A multiscale algorithm for the mineralization process during supercritical carbon dioxide injection into a deep saline aquifer

Large volumes of carbon dioxide (CO2 ) captured from carbon emission source can be stored in deep saline aquifers as a mean of mitigating climate change. The deep saline aquifers are naturally heterogeneous at multiple scales. It is important to generate representative multiscale heterogeneous fields of various hydrogeologic properties and understand storage safety by studying CO2 migration and distribution in such fields. In this work, a new multiscale heterogeneous model with partly fine multi-facies heterogeneous domain is proposed. A method based on transition probability theory is referred to establish a multi-facies model. A new multiscale heterogeneous model with partly fine multi-facies heterogeneous domain is built up according to the categorized permeability data obtained from the Geological Carbon Storage Frio site in USA. TOUGH2/ECO2N is applied to simulate CO2 migration and distribution in such a multiscale heterogeneous model. The CO2 plume shows obvious viscous fingering and non-uniform migration both in layered and vertical directions, implying vertical and horizontal heterogeneity which cannot be represented by a single-scale model or simulated with the assumption of homogeneous formation. The profile of CO2 migration shown in the numerical simulation at a time of 10 days is in a good accordance with the seismic data of Frio situ in qualitative and quantitative aspects. Cited as: Ren, J., Wang, Y., Feng, D., Gong, J. CO2 migration and distribution in multiscale-heterogeneous deep saline aquifers. Advances in Geo-Energy Research, 2021, 5(3): 333-346, doi: 10.46690/ager.2021.03.08

CO2 sequestration in deep saline aquifers has proven to be one of the most promising options to reduce anthropogenic CO2 emissions. Sedimentary basins are chosen as targets of CO2 sequestration due to the existence of deep saline aquifers. This paper presents the first systematic investigation on the occurrence and characteristics of potential reservoirs for CO2 sequestration in deep saline aquifers in the Bohai Bay Basin (BBB) and offers detailed estimates on the storage capacity within the depth range from 800 to 3500 m. A preliminary suitability assessment for preferential sites is also presented. Geological analyses show that deep saline aquifers in Guantao formation (Ng) of Neogene, Dongying (Ed) and Shahejie formations (Es1, Es2, Es3, Es4) of Paleogene are potential reservoirs. Deep saline aquifers in the BBB may accommodate about 3922 Mt CO2 with 50 % confidence level, according to a modified CSLF (Carbon Sequestration Leadership Forum) method. The CO2 storage capacity of individual depression varies from 65 Mt (Liaohe depression) to 934 Mt (Liaodongwan-Bozhong depression). The Guantao formation (Ng) of Neogene is a regionally distributed reservoir with low TDS (Total Dissolved Solids) and favorable depth and thickness, the capacity of which accounts for 84 % of the total and is therefore considered as the most promising reservoir. Preliminary suitability assessment is carried out in terms of sedimentology, tectonic stability, geothermal conditions, saline water characteristics, potentially conflicting resources development as well as CO2 emission sources. The Liaodongwan & Bozhong, Jiyang & Changwei and Huanghua depressions are chosen as the most suitable sites for CO2 storage. Jizhong and Liaohe depressions are less suitable while Linqing depression is not suitable due to its lower tectonic stability, geological information and CO2 emission sources. Although uncertainties exist, the estimate in this study is significant for future study and implementation of CO2 sequestration in the basin.

Assessing the geological storage potential of CO2 in Baltic Basin: A case study of Lithuanian hydrocarbon and deep saline reservoirs

CO2 storage in saline aquifers: A simulation on quantifying the impact of permeability heterogeneity

Carbon capture and storage (CCS) technology is a crucial and effective tool to achieve China’s dual carbon goals. The primary locations suitable for underground CO2 storage include depleted oil and gas reservoirs, deep saline aquifers, and deep unmineable coal seams. Among these, deep saline aquifers are widely distributed in most of the world’s sedimentary basins, and they offer significant advantages—such as substantial storage capacity, well-established technology, high safety standards, and cost effectiveness—making them crucial geological reservoirs for carbon dioxide storage. In comparison to foreign countries’ projects on CO2 capture, utilization, and storage (CCUS) technology, China’s initiatives have been implemented more recently, and no research has been conducted on the geological storage of CO2 in the deep saline aquifers within the study area. In this study, we systematically analyzed the key factors for the geological storage of CO2 in saline reservoirs within the northwest plain of Shandong Province: the Paleogene Shahejie Formation saline aquifer, and the lower reservoir of the Minghuazhen Formation saline aquifer located east of the Zhanhua–Lijin–Dongying line. The CO2 geological storage potential of these aquifers was assessed using the evaluation methodology of the United States Department of Energy, yielding a result of 30.355 billion tons. An evaluation index system of CO2 geological storage suitability was established. Evaluation indices for regions in the study area were assigned according to this evaluation index, and the score and grade of each unit were obtained. The results indicated that the Huimin latent fault depression, Dongying latent fault depression, Dezhou latent fault depression, and Dongming–Shenxian latent fault depression are suitable prospective areas for CO2 geological storage in the saline aquifers of Shandong Province’s northwest plain.

