Experimental investigation on conformance control and EOR-CO2 sequestration of non-chemical CO2 microbubbles in low permeability reservoirs

The non-chemical CO2 microbubble (MB) technology has drawn widespread interest owing to its excellent conformance control and environmental sustainability. Although extensive studies have been conducted on MB's conformance control, the adaptive relationship between microbubble diameter and core pore diameter remains unclear. In this paper, it is the first time to investigate systematically the adaptive relationship by conformance control experiment, revealing an optimal microbubble pore adaption coefficient (MPAC) of 1.55. Then, the impacts of gas-liquid ratio and injection rate on MB's conformance control performance were analyzed, and a sensitivity analysis and comparison of the sensitivity index were performed. Finally, the enhanced oil recovery (EOR) performance and carbon sequestration capability (CSC) were evaluated. Experimental results indicated that the optimal gas-liquid ratio and injection rate are 1:1 and 0.10 mL/min, respectively. The core flooding experiment demonstrated that MB exhibits superior EOR and CSC compared to water-alternating gas (WAG) and continuous CO2 flooding, achieving incremental oil recovery of 24.21 %, 18.63 %, and 10.52 % of original oil in place (OOIP) based water flooding (WF), with corresponding CSC of 54.61 %, 48.52 %, and 38.48 %, respectively. Overall, this study provided valuable insights for optimizing MB's practical application and demonstrated that CO2 MB is an effective EOR along with carbon sequestration method in low permeability reservoirs.