Role of gas multiple transport mechanisms and fracture network heterogeneity on the performance of hydraulic fractured multiwell-pad in unconventional reservoirs

Abstract

The hydraulic fractured multiwell-pad (HFMP) is gradually adopted as an efficient way to enhance shale gas recovery in shale reservoirs. Microseismic evidence supports that the fracture network heterogeneity can be expected in the overlap region initiated by multi-well fracturing. However, most modeling studies have focused on a single well, neglecting the enhanced stimulated reservoir volume (ESRV) between adjacent wells and the associated well interference. In this research, a novel semi-analytical solution for a shale gas reservoir model coupling fracture network heterogeneity and gas multiple transport mechanisms is derived. The proposed model can capture the gas desorption, diffusion, and viscous flow in matrix and gas viscous flow in fracture system as well as the properties of ESRV and SRV. The bottom-hole pressure (BHP) and production rate dynamics illustrate that the HFMP in a shale reservoir with ESRV and SRV apparently differs from the common single well model in the shale reservoir with homogeneous fracture network. Eight flow regimes can be recognized during shale gas development: wellbore storage flow, short-term transition flow, the first linear flow perpendicular to hydraulic fractures (HFs), the first radial flow around HFs, the second linear flow beyond the tip of HFs, the second radial flow in SRV region, transition flow, and the third radial flow regimes in USRV. Sensitive analyses demonstrate that ESRV permeability, well spacing, SRV size and permeability, and production rate difference between adjacent wells all exhibit significant effects on BHP and production rate performances. The findings obtained in this research shed light on the proper consideration of fracture network heterogeneity and gas viscous flow in shale matrix for reservoir evaluation and development.