Numerical modeling of hydraulic fracture propagation behaviors influenced by pre-existing injection and production wells

Hydraulic fracturing treatments are capable of enhancing the well production performance in low-porosity and low-permeability reservoirs because of the resulted improvement in communication between the formation and wellbore through created hydraulic fractures (HFs). In fact, not only the in-situ stress underground but also the pre-existing offset wells induced non-uniform pore pressure field will influence the HF propagation process. In this work, to investigate the HF propagation behaviors under the effects of adjacent production and injection wells, a new numerical model is developed within the framework of extended finite element method (XFEM) and cohesive zone method (CZM). The model can simultaneously simulate the HF initiation, propagation and re-orientation, fracturing fluid flow and leakoff, formation fluid flow and rock deformation. Reliability of the new model is validated by comparing the numerically calculated fracture geometry with the experimental observation in the literature. The interesting and new results show that pore pressure field, stress field and fracture propagation speed can be altered around the pre-existing offset wells. Also, HF prefers to propagate toward injection wells when production and injection wells co-exist, and the fracture propagation trajectory will not be affected in the cases that only production or injection wells exist. The fracture will be shorter and wider when only injection wells exist or production and injection wells co-exist, while the pre-existence of only production wells leads to a longer and thinner HF. Moreover, a smaller pumping pressure can be applied to generate the HF when only production wells locate nearby, while a greater injection pressure is required to drive the HF forward when only injection wells pre-exist or injection and production wells co-exist. The obtained results provide new insights for understanding the fracture propagation behaviors in the field scale.