Coupling Between Poromechanical Behavior and Fluid Flow in Tight Rock
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Coupling Between Poromechanical Behavior and Fluid Flow in Tight Rock Kiseok Kim1 · Roman Y. Makhnenko1 Received: 16 May 2020 / Accepted: 17 September 2020 / Published online: 6 October 2020 © Springer Nature B.V. 2020
Abstract Proper characterization of the mechanical and flow properties of participating rock formations is crucial for subsurface geo-energy projects, including hydrocarbon extraction, geologic carbon storage, and enhanced geothermal systems. Application of mechanical and hydraulic pressures changes the porosity of rock and modifies flow paths. For lowpermeable or “tight” rock that mainly contains nanoscale pores and serves as the confining layer for underground storage operations, a significant change in permeability may occur due to a small change in porosity. The pore volume changes in nanoporous geomaterials are extremely difficult to measure directly, but can be assessed from the knowledge of the hydro-mechanical response. Experimental methods to measure the stress-dependent permeability and poroelastic parameters of fluid-saturated tight rock are introduced. Eau Claire shale, Opalinus clay (claystone), and Charcoal granite are selected as representative materials for tight rock and their pore structure and material properties are carefully investigated. The porosity–permeability relationship for tight rock is established by adopting a power-law dependence with the exponent value in the range of 15–17, thus being significantly larger than that for a porous reservoir rock. Consequently, even small perturbations of porosity can cause orders of magnitude changes in permeability possessing a risk on the sealing capacity of the tight formations. Keywords Porosity · Permeability · Saturation · Shale · Opalinus clay
1 Introduction Establishment of porosity–permeability relationship for rock provides a straightforward way to couple its mechanical and hydraulic behavior thus being a topic of investigation in geophysical and petroleum engineering research. Fluid flow through the subsurface rock is affected by the external stress and internal pore pressure that affect the pore structure and modify the flow paths (Bear 1972; Biot 1973). Porosity and permeability are well-known as essential properties that can be selected to represent the pore space and hydro-mechanical * Kiseok Kim [email protected] 1
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Ave, Urbana, IL 61801, USA
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behavior of subsurface rocks (Quintard 1993). For petroleum engineering and sustainable geo-energy applications, such as enhanced geothermal systems (EGS), geological carbon storage (GCS), and radioactive waste disposal, understanding these characteristics is of great interest because corresponding reservoir formations require adequate storage capacity and flow efficiency, while the stability in terms of leakage should be carefully evaluated for the tight sealing layers (Tsang et al. 2005; Ezekwe 2010; Rutqvis
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