Multi-Stage Fractured Horizontal Well Numerical Simulation and Its Application in Tight Shale Reservoirs

Abstract

Abstract Unconventional tight shale reservoirs have been developed during recent years due to increasing shortage of conventional resources and a large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in tight shale reservoirs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the shale gas reservoir with MsFHW is influenced by both reservoir condition and hydraulic fracture properties. In this paper, a dual-porosity-dual-permeability model was presented to estimate the effect of parameters on shale gas production. Three flow mechanisms have been considered in this model: gas diffusion in nano scale pores, Darcy flow in macro scale pores, and non-Darcy flow in near wellbore hydraulic fractures. Langmuir isotherm was used to simulate the gas desorption process. Hydraulic fractures were performed by Local Grid Refinement (LGR) method. To conduct sensitivity anlaysis on production performance of tight shale reservoirs with MsFHW, parameters influencing shale gas production were classified into two categories: reservoir properties (including matrix permeability, matrix porosity, natural fracture porosity, rock compressibility, gas desorption) and hydraulic fracture properties (including hydraulic fracture spacing, fracture half-length, fracture conductivity, and fracture height). Typical ranges of these parameters have been reviewed. Sensitivity checks for each parameter were performed to analyze the effect of factors on the cumulative gas production. It can be found that matrix porosity is the most influencing reservoir parameter which has greatest effect on cumulative production among reservoir parameters. And hydraulic fracture spacing, fracture half-length, fracture conductivity, and fracture height are all significant parameters. Result of this study can be used to improve the efficiency of history matching process. Also, it can contribute to the design and optimization of hydraulic fracture treatment design in unconventional tight reservoirs.