Search

Expandable clay minerals play a pivotal role in the geological sequestration of greenhouse gases due to their contribution to storage capacity and caprock integrity. The charge-balancing cations in the interlayer space are known to influence carbon dioxide adsorption. The present study investigated the general adsorption behaviour and characteristics of montmorillonite towards CO2 adsorption at temperatures above critical point, typical to geological sequestration. Modelling on the excess isotherm and absolute isotherm was used to compare the variation of the adsorption behaviour of sodium, potassium and calcium montmorillonite. Excess isotherm modelling using the monolayer Ono-Kondo (O-K) model successfully captured the experimental adsorption. The lateral interaction of the adsorbed molecules on the montmorillonite surface, a variable with the type of cation, remarkably affected the strength of adsorption. The derived adsorbed phase density data confirmed the onset of swelling in montmorillonite at pressures below the critical point. Additionally, the study comprehended the influence of approximations used to derive the absolute isotherm from the experimental isotherm and investigated the validity of common theoretical models to represent adsorption. The study recommended the application of Dubinin-Astakhov (D-A) isotherm with reciprocal van der Waals density approximation or liquid density approximation to model the adsorption of CO2 on montmorillonite. [ABSTRACT FROM AUTHOR]

Geological sequestration of carbon dioxide (CO2) is an effective method to reduce greenhouse gases and an important technology for carbon neutralization. Among all geological sequestration sites, coal reservoirs are potentially effective and practicable. The Xiangzhong Depression of Hunan Province of China is selected as the research area, and the coal seam of Longtan Formation is the target reservoir in this paper. CO2‐enhanced coalbed methane (CO2‐ECBM) and CO2 sequestration capacity are both simulated according to the laboratory experiments on reservoir parameters. During simulation, four production wells and one injection well were designed, and the simulation process can be divided into two stages: CO2‐ECBM and CO2 geological storage. The CO2‐ECBM stage refers to CO2 injection for increasing methane production, and the CO2 geological storage stage aims to predict the CO2 sequestration capacity. After that, sensitivity analyses of sequestration effect are carried out. During the simulation, when maintaining a constant pressure injection of CO2 under the original conditions of 0.01 mD permeability, 9% porosity, and 1.47 MPa reservoir methane pressure, the total storage amount is only 0.14 × 106 m3. However, the storage amount increases significantly to 6.62 × 106 m3 if the permeability increases to 1.5 mD. Orthogonal simulation indicates that permeability has the greatest impact on CO2 sequestration. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mineral carbonation or mineralization of CO2 using rocks or waste industrial materials is emerging as a viable carbon capture and storage (CCS) technology, especially for smaller and medium-scale emitters where geological sequestration is not feasible. During mineralization processes, CO2 chemically reacts with alkaline earth metals in waste materials or rocks to form stable and non-toxic carbonates In situ mineral carbonation holds promise due to ample resources and enhanced security. However, it is still in its early stages, with higher transport and storage costs compared to geological storage in sedimentary basins. Ex situ mineral carbonation has shown promise at pilot and demonstration scales, but its widespread application is hindered by high costs, ranging from US$50-US$300/ton of sequestered CO2. This review delves into the current progress of proposed mineralization technologies and their potential in reducing the overall cost of CO2 sequestration. The discussion critically analyzes various factors affecting carbonation reactions, such as temperature, pressure, leaching agents, solid-to-liquid ratio, and mineralogy for geological settings relevant to the Middle East and the net-zero strategy established within Gulf Cooperation Countries (GCC). Furthermore, the potential commercialization of mineral carbonation, emphasizing the importance of reducing energy consumption and production costs to make the process economically viable is highlighted, offering directions for circular economy and mineral carbonation as a substantial carbon mitigation tool in the Middle East region. Life Cycle Assessment and Techno-Economic Analysis) was also reviewed to provide a comprehensive understanding of both the environmental and economic implications of a CO2 capture via subsurface mineralization

