A Study on the Migration Rule and Flow Conductivity of Multi-particle Size Proppant in Shale Reservoir

Abstract

To solve the problem that it is difficult to realize efficient prop of fracture network system in the volume fracturing process of shale reservoir, the migration and settlement mechanism of proppant in fractures is analyzed, the migration law of proppant under different particle size and different combination conditions is studied by using true three-dimensional simulation software, and the distribution of proppant concentration and fracture conductivity are simulated. On this basis, the applicability of proppant with different particle sizes under different fracture morphology is judged, and the combination of proppant particle sizes is optimized to maximize the full prop of the fracture network system, improve the conductivity of the fracture network system, and realize efficient fracturing stimulation of shale reservoirs. The research shows that when the fracture width is very small and the average fracture width is less than 1mm, it is difficult for medium/large size proppant to enter the fracture network and achieve effective fracturing prop. Therefore, it is recommended to use small/micro size proppant. Under the condition that the average fracture width is greater than 1mm and the proppant with large particle size can effectively enter the fracture, the combination of large size + medium size proppant particles settle quickly, and the porosity of the sand dike is large, which can reach a larger equilibrium height, increase the effective support width of the fracture, and improve the conductivity of the fracture network. The fracture conductivity is not only related to the proppant placement concentration, but also depends on the proppant placement structure in the fracture. After the fracture is effectively propped, further increasing the proppant concentration will block the fracture system and reduce the conductivity. Therefore, it is not suitable to pump small size proppant after pumping large/medium size proppant, so as to avoid unnecessary plugging to the proppant. Small size proppant is suitable for use in the early pumping phase.