Effect of Mineral Dissolution/Precipitation and CO₂ Exsolution on CO₂ transport in Geological Carbon Storage

Abstract

Geological carbon sequestration (GCS) in deep saline aquifers is an effective means for storing carbon dioxide to address global climate change. As the time after injection increases, the safety of storage increases as the CO transforms from a separate phase to CO(aq) and HCO by dissolution and then to carbonates by mineral dissolution. However, subsequent depressurization could lead to dissolved CO(aq) escaping from the formation water and creating a new separate phase which may reduce the GCS system safety. The mineral dissolution and the CO exsolution and mineral precipitation during depressurization change the morphology, porosity, and permeability of the porous rock medium, which then affects the two-phase flow of the CO and formation water. A better understanding of these effects on the CO-water two-phase flow will improve predictions of the long-term CO storage reliability, especially the impact of depressurization on the long-term stability. In this Account, we summarize our recent work on the effect of CO exsolution and mineral dissolution/precipitation on CO transport in GCS reservoirs. We place emphasis on understanding the behavior and transformation of the carbon components in the reservoir, including CO(sc/g), CO(aq), HCO, and carbonate minerals (calcite and dolomite), highlight their transport and mobility by coupled geochemical and two-phase flow processes, and consider the implications of these transport mechanisms on estimates of the long-term safety of GCS. We describe experimental and numerical pore- and core-scale methods used in our lab in conjunction with industrial and international partners to investigate these effects. Experimental results show how mineral dissolution affects permeability, capillary pressure, and relative permeability, which are important phenomena affecting the input parameters for reservoir flow modeling. The porosity and the absolute permeability increase when CO dissolved water is continuously injected through the core. The MRI results indicate dissolution of the carbonates during the experiments since the porosity has been increased after the core-flooding experiments. The mineral dissolution changes the pore structure by enlarging the throat diameters and decreasing the pore specific surface areas, resulting in lower CO/water capillary pressures and changes in the relative permeability. When the reservoir pressure decreases, the CO exsolution occurs due to the reduction of solubility. The CO bubbles preferentially grow toward the larger pores instead of toward the throats or the finer pores during the depressurization. After exsolution, the exsolved CO phase shows low mobility due to the highly dispersed pore-scale morphology, and the well dispersed small bubbles tend to merge without interface contact driven by the Ostwald ripening mechanism. During depressurization, the dissolved carbonate could also precipitate as a result of increasing pH. There is increasing formation water flow resistance and low mobility of the CO in the presence of CO exsolution and carbona...

6. Multiphase Multicomponent Reactive Transport and Flow Modeling

“…Dissolution/precipitation reactions (not only induced by gas) modify hydrological properties such as the porosity, reactive surface area, and permeability at the pore-and core-scales (Gouze and Luquot 2011;Xu et al 2017). Moreover, CO 2 injection into a heterogeneous medium may create wormholes, depending on the relationship between geochemical reactivity and fluid motion (Snippe et al 2017).…”

“…These relationships are actually more complex than this relatively simple description, especially at small scales. For example, Xu et al (2017) demonstrated that mineral dissolution can enlarge pore throats, increase porosity and permeability, decrease capillary pressure, and influence relative permeability due to the injection of dissolved CO 2 in a Chaunoy sandstone core from the Paris Basin. A depressurization test revealed that gas exsolution and mineral precipitation may occur.…”

A screening framework study to evaluate CO2storage performance in single and stacked caprock–reservoir systems of the Northern Appalachian Basin

“…Henry's law was used to model CO 2 solubility into brine. The effect of CO 2 solubility into brine was included since it could be considered an intermediate trapping mechanism . Also, PVT properties of brine (such as brine density) are a function of CO 2 solubility .…”

“…The effect of CO 2 solubility into brine was included since it could be considered an intermediate trapping mechanism. 40,41 Also, PVT properties of brine (such as brine density) are a function of CO 2 solubility. 41 The amount of CO 2 trapped as residual gas in the aquifer was determined by the Land model.…”

CO2 Sequestration by Mineral Carbonation: A Review

“…However, significant developments are yet to arrive. Novel approaches for studying the basic mineral carbonation methods were suggested as there is a scope for advancement, including additive recovery, which has not been investigated thoroughly (Bobicki et al, 2015;Centi and Perathoner, 2014;Jafari et al, 2017;Li et al, 2013;Olajire, 2013;Paul et al, 2017;Xu et al, 2017). (Haug et al, 2010;Zhao et al, 2010) HNO3 extraction HNO3 used to extract reactive components…”