China is a country in the world with the serious environmental pollution of coal mine “three wastes” (solid, liquid, gas). A lot of in-depth research and practice has been carried out on the utilization and treatment of “three wastes”. However, there are still many problems such as imperfect standards and norms, small scale of treatment and unsound technology. In order to solve the problem of synergistic development of low-cost geological storage of large-scale “three wastes” and ecological environment in China’s coal mines, on the basis of the definition of geological storage in other countries, the connotation of geological storage in China has been expanded. The progress and current status of research on the geological storage of “three wastes” are analyzed. Literature and patents related to the geological storage of “three wastes” at home and abroad are reviewed. The problems faced by China in carrying out the geological storage of “three wastes” and the suggestions for further development are put forward. It is pointed out that the main problem faced by the geological storage of “three wastes” in China is the inadequacy of the standards and regulations in the field of environment, especially the extensive lack of standards for the deep-well injection of waste liquids. The systematic research has shown that the research institutions in China are paying increasing attention to research in the field of the geological storage of the “three wastes”, and that the results of the research account for a high percentage of research in the world. China’s coal mine “three wastes” geological storage and ecological environment synergistic development awareness and system is being formed. However, there is insufficient support for research on the large-scale geological storage of “three wastes”, the cyclic system of geological storage of “three wastes” in the whole cycle of coal mining, and the synergistic relationship between CO2 capture, utilization and storage (CCUS) technology and the ecological environment. This seriously restricts the large-scale implementation and application of the concepts, technologies and projects of geological storage. China should expeditiously strengthen the scientific and technological research and development of coal mine “three wastes” geological storage technology and ecological environment synergistic development. Through the establishment of improved standards and norms, increased technological research and development, and strengthened environmental supervision and other measures, the green and sustainable development in China’s coal mines is promoted, helping the China’s “dual-carbon” goal to be realized.

Many studies anticipate that carbon capture and sequestration (CCS) will be essential to decarbonizing the U.S. economy. However, prior work has not estimated the time required to develop, approve, and implement a geologic sequestration site in the United States. We generate such an estimate by identifying six clearance points that must be passed before a sequestration site can become operational. For each clearance point (CP), we elicit expert judgments of the time required in the form of probability distributions and then use stochastic simulation to combine and sum the results. We find that, on average, there is a 90% chance that the time required lies between 5.5 and 9.6 y, with an upper bound of 12 y. Even using the most optimistic expert judgements, the lower bound on time is 2.7 y, and the upper bound is 8.3 y. Using the most pessimistic judgements, the lower bound is 3.5 y and the upper bound is 19.2 y. These estimates suggest that strategies must be found to safely accelerate the process. We conclude the paper by discussing seven potential strategies. [ABSTRACT FROM AUTHOR]

Geopolymer materials have garnered considerable interest as one of the most promising eco-friendly inorganic options over the last decade, thanks to their remarkable properties, including mechanical, chemical, and thermal stability, cost-effectiveness, and sustainable synthesis process, enabling their use in numerous high-value applications. Meanwhile, the ever-increasing concentration of CO2 in the atmosphere is an urgent concern for the environment and human health, forcing the development of effective CO2 capture, storage, and transformation strategies. Various potential solutions for reducing carbon emissions have emerged with the advancement of novel materials and technologies for CO2 capture from exhaust streams and air. Concurrently, significant studies have been conducted on utilizing geopolymers as a sustainable material for CO2 capture. This review provides a comprehensive overview of geopolymers' recent advances and obstacles for CO2 management. We focus on state-of-the-art geopolymer foams and their composites, highlighting their potential for capturing CO2. In addition, we review the use of geopolymers as catalysts or precursors for converting CO2 into value-added chemicals and their potential for geological CO2 sequestration. Moreover, we analyze the current limitations and opportunities for further development of geopolymers in CO2 management. The review provides a perspective on the role of geopolymers in mitigating CO2 effects on the environment and advancing a sustainable future.

