Transient production decline behavior analysis for a multi-fractured horizontal well with discrete fracture networks in shale gas reservoirs

Multi fractured horizontal well (MFHW) is extensively applied to develop the shale gas reservoirs. After massive fracturing, the complex fracture network will exist around the horizontal wellbore. To model the flow behavior more rigorously, the fractures within the network should be represented explicitly rather than idealized as dual-porosity media around the wellbore. Thus, a conceptual model of discrete fracture network for MFHW is first constructed by using the unstructured perpendicular bisection (PEBI) grid. Then, a mathematical model considering the stress sensitivity of the reservoir permeability, Darcy flow, diffusion, and adsorption and desorption in shale gas reservoirs is developed and the numerical nonlinear production decline equations are derived and obtained. Subsequently, the model is verified by a simplified model and production decline curves for a MFHW with discrete fracture networks in shale gas reservoirs are plotted. Five flow regions including early formation linear flow, interference flow among discrete fracture networks, compound pseudo-linear flow, pseudo radial flow, and pseudo-steady-state flow are identified. Finally, the sensitivity studies for the eight related parameters are conducted on the production decline type curves, and the production decline type curves of the MFHW are verified by a field case study. This study can provide very meaningful references for reservoir engineers to stimulate effectiveness and reservoir properties evaluation as well as production performance estimation of MFHW in shale gas reservoirs by matching the type curves with actual field data.