压裂多级裂缝内动态输砂物理模拟实验研究

为了研究压裂过程中裂缝内支撑剂的动态输砂规律及分布形态，采用自主研制的多尺度裂缝系统有效输砂大型物理模拟实验装置，进行了压裂液黏度、支撑剂类型、注入排量和砂比等对支撑剂在不同尺寸裂缝中的动态输送和砂堤剖面高度影响的模拟实验。实验结果表明，裂缝内动态输砂规律的影响因素，按影响程度从大到小依次为压裂液黏度、支撑剂粒径、砂比和排量；压裂液黏度越高，沉砂量越少，砂堤剖面高度越小而平缓，且在主裂缝中更为明显；支撑剂粒径越大，沉砂量越多，砂堤剖面高度越大，且在主裂缝中更加明显；砂比越高，沉砂量越大，砂堤剖面高度也越大，且在分支缝中增幅更大；随排量增大，主裂缝中的沉砂量略减小，分支缝中的沉砂量差别不大。研究结果为优选压裂液、支撑剂，制定压裂方案，以及优化压裂施工参数提供了理论依据。 

Experimental Study on the Physical Simulation of Dynamic Sand Transport in Multi-Stage Fractures

To study the dynamic sand transportation and distribution patterns of proppant within fractures during hydraulic fracturing, an experimental device simulating sand transport in fracture systems with multi-scale was self-developed. This included carrying out an experimental study on dynamic sand transportation law and proppant height distribution patterns within fractures of different sizes under different frac fluid viscosity, proppant type, pumping flow rate and proppant concentration. The experimental results showed that the viscosity of frac fluid is the most influential factor followed by particle size of the proppant, proppant concentration and flow rate. The higher the viscosity of fracturing fluid, the less proppant settlement, and the lower and the gentler the settled proppant bank profile. This is more obvious in main fractures. The larger the particle size of the proppant, the more the settled proppant, the higher the settled proppant bank profile. It is more obvious in main fractures, too. Similarly, the higher the proppant concentration, the more the settled proppant, and the higher the settled proppant bank profile. This change is even more notable in branched fractures. The higher the flow rate, the slightly less the settled proppant. Further, it is almost the same in branched fractures. The research results will provide a theoretical basis for the optimization of frac fluid, proppant, and fracturing operation parameters as well as a formulating fracturing scheme.