A comprehensive review of hydrogel performance under CO2 conditions for conformance control

Abstract

Hydrogels with different compositions have been designed to improve CO2 sweep efficiency and to reduce excessive CO2 production by reducing reservoir heterogeneity. The hydrogels that have been applied in CO2 flooding can be classified into three major types: in-situ gel, foamed gel, and preformed particle gel. The polymerization of monomer gel happens in the reservoirs; however, the monomer gels were replaced by cost-effective polymer gels due to economic and environmental concerns. Conventional polymer gels include metallically crosslinked PAM gel, organically crosslinked PAM gel and biopolymer gel. The most commonly used polymer gel in the CO2 flooding fields is the HPAM/Cr(III) polymer gel. A variety of hydrogels were applied in the CO2 flooding fields; however, the field application results are mixed. In order to improve the hydrogel performance under the CO2 condition, some novel gels were developed in the laboratories. The primary purpose of this study is to review hydrogel performance under the CO2 condition and provide recommendations for future gel development for CO2 flooding.