裂缝扩展与支撑剂运移动态耦合是目前水力压裂数值模拟技术面临的挑战之一。为了探究页岩动态裂缝缝内支撑剂铺置特征,基于三维离散元方法,建立考虑层理的页岩储层裂缝扩展与支撑剂运移动态耦合数值模型,分析了不同支撑剂粒径、支撑剂密度、压裂液黏度和支撑剂注入方式下的裂缝扩展与支撑剂铺置规律。研究表明:粒径越小,支撑剂铺置范围越广,铺置越均匀,粒径为150 μm的支撑剂的铺置面积与铺置效率是粒径为600 μm的支撑剂的1.8倍;支撑剂密度不是影响裂缝扩展和支撑剂运移的主要因素;压裂液黏度越高,裂缝面积和铺置面积越小,铺置效率越高,黏度从1 mPa·s增至15 mPa·s,裂缝面积减少45%,铺置面积减少34%,铺置效率增大12%;支撑剂注入方式为阶梯注入时,压裂液造缝与携砂效果最好。该研究成果可为页岩储层有效改造提供理论指导。
The dynamic coupling of fracture propagation and proppant migration is one of the challenges in terms of hydraulic fracturing numerical simulation technology. In order to investigate the characteristics of proppant placement in shale dynamic fractures, based on the three-dimensional discrete element method, a dynamic coupling numerical model of fracture propagation and proppant migration in shale reservoirs considering bedding was established, and the laws of fracture propagation and proppant placement under different proppant particle sizes, proppant density, fracturing fluid viscosity and proppant injection methods were analyzed. The study shows that: The smaller the particle size, the wider the proppant placement range and the more uniform placement.The placement area and placement efficiency of the proppant with a particle size of 150 μm are 1.8 times that of the proppant with a particle size of 600 μm; the proppant density was not the main factor affecting fracture propagation and proppant migration; the higher the viscosity of fracturing fluid, the smaller the fracture area and placement area, and the higher placement efficiency, the viscosity increased from 1 mPa·s to 15 mPa·s, and the fracture area decreased by 45%, and the placement area reduced by 34%, and the placement efficiency increased by 12%.When the proppant injection method is step injection, the fracturing fluid has the best effect on fracture creation and sand carrying. The study results can provide theoretical guidance for effective modification of shale reservoirs.
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