水力压裂过程中陶粒支撑剂运移规律及粒级配比优化

Migration law of ceramsite proppant and its granularity matching during coalbed methane fracturing

对比了传统石英砂与陶粒支撑剂在压裂过程中的运移情况,认为石英砂压裂产生的砂堤和悬砂区范围明显小于陶粒支撑剂,且造缝能力弱于陶粒;之后,采用物理实验与数值模拟相结合的方法研究了沁水盆地高河地区煤层气井QS01井在压裂过程中陶粒的运移规律及粒径配比。结果表明:在闭合压力相同时,大粒径陶粒的导流能力强于小粒径陶粒;大粒径陶粒随闭合压力增加导流能力下降速度变慢,说明大粒径陶粒在高闭合压力下仍得到了有效的支撑;250~380μm,380~1 000μm和830~1 400μm的陶粒配比为1∶6∶2时,平均支撑剂浓度最大,裂缝导流能力最高;粒径配比为3∶1∶2时,压裂裂缝长度与支撑缝长最大,导流能力最低;粒径配比为1∶1∶1时的压裂效果基本介于其它2种配比效果之间。因此,压裂过程中陶粒粒径配比建议选择1∶6∶2(250~380μm∶380~1 000μm∶830~1 400μm)。

Migration abilities of conventional quartz sand and ceramsite proppant are compared. Results show that area of sand dike and suspended sand for quartz sand is both smaller than that of ceramsite, and the width generation capacity of quartz sand is weaker than that of ceramsite. Then, a typical coalbed mehane well named QS01 well located at Gaohe block of Qinshui Basin is selected as the simulation object, and physical experiments and mathematical simulations are both conducted to obtain the migration feature of ceramsite proppant and its granularity matching. Results show that under the same closure pressure, the fracture conductivity of bigger size is greater than that of smaller size;for bigger size ceramsite, the decrease rate will be reduced as closure pressure increasing, which indicates that the bigger size ceramsite has been effectively supported under bigger closure pressure. If the granularity matching of 250-380 μm, 380-1 000 μm and 830-1 400 μm is 1∶6∶2, the proppant concentration is the biggest, and the fracture conductivity is the strongest. If the granularity matching is 3∶1∶2, the proppant concentration is the smallest, and the fracture conductivity is the weakest. And if the granularity matching is 1∶1∶1, the values of proppant concentration and fracture conductivity are among the values of the two conditions above. As a result, the granularity matching should set as 1∶6∶2 during fracturing.