Numerical simulation of proppant migration and settlement behavior in complex smooth fractures

ABSTRACT: Hydraulic fracturing is a key technology to realize the commercial development of unconventional oil and gas resources, and the migration and settlement effects of proppant in complex fractures directly determine the quality of fracture conductivity.In order to clarify the migration characteristics of proppant in fractures, this paper first analyzes the force and settlement mechanism of proppant particles, and then uses computational fluid dynamics (CFD) software to simulate the influence of injection velocity and fluid viscosity on the migration and laying of proppant in complex fractures, so as to determine the optimal construction parameters under the two key influencing factors.The results show that: (1) Different factors have a reasonable value range, and values exceeding this range will lead to poor paving effect.The influence of the research parameters on the area of fractured sand embankments at all levels showed a gradual weakening trend.The rule is that the main fracture has the greatest influence and the third fracture has the least impact.(2) The injection speed (0.3~0.7m/s) is proportional to the drag force of the sand carrying liquid, and the use of higher injection speed will increase the migration distance of the proppant in the main fracture, so increasing the injection speed appropriately will promote the expansion and extension of the fracture.(3) The viscosity of the fracturing fluid (3~7mPa-s) is inversely proportional to the sedimentation velocity of the proppant particles, and the increase of viscosity increases the buoyancy and viscous force of the fluid to the particles, resulting in the outflow of proppant at the outlet end and the balance height of the fracture decreases.(4) In the actual construction process, the parameters(such as fracturing fluid viscosity, injection rate and proppant ratio) can be adjusted in real-time according to the relationship curve between construction displacement and pressure, so as to promote the uniform laying of proppant in fractures at all levels and improve the conductivity of fractures and the production of oil and gas wells.