A wellbore-fracture coupled fracturing model to simulate non-uniform fracture propagation under multiple clusters of fracturing

Abstract

Multiple clusters of fracturing within one stage have been widely used in the unconventional reservoir production. However, the non-uniform fracture propagation under multiple clusters of fracturing has not yet fully been understood, due to the fluid flow in the wellbore being neglected in the fracturing model. In view of this, a wellbore-fracture coupled fracturing model was established to simulate fracture non-uniform propagation under multiple clusters of fracturing. In this model, the governing equation was firstly given based on the pressure continuity and flow conservation, to obtain the flow distribution in each fracture. Then, equations of fracture propagation, fracture height growth and stress shadow were combined to determine the fracture geometric parameters. Substituting fracture geometric parameters into the governing equation, the wellbore-fracture coupled fracturing model was finally solved. The proposed model was validated by a ABAQUS cohesive elements numerical by comparing the fracture parameters, respectively considering conditions of wellbore-fracture coupling and non-wellbore-fracture coupling, within a maximum deviation that did not exceed 6.14%. Using the proposed model, the parametric analyses were performed, including energy-related parameters and wellbore-related parameters. For energy-related parameters, with the increase of surface energy density of rock and the minimum principal stress, the fracture length and height decreased, while the fracture width increased to some extent. In addition, with the increase of pumping rate of fracturing fluid, the fracture length, height and width increased significantly. For wellbore-related parameters, with the decrease of diameter of perforation and perforation number as well as the increase of wellbore roughness coefficient and viscosity of fracturing fluid and cluster distance, the flow distribution in each fracture and the injection pressure became more uniform and the non-uniform propagation of each fracture was reduced, but fracture dimensions were simultaneously decreased.