Numerical Simulation of Diverting Fracturing for Staged Fracturing Horizontal Well in Shale Gas Reservoir

Abstract

Hydraulic fractures are difficult to initiate simultaneously during multi-cluster fracturing owing to the strong heterogeneity of shale reservoir and the stress interference effect between adjacent hydraulic fractures. Some hydraulic fractures can initiate early and propagate rapidly, whereas others exhibit late initiation (or even fail to initiate) and propagate slowly, resulting in non-uniform propagation behavior of multiple fractures. This non-uniform propagation behavior can significantly limit hydraulic fracturing performance in shale gas reservoirs. Therefore, the minimization of non-uniform propagation of multi-cluster fractures is important in improving the shale gas development. Currently, diverting fracturing technology is implemented to restrain overextended fractures while promoting restricted fractures to facilitate uniform propagation. Pumping diversion balls to block the perforations of overlong fractures has become an important method to improve non-uniform fracture propagation. This method is, however, limited by lagging behind of theoretical simulation, and significant blindness in the current implementation of diverting fracturing. A dynamic propagation model for multiple-cluster hydraulic fractures was established in the current study by considering the stress interference effect between adjacent fractures and the effect of flowrate dynamic adjustment by diversion balls. This model is effective for the dynamic simulation of fractures propagation after pumping diversion balls. A fractured well in the Changning block was used as an example for the simulation of the dynamic fracture’s extension and the distribution of SRV before and after diversion. The findings showed that the temporary plugging ball significantly promoted the uniform extension. The number of temporary plugging balls, the number of diversions, and the timing of diversion were then optimized. The simulation method developed in this study has important theoretical significance and field application value in guiding regulation of uniform expansion of fractures and improving optimization of diverting fracturing design.