherly improve the recovery efficiency of CO2 flooding, a new concept termed of “Next Generation CO2-EOR” was proposed. In detailed, four general technology development areas are involved in “Next Generation CO2-EOR”. They are Mobility Control Enhancement; Improved Flood Conformance; Monitoring Technology Enhancement; Planning and Evaluation Enhancement. Among these, Mobility Control Enhancement and How to improve the flood conformance were challenging but achievable topics, thus substantial work have been devoted.

As a review of “Next Generation CO2-EOR” practiced in China, we tried to give a serious and comprehensive review of both laboratory experiments and field applications regarding the efforts towards an improvement of mobility and conformance for CO2-EOR in this work.