Study on Physical Simulation Experiment of Dynamic Sand Transportation in Complex Fractures

The transportation law and distribution form of proppant are the important factors affecting the fracturing effect. In order to study the dynamic sand transportation law in the process of fracturing, an experimental device that simulate the effective sand transportation in multi-scale fracture system was developed. Under the condition of simulating main fracture, primary branch fracture and secondary branch fracture, the experiments that study the effects of different fracturing fluid viscosity, proppant type, injection flow rate, sand ratio and other factors on the dynamic sand transportation law and sand dike distribution pattern were carried out. The experimental results showed that the flow proportion in all stages of fractures decreased stage by stage, the average proportion of main fractures was 64.6%, while the average proportion of primary branch fractures was 22.2%, and the average proportion of secondary branch fractures was 13.2%. The flow distribution proportion in the fractures was mainly affected by the total flow, the larger the flow was, the higher the flow proportion in the main fractures was, and the lower the flow proportion in the branch fractures was. The influencing factors of sand dike distribution were the viscosity of fracturing fluid, particle size of proppant, sand ratio and displacement from lager to small. The higher the viscosity of fracturing fluid was, the less sand deposited, the lower the sand dike profile was. The larger the particle size of proppant, the more sand deposited, the higher the sand dike profile was. The higher the sand ratio, the more sand deposited, the higher the sand dike profile was. The higher the displacement, the less sand deposited, and the lower the sand dike profile was, but difference was quite small. The research results enrich the evaluation method of dynamic sand transportation law in multi-stage fractures, and provide the basis for the optimization of fracturing fluid, proppant and fracturing construction parameters.