State of the Art for Conformance Control in CO2 EOR: A Comprehensive Review of Research and Field Applications Related to Gel Remediating Bypassed Zone

It was estimated that the implementation of Carbon Dioxide-Enhanced Oil Recovery (CO2-EOR) contributed to reducing 10-20 billion tons of Greenhouse Gas (GHG) emission in U.S. As a significant Carbon Capture and Storage (CCS) technologies, CO2-EOR possessed enormous industrial value with its 40 years of commercial operational experience. The increasing number of miscible and immiscible CO2 projects reflected industry’s growing interest for CO2-EOR. It was reported that the number of miscible CO2 projects boosted to 127 from 103 projects in 2010, holding the maximum EOR practice in U.S.

There are several reasons accounting for this tendency. Besides its positive role in utilizing anthropogenic carbon, CO2-EOR also featured low-cost, high-efficiency, and widely applicable. In spite of its versatility, the incremental oil recovery of CO2-EOR is still impeded, owing to the gas mobility, channeling problem and reservoir heterogeneity, dispersion (mixing) and gravity effects. Unfavorable mobility of gas will result in an early breakthrough, therein lead to a poor volumetric sweep. Moreover, the existence of fractures, channels or high-permeability streaks in reservoir can significantly exacerbate the deficiency of CO2 flooding.

To remedy above problems and furtherly improve recovery efficiency of CO2 flooding, a new concept termed of “Next Generation CO2-EOR” was proposed. Accordingly, four general technology development areas involved in “Next Generation CO2-EOR”. They are Mobility Control Enhancement; Improved Flood Conformance; Monitoring Technology Enhancement; Planning and Evaluation Enhancement . Among these, how to improve the flood conformance was a challenging but achievable topic, thus a large number of efforts were conducted. This paper tried to give a serious and comprehensive review of both laboratory experiments and field applications related to conformance improvement in CO2-EOR.