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Optimization and performance evaluation of a novel anhydrous CO2 fracturing fluid
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2022-08-02 , DOI: 10.1016/j.jngse.2022.104726
Mingwei Zhao , Shichun Liu , Yang Li , Zhiyuan Liu , Yining Wu , Xin Huang , Ruoqin Yan , Caili Dai

The conventional water-based fracturing fluids have such defects as large water consumption, serious environmental pollution and water-sensitive damage to reservoirs in the development of tight oil. In this study, a novel anhydrous CO2 fracturing fluid system was constructed with the compositions of 7 wt% polydimethylsiloxane (100 cs), 5 wt% ethanol and 88 wt% liquid CO2. The viscosity of the system could reach 6.52 mPa s, which was 37 times higher than that of pure liquid CO2 at −15 °C and 30 MPa. The pressure resistance, temperature resistance, anti-swelling property, filtration loss property, core damage property, corrosion property and wetting inversion property of anhydrous CO2 fracturing fluid were systematically evaluated by physical simulation experiments. The environmental scanning electron microscopy (ESEM) and mercury injection experiment were conducted. The viscosity retention rate of anhydrous CO2 fracturing fluid reaches 47.92% when the temperature increases by 50 °C. When the pressure increases by 25 MPa, the viscosity increases by 2.6 times. It ensures that the viscosity of anhydrous CO2 fracturing fluid is well retained after injection into the formation. In addition, the anti-swelling rate of anhydrous CO2 fracturing fluid reaches 90.91%. The filtration coefficient is reduced by 69.20%. For low permeability sandstone cores, the permeability damage rate is 18.80% and the porosity damage rate is 12.58%. After aging for 30 h, the permeability and porosity of core increased 39.23% and 5.52%, respectively. Meanwhile, the wettability of the core could be changed from hydrophilic to neutral, which reduced the flow resistance of the oil phase and improved tight oil recovery. Through this study, we hope to broaden the application of anhydrous CO2 fracturing fluids in tight oil development.



中文翻译:

新型无水CO2压裂液的优化与性能评价

常规水基压裂液在致密油开发过程中存在耗水量大、环境污染严重、储层水敏性破坏等缺陷。本研究构建了一种新型无水CO 2压裂液体系,其组成为7 wt%的聚二甲基硅氧烷(100 cs)、5 wt%的乙醇和88 wt%的液态CO 2。该体系的粘度可以达到6.52 mPa s,比纯液态CO 2在-15 ℃和30 MPa下的粘度高37倍。无水CO 2的耐压性、耐温性、抗膨胀性、滤失性、芯损性、腐蚀性和润湿反转性通过物理模拟实验对压裂液进行了系统评价。进行了环境扫描电子显微镜(ESEM)和汞注入实验。温度每升高50℃ ,无水CO 2压裂液的粘度保持率达到47.92%。当压力增加25 MPa时,粘度增加2.6倍。它确保了无水CO 2压裂液在注入地层后的粘度得到很好的保持。此外,无水CO 2压裂液的抗溶胀率达到90.91%。过滤系数降低69.20%。适用于低渗透砂岩岩心,渗透率破坏率为18.80%,孔隙度破坏率为12.58%。老化30 h后,岩心渗透率和孔隙度分别增加了39.23%和5.52%。同时,岩心的润湿性可以从亲水性变为中性,从而降低油相的流动阻力,提高致密油采收率。希望通过本研究拓宽无水CO 2压裂液在致密油开发中的应用。

更新日期:2022-08-02
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