Ranking of Geologic and Dynamic Model Uncertainties for Carbon Dioxide Storage in Saline Aquifers

Abstract

Growing concerns over global climate change is also increasing the interest in developing technologies to reduce the concentration of carbon dioxide (CO2) in the atmosphere. Geological Carbon Sequestration which injects CO2 into subsurface formations such as deep saline aquifers, depleted hydrocarbon reservoirs are some of the viable options to reduce CO2 emissions into the atmosphere. Deep saline aquifers are a particularly good choice due to their wide geographical distribution and proximity to emission sources that provide easy accessibility and storability of CO2. Saline aquifers, however, are data-poor systems that requires a thorough understanding of the impact of all factors and their uncertainties on long-term CO2 storage for risk assessment. This study considers a wide range of geologic and dynamic model uncertainties, including structural uncertainties, petrophysical heterogeneities, dynamic flow parameters and geochemical reactions to define the most critical parameters for different CO2 trapping mechanisms. Experimental design over stochastic modelling and sampling is used to minimize the computational cost of the study. A commercially available, compositional reservoir simulator with reactive transport modeling capability has been used in this study to account for the impact of potential geochemical reactions. Assumed reactive transport model considers the water solubility, ionization, and mineral trapping mechanisms of CO2 in saline reservoirs for a range of components of dissolved salts in the brine as well as the pH of the brine. Chemical reactions that may occur with the rock minerals (Kaolinite, Anorthite and Calcite) when adding the CO2 are prescribed as input into the simulator. Simulations also include effects of hysteresis and diffusion processes. Study shows that the most important parameter for all trapping mechanisms is the permeability since it controls the injection capacity. Beyond that, different combination of parameters with different range of uncertainties alter the ranking of factors influencing dissolution, ionization, hysteresis, mineralization and the movement of CO2 within the aquifer. There is no unique set of parameters that maximizes all storage mechanisms. There is a significant overlap and change in amount the amount of CO2 stored via different mechanisms depending on the parameter combinations. Study results also provide insights into how one can prioritize data gathering needs depending on the objectives, data uncertainties and their sensitivities for an aquifer site under consideration.

Unveiling the Essential Parameters Driving Mineral Reactions during CO2 Storage in Carbonate Aquifers through Proxy Models

“…Figure 8 presents the updated Tornado plots for the objective functions (OFs) "Cal-cite_1000yr" and "Dolomite_1000yr". The findings support the observations made by Ates et al [11], as the CO 2 injection rate emerges as the most influential parameter. This parameter plays a crucial role in fueling the calcite dissolution reaction, which, in turn, is closely linked to the growth of dolomite, as evidenced by the right Tornado plot in Figure 8.…”

“…Building upon the foundational research on uncertainty assessment conducted by Ates et al [11], who suggested that geochemical reactions become more significant at higher CO 2 injection rates, a new experimental design incorporated the CO 2 injection rate as a variable to better understand its relevance in comparison to the rate constant. As a result, the final uncertainty analysis includes the same set of kinetic parameters for calcite, dolomite, and quartz, along with the percentage of calcite in the initial rock and the initial brine pH.…”

“…The absence of in situ conditions in laboratory experiments, specifically the lack of pore structure contributions, as seen in real storage projects, also contributes to potential inaccuracies when measuring the kinetic parameters of mineral reactions. Overall, predicting in situ reaction rates remains highly complex [5][6][7][8][9] and has prompted researchers to use proxy [10,11] and batch models [12] or analytical approaches [13] to evaluate the geochemical impact.…”

“…A particular focus is on understanding the reactions involving carbonate minerals and the crucial parameters that govern these reactions. This study uses a stochastic approach to model the kinetic parameters, which is different from other studies conducted in the literature, which either model the geochemical reactions deterministically [11,25,26] or neglect them altogether [27,28].…”