煤层气水力压裂缝内变密度支撑剂运移规律

针对煤层气水力压裂有效支撑缝长过短且缝内铺砂浓度分布不均匀的问题,研究变密度支撑剂颗粒在裂缝内的运移规律。采用Pseudo Fluid模型考虑了裂缝内支撑剂颗粒之间的相互影响,借助Visual Studio 2012设计平台编制相应计算软件,并通过与现场监测值进行对比,校核了软件计算的准确性。讨论了压裂液黏度、裂缝壁面、排量和支撑剂密度等参数对缝内铺砂浓度和有效支撑缝长影响规律,分析了超低密度支撑剂在不同围压和温度工况下的破碎率。结果表明:坚果壳支撑剂在围压为69 MPa、环境温度为90℃工况下破碎率2%,满足现场需求;随着压裂液黏度、施工排量增加,裂缝支撑长度增加,缝内铺砂更加均匀;支撑剂颗粒直径增加使得裂缝支撑长度降低;采用变密度支撑剂较单一陶粒砂有效支撑半缝长增加了19.5 m,且铺砂效果更均匀。

Variable density proppant placement in CBM wells fractures

The migration law in the cracks of variable density proppant particles had been researched，for effective support fracture length of CBM hydraulic fracturing was too short and seam sanding concentration distributed uneven.The mutual influence of the fracture proppant particles was considered using Pseudo Fluid model，and the corresponding calculation software was written with the Visual Studio 2012 design platform，then the accuracy of the calculations was checked through comparison with the value of field monitoring software.The effective law to seam sanding concentration and effective support slot length of the fracturing fluid viscosity，wall cracks，displacement and proppant density parameters were discussed，and the broken rate of the ultra low density proppant was analyzed at different confining pressure and temperature conditions.The results show that broken rate of a nut shell proppant is less than 2% in the condition of confining pressure 69 MPa and the ambient temperature 90 ℃，which meet the site requirements；With the increase of fracturing fluid viscosity，the construction displacement and fracture bracing length，the seam sanding is more uniform；with the proppant particle diameter increases，the crack support length decreases；compared to single ceramic sand，using variable density proppant makes effective support half slot length increasing 19.5 m，and the sanding effect is more uniform.