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沁水盆地高阶煤储层采用活性水压裂工艺后,直井平均单井日产量仅1 000 m3/d左右。理论分析和压裂监测统计表明,常规活性水压裂工艺存在压裂容易窜层和活性水携砂能力差、支撑距离短的弊端,制约了煤层的改造效果和单井产量的提升。为进一步提高煤层气井压裂改造效率,利用低黏液体携砂能力差、易形成砂堤的特性,提出煤层多次铺砂压裂工艺思路。以裂缝和砂堤为研究对象,根据物质平衡理论,建立了活性水多次铺砂压裂数学模型,同时优化压裂排量、液量和支撑剂粒径等工艺参数。现场试验结果表明,应用三次铺砂压裂工艺大大降低了煤层压窜的程度,压后单井平均日产气量达到2 223 m3/d,验证了三次铺砂数值计算模型指导现场施工的可行性。
After the activated water fracturing process is applied to the high-rank coal reservoirs in Qinshui Basin, the average single-well daily output of straight wells is only about 1 000 m3 / d. Theoretical analysis and fracturing monitoring statistics show that the conventional active water fracturing technology has the disadvantages of easy channeling by fracturing and poor carrying capacity of activated water and short supporting distance, which restricts the effect of coal seam reforming and single well production increase. In order to further improve the efficiency of fracturing in coalbed methane wells, the sandblasting characteristics of poor sand carrying capacity with low viscous liquid and easy formation of sandbanks are proposed. Taking fractures and sand banks as the research object, according to the material balance theory, a mathematical model of multiple sand-blasting of active water was established, and the process parameters of fracturing displacement, fluid volume and proppant particle size were optimized. The field test results show that the application of three times of sand fracturing process greatly reduces the degree of coal stratification and channeling. The average daily gas production of single well reached 2,223 m3 / d after pressurization, verifying the feasibility of three times of sand numerical calculation model guiding on-site construction.