A New Numerical Simulation Method for Multi-stage in-Fracture Temporary Plugging and Diverting Fracturing: Based on the Modified Cohesive Zone Model

The multi-stages in-fracture temporary plugging and diverting fracturing technology (ITPDF) is significant for the stimulation of unconventional oil and gas reservoirs. However, the propagation pattern of hydraulic fracture and the pressure response law after temporary plugging still lacks some understanding affected by many factors. Hence, to deeply understand the fracture diverting propagation mechanism and pressure response law after in-fracture temporary plugging, the study developed first a numerical model of cohesive zone considering in-fracture temporary plugging, seepage and fracture propagation based on the effective viscosity characterization method and the USDFLD (user defined field) subroutine. In addition, the accuracy of the numerical model is verified by comparing with laboratory results. The effect of different parameters such as temporary plugging body permeability, temporary plugging body length, temporary plugging location, temporary plugging times, and stress difference on the temporary plugging and diverting behavior of hydraulic fractures and natural fractures are deeply investigated. The fracture diverting pattern, fracture initiation sequence, and pressure response mechanism are clarified for different in-fracture plugging conditions. The results show that the physical properties of the temporary plugging body are vital to the effectiveness of the in-fracture temporary plugging fracturing. The lower the permeability of the temporary plugging body, the longer the length of the temporary plugging body, and the closer the position of the temporary plugging body, the easier it is to activate the natural fractures. In addition, when there are many natural fractures, the more times of temporary plugging, the more range and number of natural fractures are activated. This study can provide a new method to further understand the fracture behavior after in-fracture temporary plugging fracturing. A new numerical simulation method for multi-stage in-fracture temporary plugging and diverting fracturing was developed based on modified cohesive zone modelThe effect of temporary plugging body properties and the formation properties are deeply investigated.The horizontal stress difference determines the plugging function of the plugging body and the turning pattern of the fracture.