Pore-space alteration induced by brine acidification in subsurface geologic formations

Abstract

[1] A new Lagrangian particle-based method is presented to simulate reactive transport in natural porous media. This technique is based on Modified Moving Particle Semi-implicit (MMPS) and takes as input high-resolution voxel images of natural porous media. The flow field in the medium is computed by solving the incompressible Navier-Stokes equations. Moreover, a multicomponent ion transport model is coupled with a homogeneous and heterogeneous reactions module to handle pore-space alteration (i.e., pore-wall dissolution). The model is first successfully validated against the experimental data available in the literature. Subsequently, X-ray microtomographic images of two naturally occurring porous media are used to investigate the impact of reaction kinetics and pore-space topology on pore-space alteration induced by brine acidification in subsurface conditions. We observed that at the normal rates of reactions no significant change in porosity and permeability takes place in the short term. Whereas, higher reaction rates caused major changes in the macroscopic properties (e.g., porosity and permeability) of the rocks. We also show that these changes are strongly affected by the rocks' pore-scale topologies.Citation: Ovaysi, S., and M. Piri (2014), Pore-space alteration induced by brine acidification in subsurface geologic formations, Water Resour. Res., 50,[440][441][442][443][444][445][446][447][448][449][450][451][452]

Modelling of multispecies reactive transport on pore-space images

“…For example, Lichtner and Kang (2007b) proposed a method to upscale reactive transport equations from lattice Boltzman simulations, while Kim et al (2011) and Nogues et al (2013) used pore network models to calculate upscaled properties. Pore-scale experiments and models have been shown to be able to provide insights into the behaviour of reactive flow in porous media (Szymczak and Ladd, 2009;Ovaysi and Piri, 2014;Pereira Nunes et al, 2016), the source of the scale dependency of mineral reaction rates (Kang et al, 2010;Molins et al, 2012), and have been used to compute upscaled properties -such as overall reaction rate -for use in larger-scale models (Porta et al, 2012;Noiriel et al, 2012;Varloteaux et al, 2013).…”

Changes in porosity, permeability and surface area during rock dissolution: Effects of mineralogical heterogeneity

“…The heterogeneity of porous media in geological formations is embodied by the heterogeneous porous structures [14][15][16][17][18][19][20][21][22] as well as the mineralogical heterogeneity because of multiple components [23][24][25][26][27]. In such heterogeneous porous media, the observed reactive transport processes do not always behave according to the transport laws established for the homogeneous ones [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. For continuum-scale reactive transport modeling applied at large scales, the physicochemical heterogeneities are necessarily ignored at scales smaller than the size of the model discretization [4].…”

“…Theoretically, full resolutions of the spatial medium heterogeneity as well as the detailed mineral distributions down to the pore scale, with all the physicochemical processes considered, can help to understand the distinct reactive transport phenomena, to establish the reactive transport laws, and to reveal coupled mechanisms in heterogeneous porous media. The transport of a reactive fluid through a porous medium with dissolution is a very complex process encompassing multiple physicochemical sub-processes including fluid flow, species transport, chemical reactions, and alternations of solid and porous structures [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. These sub-processes occur simultaneously and are closely coupled with each other.…”

“…One is to understand the underlying reactive transport phenomena and to reveal the coupled mechanisms between different processes. Pore-scale simulations have revealed a complex coupling between convection, diffusion and dissolution reaction under the effects of structural heterogeneity [3,14,[18][19][20]22]. Different dissolution patterns have been found including uniform dissolution, face dissolution and wormhole dissolution under different reactive transport conditions.…”

Reactive Transport in Evolving Porous Media

“…This was likely due to variations in heterogeneity caused by dissolution reactions in advective regimes. In other words, a constant fitting parameter n might not be suitable to describe the evolution for substantial modifications of porosity (Pape et al 1998;Bernabé et al 2003;Nogues et al 2013;Ovaysi and Piri 2014;Vialle et al 2014).…”