CO2 storage in deep saline aquifers is considered a possible option for mitigation of greenhouse gas emissions from anthropogenic sources. Understanding of the underlying mechanisms, such as convective mixing, that affect the long‐term fate of the injected CO2 in deep saline aquifers, is of prime importance. We present scaling analysis of the convective mixing of CO2 in saline aquifers based on direct numerical simulations. The convective mixing of CO2 in aquifers is studied, and three mixing periods are identified. It is found that, for Rayleigh numbers less than 600, mixing can be approximated by a scaling relationship for the Sherwood number, which is proportional to Ra1/2. Furthermore, it is shown that the onset of natural convection follows tDc∼Ra−2 and the wavelengths of the initial convective instabilities are proportional to Ra. Such findings give insight into understanding the mixing mechanisms and long term fate of the injected CO2 for large scale geological sequestration in deep saline aquifers. In addition, a criterion is developed that provides the appropriate numerical mesh resolution required for accurate modeling of convective mixing of CO2 in deep saline aquifers. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Prospect for storage of impure carbon dioxide streams in deep saline aquifers—A convective dissolution perspective

Injection of Brine from Cavern Leaching into Deep Saline Aquifers: Long-Term Experiences in Modeling and Reservoir Survey

It has been proved to be one effective means to reduce emissions of CO2 to mitigate the worsening global climate change through lots of projects and tests about CO2 geological storage. The sites that are suitable for CO2 geological storage include coal seams that can not be mined, deep saline aquifers, oil fields, and depleted gas fields. The emission of CO2 from fuel combustion is about 3.54 Gt in China in 2003, which is the second biggest in the world. Because the energy consumption in China mainly depends on fossil fuels for a long time in the future, China will become a country with the biggest emission of COz in the world, which will make China have to reduce the emissions of CO2 by some methods including geological storage. Based on lots of information about the reserves of coal seam methane and the rank of coal in the 68 coal basins in China, the total CO2 storage capacity in these coal basins was estimated according to the recovery coefficient and exchange ratio of CO2 to CH4.The total storage capacity in deep saline aquifers can be regarded as the total quantity of CO2 that can be dissolved in the saline aquifers at the depth from 1000m to 3000m under ground. The quantity can be estimated by multiplying the solubility of CO2 in the saline water and the volume of the appropriate aquifers. According to the reserve and quality of crude oil in 46 main oil basins in China, the CO2 storage capacity and the quantity of enhanced oil were calculated. The storage capacity of depleted gas fields can be derived from the reserve and depth of the gas fields. The total CO2 geological storage capacity is about 196.2 Gt CO2 that is as against 55.4 times the CO2 emission from fuel combustion in China in 2003. According to the results of the finished projects and tests about CO2-EOR and CO2-ECBM, the CO2 geological storage capacities in coal seams, deep saline aquifers, oil fields and depleted gas fields will be estimated. The feasibility of CO2 geological storage in China is assessed according to the storage capacities and the distribution of large-scale emissions of CO2. The results showed that the more feasible sites include North China Plain, Ordos Basin, Qinshui Basin, and Songliao Basin.

Geological CO2 sequestration (GCS) has been a practical approach used to mitigate global climate change. Uncertainty and sensitivity analysis of CO2 storage capacity prediction are essential aspects for large-scale CO2 sequestration. This work presents a rigorous machine learning-assisted workflow for the uncertainty and global sensitivity analysis of CO2 storage capacity prediction in deep saline aquifers. The proposed workflow comprises three main steps: 1) dataset generation — we first identify the uncertainty parameters that impact CO2 storage in deep saline aquifers and then determine their corresponding ranges and distributions. We generate the required data samples by combining the Latin Hypercube Sampling (LHS) technique with high-resolution simulations. 2) surrogate development — a data-driven surrogate is developed to map the nonlinear relationship between the input parameters and corresponding output interests from the previous step. The implementation of Bayesian optimization accelerates the tunning process of hyper-parameters instead of traditional trial-error analysis. 3) uncertainty and global sensitivity analysis — Monte Carlo simulations based on the optimized surrogate are performed to explore the time-dependent uncertainty propagation of model outputs. Then the key contributors are identified by calculating the Sobol indices based on the global sensitivity analysis. The proposed workflow is accurate and efficient and could be readily implemented in field-scale CO2 sequestration in deep saline aquifers.

