A lattice-Boltzmann study of permeability-porosity relationships and mineral precipitation patterns in fractured porous
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ORIGINAL PAPER
A lattice-Boltzmann study of permeability-porosity relationships and mineral precipitation patterns in fractured porous media Mehrdad Ahkami1 · Andrea Parmigiani2 · Paolo Roberto Di Palma3 · Martin O. Saar1,4 · Xiang-Zhao Kong1 Received: 15 July 2019 / Accepted: 11 December 2019 © Springer Nature Switzerland AG 2020
Abstract Mineral precipitation can drastically alter a reservoir’s ability to transmit mass and energy during various engineering/natural subsurface processes, such as geothermal energy extraction and geological carbon dioxide sequestration. However, it is still challenging to explain the relationships among permeability, porosity, and precipitation patterns in reservoirs, particularly in fracture-dominated reservoirs. Here, we investigate the pore-scale behavior of single-species mineral precipitation reactions in a fractured porous medium, using a phase field lattice-Boltzmann method. Parallel to the main flow direction, the medium is divided into two halves, one with a low-permeability matrix and one with a high-permeability matrix. Each matrix contains one flow-through and one dead-end fracture. A wide range of species diffusivity and reaction rates is explored to cover regimes from advection- to diffusion-dominated, and from transport- to reaction-limited. By employing the ratio of the Damk¨ohler (Da) and the Peclet (Pe) number, four distinct precipitation patterns can be identified, namely (1) no precipitation (Da/Pe < 1), (2) near-inlet clogging (Da/Pe > 100), (3) fracture isolation (1 < Da/Pe < 100 and Pe > 1), and (4) diffusive precipitation (1 < Da/Pe < 100 and Pe < 0.1). Using moment analyses, we discuss in detail the development of the species (i.e., reactant) concentration and mineral precipitation fields for various species transport regimes. Finally, we establish a general relationship among mineral precipitation pattern, porosity, and permeability. Our study provides insights into the feedback loop of fluid flow, species transport, mineral precipitation, pore space geometry changes, and permeability in fractured porous media. Keywords Lattice-Boltzmann method · Fractured porous media · Mineral precipitation patterns · Permeability-porosity relationships
1 Introduction Chemical, thermal, and/or pressure equilibria in reservoirs are likely perturbed due to various engineering/natural subsurface processes, such as geothermal energy extraction, geological carbon dioxide (CO2 ) sequestration, and Xiang-Zhao Kong
[email protected] 1
Geothermal Energy and Geofluids Group, Institute of Geophysics, ETH Zurich, CH-8092, Zurich, Switzerland
2
FlowKit-Numeca, Route d’Oron 2, 1010 Lausanne, Switzerland
3
National Research Council of Italy, Water Research Institute, Area della Ricerca di Roma 1-Montelibretti, Strada Provinciale 35d, km 0.7 Montelibretti (Roma), Italy
4
Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA
biomineralization. Disturbance of such equilibria can trigger chemical reactions, such as dissolution and precipitati
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