Development and evaluation of organic/metal ion double crosslinking polymer gel for anti-CO2 gas channeling in high temperature and low permeability reservoirs

Abstract

CO₂ flooding enhanced oil recovery (CO₂-EOR) represents a significant technology in the low permeability reservoir. With the fractures and heterogeneity in low permeability reservoirs, CO₂-EOR is susceptible to pessimistic gas channeling. Consequently, there is a need to develop conformance control materials that can be used in CO₂-EOR. Herein, to address the challenges of low strength and poor stability of polymer gel in high temperature and low permeability reservoirs, a new organic/metal ion composite crosslinking polymer gel (AR-Gel) is reported, which is formed by low hydrolysis and medium to high molecular weight polymer (CX-305), organic crosslinking agent (phenolic resin), and aluminium citrate (Al(III)). The crosslinking of Al(III) with carboxyl group and organic/metal ion double crosslinking can construct a more complex and stable polymer gel structure on the basis of traditional chemical crosslinking, to cope with the harsh conditions such as high temperature. The structure–activity relationship of AR-Gel was revealed by rheology behavior and micro-morphology. The applicability of AR-Gel in reservoir was investigated, as was its strength and stability in supercritical CO₂. The anti-gas channeling and enhanced oil recovery of AR-Gel were investigated using low permeability fractured cores, and the field process parameters were provided. The gel can be used to meet supercritical CO₂ reservoirs at 110 °C and 20,000 mg/L salinity, with long-term stability over 60 days. The plugging rate of AR-Gel for fractured core was 97%, with subsequent CO₂ flooding resulting in an enhanced oil recovery by 34.5%. AR-Gel can effectively control CO₂ gas channeling and enhanced oil recovery. It offers a new material with high strength and temperature resistance, which is particularly beneficial in the CO₂ flooding for the conformance control of oil field.