Combination of MRI and SEM to Assess Changes in the Chemical Properties and Permeability of Porous Media due to Barite Precipitation

Abstract

The understanding of the dissolution and precipitation of minerals and its impact on the transport of fluids in porous media is essential for various subsurface applications, including shale gas production using hydraulic fracturing (“fracking”), CO2 sequestration, or geothermal energy extraction. In this work, we conducted a flow through column experiment to investigate the effect of barite precipitation following the dissolution of celestine and consequential permeability changes. These processes were assessed by a combination of 3D non-invasive magnetic resonance imaging, scanning electron microscopy, and conventional permeability measurements. The formation of barite overgrowths on the surface of celestine manifested in a reduced transverse relaxation time due to its higher magnetic susceptibility compared to the original celestine. Two empirical nuclear magnetic resonance (NMR) porosity–permeability relations could successfully predict the observed changes in permeability by the change in the transverse relaxation times and porosity. Based on the observation that the advancement of the reaction front follows the square root of time, and micro-continuum reactive transport modelling of the solid/fluid interface, it can be inferred that the mineral overgrowth is porous and allows the diffusion of solutes, thus affecting the mineral reactivity in the system. Our current investigation indicates that the porosity of the newly formed precipitate and consequently its diffusion properties depend on the supersaturation in solution that prevails during precipitation.

Studies of Mineral Nucleation and Growth Across Multiple Scales: Review of the Current State of Research Using the Example of Barite (BaSO4)

“…Pore-scale reactive transport modeling has been applied to growth and dissolution of various mineral systems and the model outputs can be directly compared with microfluidics and/or small-scale batch reactor experiments. ,,− While pore-scale reactive transport models have mostly been used to predict dissolution and precipitation of carbonates (e.g., CaCO 3 ), barite and its corresponding solid solutions have also been utilized for experimentally benchmarking these models. − Many parameters can affect the accuracy of the pore-scale models, therefore a careful review of the possible physical and chemical processes in modeled system is required. For example, including comprehensive information on the microstructure (i.e., topology of pores) and modified porosity-permeability parameters into a 2D reactive transport model was needed to successfully reproduce micro-to-pore scale observations of barite precipitation following celestite dissolution .…”

Microfluidic flow-through reactor and 3D Raman imaging for in situ assessment of mineral reactivity in porous and fractured porous media

“…In the last decades, there has been a growing interest to use pore-scale modelling in combination with experimental imaging/characterisation of porous media as tools to get a better understanding of coupled chemical and transport processes and to upscale the results to a macroscopic representation 2,[14][15][16][17] . A live monitoring of chemical processes and hydraulic pathways can be performed using non invasive techniques such as magnetic res-onance imaging 18 , positron emission tomography 19 , or neutron imaging 20 . The spatial resolution, however, is often a limiting factor for these techniques.…”

Barite Scaling Potential Modelled for Fractured-Porous Geothermal Reservoirs

“…The Kozeny-Carman relationship was used for porous media and the cubic law was used for the fractures. While these idealised model approaches are commonly used in this regard [20], significant deviations are possible under certain conditions (e.g., [17,19,38,62]). For fractures, many characteristics can be attributed to a departure from the cubic law, including aperture fluctuations, surface roughness, and pore fluid exchanges with the surrounding matrix [63].…”