Mechanism Analysis of Well Interference in Unconventional Reservoirs: Insights From Fracture-Geometry Simulation Between Two Horizontal Wells

Abstract

Summary Well interference is a common phenomenon between wells observed in unconventional reservoirs, which has received significant attention. It plays an important role in well-spacing considerations. Massive hydraulic fractures are generated in horizontal wells by multistage hydraulic-fracturing treatments and result in well interference between adjacent wells. However, very little work has been completed to understand how massive fractures cause well interference. In this study, we analyzed dynamic-stress evolution and multiple-fracture propagation from two horizontal wells to improve understanding of fracture hits. We used our newly developed nonplanar hydraulic-fracturing model that couples rock deformation and fluid flow in the fracture and horizontal wellbore. Fracture propagation in a stage is controlled by stress-shadow effects and flow-rate distribution between fractures. Fracture interaction within a stage and from adjacent wells is considered through a simplified 3D displacement discontinuity method. Well interference is well communication caused by fracture hits. Because of varying stress reorientation, fractures propagate toward each other from two adjacent wells, and fracture tips always tend to converge with each other and decrease fracture distance, which promotes fracture coalescence. For plug-and-perforate completion, multiple fractures in a stage generally cannot uniformly develop. Dominant fractures with extremely long length are often generated and hit fractures from adjacent wells. Fracture hits and well interference are induced by these two mechanisms, which are affected by fracture spacing and the differential stress (DS) of reservoirs. Results show that the larger the fracturing spacing is, the smaller the likelihood is to induce fracture connection. A large DS can prevent fractures from deviating from their original paths. For a reservoir with a large DS, fracture hits can be decreased with a stagger distance of fractures between two wells. This work uses a hydraulic-fracturing model to analyze fracture geometry between two horizontal wells and offers improved understanding of fracture connection. The results of the study provide critical insights to improve well interference and to optimize well spacing and design of multiwell completion techniques.