Effectiveness evaluation and field application of CO2-viscoelastic fluid synergistic flooding in low-permeability tight reservoirs
CO2 sweep efficiency and gas channeling are key factors restricting the effectiveness of CO2 flooding in low-permeability tight reservoirs. To address the technical issues of low sweep efficiency and gas susceptibility to channeling in CO2 flooding, a viscoelastic fluid system (CMS) was proposed to...
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| Format: | Article |
| Language: | Chinese |
| Published: |
Editorial Department of Petroleum Reservoir Evaluation and Development
2025-08-01
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| Series: | Youqicang pingjia yu kaifa |
| Subjects: | |
| Online Access: | https://red.magtech.org.cn/fileup/2095-1426/PDF/1752896007734-943440886.pdf |
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| Summary: | CO2 sweep efficiency and gas channeling are key factors restricting the effectiveness of CO2 flooding in low-permeability tight reservoirs. To address the technical issues of low sweep efficiency and gas susceptibility to channeling in CO2 flooding, a viscoelastic fluid system (CMS) was proposed to improve CO2 flooding in low-permeability tight reservoirs. A systematic study was conducted on the viscoelasticity, interfacial activity, injectivity, plugging performance, and oil displacement performance of CMS under oil reservoir conditions. The synergistic flooding performance of CO2-CMS was explored, and field trials were carried out. Experimental results demonstrated that at reservoir temperatures ranging from 30-80 ℃, CMS with a mass fraction of 0.5% showed certain viscoelasticity, with elasticity as the dominant characteristic, and both viscosity and elasticity decreased as temperature increased. At an oil reservoir temperature of 45 ℃, the viscosity of CMS was 3.27 mPa·s, and it exhibited strong elasticity. Furthermore, CMS could effectively reduce the oil-water interfacial tension to 2.68×10-2 mN/m. After core samples were immersed in the CO2-CMS system, the water-phase contact angle decreased to 8.75°, indicating enhanced hydrophilicity. The CO2-CMS system demonstrated good injectability in low-permeability tight cores, with smaller slug sizes yielding better injection performance. In long-core displacement experiments, using a 0.3 PV slug of CMS followed by CO2 flooding increased the recovery rate by up to 27.79%. In double-tube parallel core displacement experiments, alternating CMS and CO2 proved most effective, as it successfully sealed the high-permeability cores and mobilized low-permeability cores, resulting in a 26.28% increase in recovery. Field trial data from well groups indicated that after applying CMS, the overall liquid and oil production increased, and the CO2 volume fraction in gas-channeling wells significantly decreased. This research provides new technical insights and practical solutions for improving the efficiency of CO2 flooding in low-permeability tight reservoirs. |
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| ISSN: | 2095-1426 |