COMPREHENSIVE PRODUCTION ANALYSIS FOR SHALE GAS WELLS CONSIDERING MULTI-NONLINEAR FLOW MECHANISMS AND HETEROGENEOUS SRV

Abstract

Unlike conventional reservoirs, prediction of production for shale gas wells is hardly reached by analytical models for accurately characterizing nonlinearity caused by multiple transport mechanisms of shale gas and the heterogeneity of stimulated reservoir volume (SRV). Given the limitations of analytical solutions, we adopted the finite difference method (FDM) in this paper to approximate the classic three-region model and obtained an effective numerical solution in which the pressure-dependent dynamic properties, such as gas desorption; pressure, volume, and temperature (PVT) properties; various transport mechanisms; and stress-dependent fracture permeability are considered in the modeling. The results explain that (1) the production predicted with the numerical method is accurate for the nonlinearity in the model being dealt with properly; (2) the field case shows the veracity of the proposed approach, and gas production and estimated ultimate recovery (EUR) can be evaluated with this model; (3) gas viscosity and Z-factor have an important impact on the initial production, which should be emphasized in rate transient analysis (RTA) for early-time production; slippage flow and diffusion of shale gas increase the productivity of gas wells; desorption in shale matrix can enhance middle- and long-term production; and the stress-sensitive effect and heterogeneity of SRV obstruct gas flow and reduce the total gas production; and (4) an optimized production strategy for controlling pressure drawdown is of great importance. Consequently, the refracturing treatment might be an effective measure to alleviating formation pressure drawdown, improving gas desorption and SRV permeability.