Numerical simulation on fracturing fluid flowback from post-fracturing shale gas wells and influencing factors

Abstract Fracture network fracturing is a key technology to achieve economic and effective development of shale gas. The flowback data after hydraulic fracturing is crucial to the characterization of hydraulic fracture networks and reservoir evaluation. Based on the flowback characteristics of shale gas fracturing fluid, combined with the crossflow equation and the flow material balance equation, a tree-shaped fractal fracture network two-phase flowback model is established in this paper suitable for inverting the effective fracture network volume of shale gas, which is used to calculate the effective fracture network volume and conduct sensitivity analysis of the main flowback parameters. The reliability of the model is verified by the actual flowback data of field fracturing wells. The research shows that the larger the initial fracture width of the tree-shaped fractal fracture network, the larger the peak value of the water, the larger the double peak value of the gas production curve, and the higher the flowback rate; the larger the ratio of fracture order to fracture length, the lower the flowback rate; the larger the ratio of fracture width to fracture height, the higher the flowback rate. By optimizing the fracture network structure, the flowback rate and test production of shale gas wells with fracture network fracturing can be improved. The flowback law of shale gas can be studied effectively by the tree-shaped fractal fracture network two-phase flowback model. And it has important value for the optimization design of shale gas fracturing.