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In recent years, shale gas has become an important energy source due to its abundant reserves. Due to their extremely tight initial properties, shale gas reservoirs require the use of the multi-stage fractured horizontal well (MFHW) technique to break the shale rock, activate closed natural fractures, and form a complex fracture network. In this study, to solve the issue of how to describe the fracture network's geometry and to predict the production performance accurately, a model that couples the fracture propagation with the fracturing fluid and proppant flow in a horizontal wellbore and hydraulic fractures is established. The displacement discontinuity method (DDM) and finite volume method are used to iteratively obtain numerical simulations of the fracture propagation. The accuracy of the fracture propagation model is verified through comparison with analytical and numerical models. Then, the coupled continuous media and discrete fracture network model considering multiscale flow mechanisms in shale is developed, which is solved numerically using the control volume finite element method (CVFEM) and unstructured tri-prism grids. Finally, the numerical simulation models are successfully applied to synthetic and field cases, sensitivity analysis is conducted to evaluate the influences of the proppant injection, stress anisotropy and distribution of the natural fractures on the fracture propagation and production performance of the MFHW in a shale gas reservoir. • The model couples the fracture propagation with fracturing fluid and proppant flow is established and solved. • The coupled continues media and discrete fracture network model is promoted, and solved by CVFEM and unstructured grids. • Sensitivity analysis is conducted to evaluate the influences on the fracture propagation and production performance. [ABSTRACT FROM AUTHOR]

A numerical method is employed to investigate the fluid flowing dynamics in fractured reservoirs in this paper. Owing to the multi-scales and strong heterogeneity, description of fracture network systems plays a significant role for a successful fractured reservoir simulation model. Comparing to previous works, this paper proposes a combination of dual continuum and discrete fracture network (DFN) model, which is used to simulate the flow in reservoirs with multi-scale fractures and proved feasible. In the first part of the paper, implicit flow equations of oil and water phase in fractured reservoirs are established to consider the nonlinearity properties. And then the control volume finite element method based on the unstructured grid system and N-R iteration are used to obtain the numerical solution. Moreover, the accuracy of this simulator is proved to be reasonable by field data; Sensitivity analysis shows that the existences of complex multi-scale fracture networks have great impacts on water flooding. Compared with the homogeneous reservoir, natural fracture (micro and large scale) networks can change the direction and velocity of the waterfront, which finally leads to the more serious water breakthrough, higher water cut and less recovery. The research and the numerical results obtained in this paper can provide theoretical guidance for efficient and scale development of natural fractured reservoirs. [ABSTRACT FROM AUTHOR]

In recent years, the greenhouse gas control has been a hot issue. A solution of injecting supercritical CO 2 (scCO 2) in Longmaxi shale gas formation (in Southwest China) is proposed in this study. To evaluate the feasibility of this method that storing CO 2 and enhanced gas recovery (EGR) simultaneously, we first carried out isothermal adsorption experiments on samples from Longmaxi formation to describe the adsorption behavior of CH 4 and CO 2 , and a generalized Ono-Kondo Lattice (OK) model was applied to predict adsorption amount of pure CH 4 /CO 2 and their binary mixtures under supercritical, high-pressure conditions. In addition, discrete fracture network (DFN) model was adopted to characterize the complex hydraulic fracture networks constructed from micro-seismic monitoring (MSM) data and engineering analysis. The porous flow in shale matrix was modeled with the multiple interacting continua (MINC) and fractal theories. A multiscale compositional numerical model based on unstructured tri-prism grids was finally developed and solved by control volume finite element (CVFE) method. The simulation results of base and CO 2 injection cases presented that scCO 2 huff 'n' puff in Longmaxi formation might be an effective method for CO 2 storage and EGR, and the orthogonal experiments were designed to optimize scenarios in the field application and obtain a maximum balanced result of EUR and CO 2 storage capacity (CSC) for multistage fractured horizontal well (MFHW) with complex fracture networks in shale. • The OK model was applied to predict pure CH 4 /CO 2 and their mixtures adsorption amount under supercritical conditions. • The hybrid DFN and MINC model was established to describe the flow in fractal porous media and complex fracture system. • The CVFE simulator was successfully conducted for comprehensive analysis of mechanisms of scCO 2 storage and EGR in shale. [ABSTRACT FROM AUTHOR]