Multiscale model reduction for shale gas transport in a coupled discrete fracture and dual-continuum porous media

Natural gas production from shale formations involves highly complex geological features consisting of fractures that are embedded spatially-distributed in a matrix made of organic and inorganic materials. In this paper, we develop a coupled multiscale and multi-continuum approach for simulating gas transport in the shale formation. The multiscale method allowed us to capture detailed interactions between the fractures and the background. For the fine-scale heterogeneities involving organic and inorganic materials distribution in the matrix, we use a dual-continuum approach. The matrix is coupled to the fractures by use of the Generalized Multiscale Finite Element Method (GMsFEM). In our previous work (Akkutlu et al., 2016), we used a single-continuum background coupled to the fracture network. This paper presents a significant extension and considers dual-continuum media as a background. GMsFEM systematically identifies the fracture networks by constructing corresponding multiscale basis functions. GMsFEM also accurately represents the fractures interacting with the background media. Moreover, GMsFEM can handle any spatial fracture distributions and thus, it avoids the limitations of the multi-continuum approaches. Results show that the proposed numerical approach can accurately capture the interactions between the fractures and the multi-continuum model using a few multiscale basis functions.