Coupling Simulation Model of Transient Flow in Tubing and Unsteady Seepage in Reservoir During Hydraulic Fracturing with Unstable Injection

The current research on hydraulic fracturing with unstable injection mainly focuses on laboratory experiments or field tests. However, due to the difference in scale, some conclusions derived from laboratory experiments are not suitable for field applications. Besides, there is little research on coupling analysis of transient flow in tubing and seepage in reservoir during fracturing. In this paper, the transient dynamic model of fluid in tubing and the model of unsteady seepage in reservoir were established, respectively. Furthermore, the simulation model was established by parameters coupling, which took into account the influence of reservoir breakdown on permeability. The variation of fluid pressure in the tubing of different scale was analyzed during unstable injection. Simultaneously, the amplitude frequency characteristics of fluid in the tubing were also compared between laboratory scale and field scale. The results show that the simulation model can be used to calculate the fluid pressure variation in the whole process of hydraulic fracturing. And the simulation results are basically consistent with the experimental results. The scale difference has a significant impact on the variation of fluid pressure in tubing. To improve the fluctuation amplitude of outlet pressure, it is necessary to design the frequency according to the amplitude frequency characteristics of the corresponding scale model. It can also be achieved by reducing the resistance coefficient. The research can provide guidance for parameters design in field applications. It is conducive to understand the difference between laboratory experiments and field applications.