Optimizing Unconventional Reservoir Development: Efficient Multi-Well Performance Modeling Using the Boundary Element Method

Abstract In certain scenarios of unconventional resource development, reservoir geology enforces an irregular placement of wells and hydraulic fractures. The resulting reservoir-well architecture and the attendant subsurface flow pattern may thus pose formidable reservoir/well performance modeling challenges. Under this circumstance, analytical solutions compromise on the representation of actual reservoir- well geometries while numerical simulation suffers extreme gridding requirements and incurs extended runtimes. This study presents a practical semi-analytical solution for modeling multi-well performance in tight reservoirs, with rigorous representation of complex well geometries and exact consideration for well interference. The proposed solution utilizes the boundary-element method with an appropriate Green's function to model fully and partially penetrating hydraulic fractures of arbitrary azimuth. Well laterals are unrestricted in both orientation and deviation; the reservoir lateral boundaries can be arbitrary-shaped or of infinite extent. Multi-well production and interference are handled using the superposition principle. We benchmarked our solution against analytical and numerical models for variable well production (driven by either rate and pressure control), as well as for regular and irregular hydraulic fractures. The results are in excellent agreement. Verification cases highlight our solution's fit for modeling the flow behavior of fully and partially penetrating hydraulic fractures, notwithstanding the irregularity in fracture geometry. Three application examples are presented: the first evaluates completion effects on well performance and determines the optimum fracture spacing by evaluating incremental production; the second example examines interference from an infill well and its impact on the parent well's performance; the third example demonstrates application in history matching and long-term production forecast. The accuracy of this semi-analytical solution makes it useful for transient analysis and for initial calibration and verification of the more complex numerical simulation. Because of its rigorous multi-well modeling capability, it can also be deployed in synchronization with and as a reflection of actual field development for reservoirs producing single-phase oil or gas.