Transient pressure and production dynamics of multi-stage fractured horizontal wells in shale gas reservoirs with stimulated reservoir volume

Abstract

Multi-stage fracturing in unconventional shale gas reservoirs always creates complex fracture network around horizontal wellbore. The existence of the stimulated reservoir volume (SRV) has significant impact on performance of fractured horizontal well, and various composite models are introduced to simulate gas flow caused by fractured horizontal wells with SRV. However, most of the existing models do not simultaneously taken into account fracture conductivity, non-uniform properties of hydraulic fractures, SRV region, multiple flowing mechanisms of shale gas.This paper extends previous work by presenting a more comprehensive model to simulate the performance of multi-stage fractured horizontal well in shale gas reservoirs. The model takes into account not only the existence of SRV, but also the influence of fracture conductivity, multiple flowing mechanisms (desorption, transient state and pseudo-steady state viscous flow and diffusion) in shale matrix as well as the effect of non-uniform fracture distribution. By employing the source function theory, Laplace transformation and discretization method, a relatively simple semi-analytical solution is obtained. After the verification of the presented model with other published results, the transient pressure and production dynamics are compared and analyzed. The influences of relevant parameters on performance of fractured horizontal wells are also discussed. It is found that the performance of fractured horizontal wells in shale gas reservoirs is mainly affected by the parameters related to SRV (the size of SRV, the density of fractures in SRV, the configuration of primary fractures in SRV), conductivity and distribution of hydraulic fractures, and desorption and diffusion in shale matrix. The model presented in this paper can be easily simplified to simulate simpler cases, such as performance of fractured horizontal wells in tight reservoirs. The model and corresponding conclusions presented in this study will be helpful to understand transient performance of multi-stage fractured horizontal wells in shale gas reservoirs and thus to effectively develop unconventional shale gas reservoirs.