Unconventional Reservoir Flow Simulation: an Improved Boundary Element Fracture Modeling Technique and the Influence of Multi-Component Diffusion/Adsorption
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The natural fractures and hydraulic fractures often form complex fracture network in shale reservoirs, which poses great challenge to the flow simulation of such complex reservoirs. In this study, a theoretically sound, and practically robust boundary element method (BEM) numerical algorithm is developed and successfully implemented. Explicit and discrete fracture description is adopted in this approach, and the complex fracture settings and interactions are effectively simulated. Comparing with the domain discretization methods (e.g., finite element method (FEM), finite difference method (FDM)), mesh generation is greatly simplified in our approach, especially for reservoirs with complex fracture configurations. Case studies show: our algorithm is capable of modeling two-dimensional (2D) steady state flow in fractured reservoirs with different boundary conditions and complex fracture networks; also, the transient flow dynamics and the flow dependence on matrix heterogeneity, which are seldom considered through a BEM approach, are successfully accounted for; in addition, by characterizing the fracture flow using finite volume element (FVM) formulation, the fluid flow in three-dimensional (3D) fractured reservoirs with irregular fractures is properly handled through this algorithm. Multiple porosity systems (especially organic matter) existing in shale reservoirs require a reservoir simulator to properly account for the multi-component diffusion/adsorption phenomena occurring in the matrix. A compositional model specifically tailored for the characteristics of shale reservoirs is thus developed. The model takes the pressure and component molar masses as the primary variables, and the IMPEM (implicit pressure and explicit mass) method as the solution technique. The multi-component adsorption and diffusion influences are shown to be successfully accounted for through this model. Case studies indicate: the multi-component adsorption which mainly exists in the shale organic matter usually plays a positive role in shale reservoir recovery; the influence of the different TOC values on shale fluid recovery may be different depending on the fluid type and the operating conditions; and the multi-component diffusion facilitates the gas recovery, yet the degree of this improvement differs for different wettability formations.
boundary element method (BEM)
Cao, Yang (2018). Unconventional Reservoir Flow Simulation: an Improved Boundary Element Fracture Modeling Technique and the Influence of Multi-Component Diffusion/Adsorption. Doctoral dissertation, Texas A & M University. Available electronically from