期刊
ADVANCES IN WATER RESOURCES
卷 122, 期 -, 页码 70-84出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.advwatres.2018.10.004
关键词
Shale gas; Nanoporous media; Micro-continuum; Darcy-Brinkman-Stokes
资金
- NERC-UK [NE/M001458/1]
- Research Complex at Harwell
- European Union Horizon 2020 716 Research and Innovation Program under the ShaleXenvironmenT project [640979]
- TOTAL through the Stanford TOTAL enhanced modeling of source rock (STEMS) project
- NERC [NE/M001458/1] Funding Source: UKRI
The physical mechanisms that control the flow dynamics in organic-rich shale are not well understood. The challenges include nanometer-scale pores and multiscale heterogeneity in the spatial distribution of the constituents. Recently, digital rock physics (DRP), which uses high-resolution images of rock samples as input for flow simulations, has been used for shale. One important issue with images of shale rock is sub-resolution porosity (nanometer pores below the instrument resolution), which poses serious challenges for instruments and computational models. Here, we present a micro-continuum model based on the Darcy-Brinkman-Stokes framework. The method couples resolved pores and unresolved nano-porous regions using physics-based parameters that can be measured independently. The Stokes equation is used for resolved pores. The unresolved nano-porous regions are treated as a continuum, and a permeability model that accounts for slip-flow and Knudsen diffusion is employed. Adsorption/desorption and surface diffusion in organic matter are also accounted for. We apply our model to simulate gas flow in a high-resolution 3D segmented image of shale. The results indicate that the overall permeability of the sample (at fixed pressure) depends on the time scale. Early-time permeability is controlled by Stokes flow, while the late-time permeability is controlled by non-Darcy effects and surface-diffusion.
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