Pseudo-three-dimensional numerical model and investigation of multi-cluster fracturing within a stage in a horizontal well

Abstract

Multi-cluster fracturing and horizontal drilling are the key techniques used to exploit unconventional reservoirs. However, field production has revealed that certain perforation clusters are invalid. In order to find the most effective approaches to improve the uniformity of multiple-fracture growth, a pseudo-3D multi-cluster fracturing model is established in this study. In our model, complex in-situ stress distributions are considered and the stress interactions between fractures are calculated using the displacement discontinuity method (DDM). Fluid dynamic flow distributions into different clusters are calculated using Kirchhoff's second law. Fracture height and length extension velocities are determined based on the fracture edge energy release rate. The effectiveness of our model is verified by comparing the single fracture extension results obtained by our model to those obtained by a semi-analytical model. Based on our numerical model, possible approaches to promoting the uniform growth of multiple fractures are discussed. The results indicate that adjusting spacing is an inefficient method to promote multiple-fracture uniform growth under the condition of four clusters fracturing within a stage. However, regulating perforation friction, reducing fracturing fluid viscosity, and increasing injection rate are useful ways to improve the uniformity of multiple-fracture propagation.