Geological CO2 sequestration (GCS) has been proposed as an effective approach to mitigate carbon emissions in the atmosphere. Uncertainty and sensitivity analysis of the fate of CO2 dynamics and storage are essential aspects of large-scale reservoir simulations. This work presents a rigorous machine learning-assisted (ML) workflow for the uncertainty and global sensitivity analysis of CO2 storage prediction in deep saline aquifers. The proposed workflow comprises three main steps: The first step concerns dataset generation, in which we identify the uncertainty parameters impacting CO2 flow and transport and then determine their corresponding ranges and distributions. The training data samples are generated by combining the Latin Hypercube Sampling (LHS) technique with high-resolution simulations. The second step involves ML model development based on a data-driven ML model, which is generated to map the nonlinear relationship between the input parameters and corresponding output interests from the previous step. We show that using Bayesian optimization significantly accelerates the tuning process of hyper-parameters, which is vastly superior to a traditional trial–error analysis. In the third step, uncertainty and global sensitivity analysis are performed using Monte Carlo simulations applied to the optimized surrogate. This step is performed to explore the time-dependent uncertainty propagation of model outputs. The key uncertainty parameters are then identified by calculating the Sobol indices based on the global sensitivity analysis. The proposed workflow is accurate and efficient and could be readily implemented in field-scale CO2 sequestration in deep saline aquifers.

Geochemical aspects of CO2 sequestration in deep saline aquifers: A review

The injection of carbon dioxide (CO2) in deep saline aquifer is a forefront strategic method to reduce emissions of CO2 in the atmosphere. CO2 is injected into deep saline aquifer as a supercritical fluid with density and viscosity that is less than the formation brine. This leads to CO2 upwards migration under buoyancy. Existing analytical solution did not account for permeability anisotropy (Kv/Kh) ratio. An analytical and numerical investigation was carried out into the effect of varying Kv/Kh ratios on the position of the CO2-brine interface. Existing analytical solution was then corrected to account for variation in Kv/Kh ratios. ECLIPSE 300 and Amarile’s RE-Studio were used for the pre and post processing modelling and analysis. The result suggests that errors in the interface position (when Kv/Kh variation is not taken into account) is greater when viscosity dominates, but when gravity dominates, the errors are less significant. Numerical simulations agreed with the analytical model because the lowest Kv/Kh model resulted in more lateral extent due to viscosity effect, whereas higher Kv/Kh resulted in vertical migration due to gravity forces. Anisotropic permeability ratios are more important during injection. Analytical and numerical solutions suggest that variation in permeability anisotropy determines CO2 plume evolution.

The current approach to carbon capture and sequestration (CCS) from pulverized coal-fired power plants is not economically viable without either large subsidies or a very high price on carbon. Current schemes require roughly a third of a power plant's energy for carbon dioxide capture and pressurization. The production of energy from geopressured aquifers has evolved as a separate, independent technology from the sequestration of carbon dioxide in deep, saline aquifers. A gamechanging new idea is described here that combines the two technologies and adds another: dissolution of carbon dioxide into extracted brine which is then re-injected. A systematic investigation over a range of conditions was performed to explore the best strategy for the coupled process of CO2 sequestration and energy production. Geological models of geopressuredgeothermal aquifers were developed using available data from studies of Gulf Coast aquifers. These geological models were used to perform compositional reservoir simulations of realistic processes with coupled aquifer and wellbore models. Introduction The sequestration of carbon dioxide and other greenhouse gases in deep saline aquifers (Keith, 2009) as well as the extraction of methane and geothermal energy (heat) from deep geopressured-geothermal aquifers (Jones, 1975) have been studied independently in the past. However, capturing and storing CO2 in aquifers is an expensive process without any monetary return on investment. On the other hand, energy extraction from deep geopressured aquifers was abandoned as a result of low natural gas prices in the 70s and 80s (Griggs, 2005), which prevented this process from becoming economically feasible. In this study, we present a new strategy in which the CO2 sequestration and methane/geothermal energy extraction are combined. In fact, we suggest that the cost of the former can be offset by the profits from the latter. Geologic formations are capable of storing huge amounts of CO2. Specifically, deep saline aquifers are the best candidates for the storage of significant amounts of CO2 emitted by pulverized coal-fired power plants. However, the storage technology faces several constraints. The most important constraint is the cost of the storage process which includes capturing, purifying, pressurizing, and injecting CO2 (Rochelle, 2009). In addition to the storage cost, other possible constraints exist such as the injection capacity of the aquifer and environmental hazards. Formations of abnormally high pressure and temperature lie along the Gulf Coast of the United States at depths exceeding 10,000 feet. The brine in these formations is saturated with methane. The methane content of this brine is on the order of 30- 45 SCF of methane per barrel and the total amount is estimated to be between 3000 to 46000 TCF (Griggs, 2005). For example, at 34 SCF per barrel, a small geopressured aquifer with a pore volume of 1 billion barrels would hold a volume of dissolved methane of 34 BCF with an energy content of 35 trillion Btu. When CO2 is dissolved in brine saturated with methane, almost all of the methane comes out of the solution and forms a gas phase of almost pure methane (Taggart, 2009). The production of this methane could help offset the cost of CO2 storage. Moreover, the production of methane gas and/or brine saturated with methane while CO2 is being injected will reduce or eliminate concerns about pressure build-up accompanying CO2 injection. This pressure build-up is a key constraint on large-scale sequestration, because it significantly reduces achievable rates of CO2 injection.

Development of a linear predictive model for carbon dioxide sequestration in deep saline carbonate aquifers