Effective Pore-Throat Sweep Limits and Microscopic Oil Mobilization during CO_(2)-WAG Flooding in Low-Permeability Conglomerate ReservoirsOA
Low-permeability conglomerate reservoirs are characterized by complex pore structures and poor sweep efficiency,making the optimization of carbon dioxide-water alternating gas(CO_(2)-WAG)injection critical for enhanced oil recovery.To evaluate the displacement performance of CO_(2)-WAG and determine the lower limit of effectively swept pore throats,this study presents long-core flooding experiments conducted on cores from the KS Formation of the B Oilfield in the Junggar Basin under reservoir conditions(20.1 MPa and 58℃).Continuous CO_(2) flooding and CO_(2)-WAG schemes with varying cycle numbers and gas-water ratios(GWRs)were systematically compared.In situ online nuclear magnetic resonance(NMR)monitoring was employed to quantitatively characterize the mobilization of microscopic remaining oil during flooding.The results demonstrate that CO_(2)-WAG significantly outperforms continuous CO_(2) flooding.Among the tested scenarios,three alternating cycles and a GWR of 1:1 yielded the highest oil displacement efficiencies of 64.8% and 66.13%,respectively,representing improvements of 23.6% and 24.53% over water flooding and 4.75% and 6.08% over continuous CO_(2) flooding.NMR analysis revealed that water flooding primarily mobilizes crude oil in larger pore throats,with an effective sweep limit of approximately 18.2 nm.In contrast,CO_(2)-WAG extends the lower limit of effectively swept pore throats to 9.52 nm,enabling the recovery of oil trapped within mesopores and micro/nano-scale pore systems.Mechanistically,the injected water slugs improve sweep efficiency and suppress gas channeling,while the CO_(2) slugs reduce crude oil viscosity and enhance displacement within smaller pores.This synergistic combination of macroscopic sweep improvement and microscopic displacement enhancement substantially increases oil recovery.
Xiaoguang Wang;Dehua Liu;Zhenping Liu;Zhen Luo;Guihua Yang;Zongfa Li;Lijuan Huang
State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization(Yangtze University),Wuhan,China School of Petroleum Engineering,Yangtze University,Wuhan,ChinaState Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization(Yangtze University),Wuhan,China School of Petroleum Engineering,Yangtze University,Wuhan,ChinaResearch Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay,ChinaResearch Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay,ChinaState Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization(Yangtze University),Wuhan,China School of Petroleum Engineering,Yangtze University,Wuhan,ChinaState Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization(Yangtze University),Wuhan,China School of Petroleum Engineering,Yangtze University,Wuhan,ChinaState Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization(Yangtze University),Wuhan,China School of Petroleum Engineering,Yangtze University,Wuhan,China
能源科技
CO_(2)-WAGconglomerate reservoirsoil displacement efficiencynuclear magnetic resonanceproducing limit
《Fluid Dynamics & Materials Processing》 2026 (7)
P.22-43,22
Technology Integration and Demonstration of CO_(2) Miscible Flooding 609 in Water-Sensitive Low-Permeability Conglomerate Reservoirs(2025ZD1408403)Research on the Demonstration Project of the“Ballast Stone”in BaiKouQuan/WuXia Oilfields,a Science and Technology Project of the Oil and Gas and New Energy Branch of China National Petroleum Corporation(2023YQX10207)(Xiaoguang Wang)the Xinjiang“Tianshan Talent”Training Program(2022TSYCCX0050)(Xiaoguang Wang)Special Project of Xinjiang Oilfield Company on“Research and Field Test of Geological Reservoir Engineering for CO_(2) Flooding in Junggar Basin”(2024XJZX0801)(Xiaoguang Wang)the Natural Science Foundation of China(NSFC)(Grant No.52504021)(Zongfa Li).
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