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Simulation of mass transfer in shale porous media continues to challenge the hydrocarbon recovery industry due the involved complex porous media transport mechanisms and complicated porous structures. In this paper, we present a new multiscale approach to improve the simulation of gas flow in shale porous media based on a coupled triple-continuum and discrete fracture model. Gas transport in shale formations entails porous media flow through matrix (which contains organic and inorganic matters) and fractures. The fractures consist of small-scale natural fractures and large-scale artificial fractures from hydraulic fracturing. In the triple-continuum model, kerogen matrix, inorganic matrix and natural fractures are modeled as three superimposed continua. The hydraulic fractures are handled by discrete fracture model. Using a framework via the multiscale mixed finite element method, our methodology couples the triple-continuum model and discrete fracture model in a rigorous and systematic approach. The method can capture the small-scale features of gas flow through multiscale basis functions calculated based on the triple-continuum background. We go beyond multiple-continuum modeling by enabling explicit discrete fracture representation in our multiscale framework. As a result, our approach could avoid some oversimplified assumptions made in conventional triple-continuum models and enjoy explicit fracture treatment with high computational efficiency. Numerical aspects of the new approach are detailed with examples demonstrating its efficiency and accuracy for simulating gas flow in shale porous media with multiscale porous features. [ABSTRACT FROM AUTHOR]

We present an E nhanced D iscrete F racture N etwork ( EDFN ) model for multiphase flow simulation in fractured reservoirs. EDFN can efficiently represent complex fractured porous media and accurately simulate fluid exchange between matrix and fracture. By using EDFN the fracture network is discretized with minimum number of grids based on the fracture intersecting points and fracture extremities. The matrix is also optimally decomposed into coarse blocks with different geometries using a rapid image processing algorithm. Each coarse matrix block is designed to be associated with one fracture grid and then discretized logarithmically to handle 1D flow between matrix and fracture. EDFN can greatly optimize the discretization for fractured porous media to conform interconnected fractures of arbitrary orientations. Via unstructured format, EDFN is successfully linked with an in-house unstructured compositional simulator. We validate the accuracy of EDFN through a number of multiphase flow simulations in fractured porous media with/without considering capillary pressure. Its efficiency is demonstrated to be superior by using a much less grid blocks comparing with other approaches. Ultimately EDFN is applied to predict hydrocarbon production in a shale oil reservoir and it enables to capture multi-scale fluid transfer in such complex system. [ABSTRACT FROM AUTHOR]

We present an adaptive Multiscale Mixed Finite Element Method (MsMFEM) for modeling multiphase flow in highly heterogeneous reservoir. In this framework, fractional flow model is used to approximate pressure and velocity solution on coarse scale, while resolution in fine scale is honored by the basis functions, which are calculated by local problems on fine scale. The adaptive computation in the flow problem is permitted by two different basis functions. In the numerical examples, our adaptive MsMFEM is applied to solve two dimensional and three dimensional reservoir simulation problems with highly heterogeneous porosity and permeability fields. The preliminary numerical simulation results presented show a significant speedup in comparison with the reference numerical method, which encourage and is beneficial for further investigation of the proposed method for reservoir numerical simulation. [ABSTRACT FROM AUTHOR]

Simulating flow in a highly heterogeneous reservoir with multiscale characteristics is computationally demanding. To tackle this problem, we propose a numerical scheme based on the Generalized Multiscale Finite Element Method (GMsFEM) and a triple-continuum model. The aim is to obtain a more efficient numerical approach that can explicitly represent the interactions among different continua. To enhance the applicability of our proposed model, we combine the Discrete Fracture Model (DFM) to model the local effects of discrete fractures. In the proposed model, the GMsFEM, as an advanced model reduction technique, enables capturing the multiscale flow dynamics. This is accomplished by systematically generating an approximation space through solving a series of local snapshot and spectral problems. The resulting eigenfunctions can pass the local features to the global level when acting as basis functions in the global coarse problems. Our goal in this paper is to further improve the accuracy of flow simulation in complicated reservoirs especially for the case when multiple discrete fractures located in single coarse neighborhood. Several numerical experiments are conducted to confirm the success of our proposed method, and a rigorous convergence proof is also given. [ABSTRACT FROM AUTHOR]