抗高温清洁CO2 泡沫压裂液在页岩气储层的应用

为了实现裂缝型、低压、低渗、强水敏、易水锁等特殊油气藏的高效开发，采用研发的多元共聚物、黏度增效剂、调节剂等和CO2 混配，得到一种抗高温清洁CO2 泡沫压裂液（BCF 压裂液）。对压裂液体系进行了综合性能测试，结果表明:BCF 泡沫压裂液抗温能力可达140 ℃，在90 ℃下泡沫液具有优良的携砂性能，其半衰期超过5 h，泡沫液滤失系数与胍胶冻胶相当， 并且压裂液破胶彻底，破胶液残渣含量低至1 mg/L、表面张力在24 mN/m 以下。BCF 压裂液体系在延长油田YY2 页岩气井得到了成功应用，加砂成功率100 %，求产后单井无阻气量达到1.0×105 m3/d，是邻井产量的3 倍。试验表明，该压裂液具有常规CO2 泡沫压裂液不可比拟的优点，对此类特殊油气藏的高效开发和储层保护具有重大意义。

Application of high temperature clean CO2 foam fracturing fluid in shale gas reservoirs

In order to efficiently develop special fractured oil/gas reservoirs with low pressure, low permeability, strong water sensitivity and easy water locking, the multipolymer, viscosity synergist, modifiers, etc. are hence mixed with CO2 to form a high temperature clean CO2 foam fracturing fluid (BCF fracturing fluid). Comprehensive performance test was conducted to the fracturing fluid system and the test result shows that BCF foam fracturing fluid is capable of resisting a temperature of up to 140 ℃, under 90 ℃, the foam has good sand-carrying performance. Its half-life period is over 5 h. The filtration coefficient of foam fluid is equivalent to that of guar gel. In addition, the gel breaking in fracturing fluid is complete, and gel breaking fluid has as low as 1 mg/L of residues and its surface tension is below 24 mN/m. BCF fracturing fluid system was successfully applied to YY2 shale gas well in Yanchang Oilfield. The sand adding successful rate was 100%, and the open gas production of single well after well flow was 1.0×105 m3/d, which was three times that of adjacent well. Tests indicate that this fracturing fluid has some advantages over conventional CO2 foam fracturing fluid and is of great significance to efficient development and protection of special oil/gas reservoirs.