Understanding material composition and pore structure variation of shale gas reservoir in the process of supercritical CO2 (scCO2)–brine–shale reaction is of essence to achieve CO2 sequestration and enhanced natural gas production. In this study, shale sample was saturated with 5% NaCl brine to conduct scCO2 reaction experiments under 10 MPa and 333 K using a high-pressure batch reactor. Mineralogical composition, element content, surface morphology and gas adsorption features before and after reaction with scCO2 were measured. According to the results, dissolution of calcite and clay mineral occurred throughout the reaction and carbonate precipitation started as the reaction time exceeded 18 days. The rise of Ca2+ and K+ concentration occurred before 6 days, with moderate increase thereafter. Dissolution enlarged the mesopores and micropores, whereas precipitation only reduced the increasing trend of mesopores, especially for a reaction of 18 days or more. Based on calculations using the CO2 storage and adsorption potential equation, the storage capacity can be enhanced by 4 to 5 times after reaction, which was predominantly controlled by micropores. Compared to the volumetric enlargement of mesopores, the enhanced micropore uptake was associated with its increased number and volume. Therefore, it is more accurate to evaluate the adsorption capacity based on micropore filling during scCO2 reaction. Investigating storage space variation and thus understanding the trapping capacity during CO2 sequestration is a matter of concern for "Carbon Neutrality." [ABSTRACT FROM AUTHOR]

Carbon capture utilization and storage (CCUS) technologies are regarded as an economically feasible way to minimize greenhouse gas emissions. In this paper, various aspects of CCUS are reviewed and discussed, including the use of geological sequestration, ocean sequestration and various mineral carbon mineralization with its accelerated carbonization methods. By chemically reacting CO2 with calcium or magnesium-containing minerals, mineral carbonation technology creates stable carbonate compounds that do not require ongoing liability or monitoring. In addition, using industrial waste residues as a source of carbonate minerals appears as an option because they are less expensive and easily accessible close to CO2 emitters and have higher reactivity than natural minerals. Among those geological formations for CO2 storage, carbon microbubbles sequestration provides the economic leak-free option of carbon capture and storage. This paper first presents the advantages and disadvantages of various ways of storing carbon dioxide; then, it proposes a new method of injecting carbon dioxide and industrial waste into underground cavities. [ABSTRACT FROM AUTHOR]

A tremendous amount of fossil fuel is utilized to meet the rising trend in the world's energy demand, leading to the rising level of CO2 in the atmosphere and ultimately contributing to the greenhouse effect. Numerous CO2 mitigation strategies have been used to reverse this upward trend since large-scale decarbonization is still impractical. For multiple reasons, one of the optimal and available solutions is the usage of old depleted oil and gas reservoirs as objects for prospective CO2 utilization. The methods used in CO2 underground storage are similar to those used in oil exploration and production. However, the process of CO2 storage requires detailed studies conducted experimentally and numerically. The main goal of this paper is to present an overview of the existing laboratory studies, engineering and modeling practices, and sample case studies related to the CCS in oil and gas reservoirs. The paper covers geological CO2 storage technologies and discusses knowledge gaps and potential problems. We attempt to define the key control parameters and propose best practices in published experimental and numerical studies. Analysis of laboratory experiments shows the applicability of the selected reservoirs focusing on trapping mechanisms specific to oil and gas reservoirs only. The current work reports risk control and existing approaches to numerical modeling of CO2 storage. We also provide updates on completed and ongoing CCS in oil and gas reservoir field projects and pilots worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pro 8 increases the internal nanoemulsion pressure and improves CO 2 solubility. • Pro 8 molecule enhances the interaction energy between CO 2 and water to 968 kJ/mol. • Pro 8 extends the aggregation time by 23 % relative to conventional surfactants. Carbon dioxide capture, utilization, and storage (CCUS) technology stands as a highly effective strategy for mitigating carbon dioxide emissions. However, concerns regarding the safety of geological sequestration have impeded the widespread adoption of CCUS. The nano-emulsion, characterized by its diminutive size and exceptional stability, emerges as a prime candidate for CO 2 storage applications. A molecular dynamics investigation into the impact of trisiloxane surfactants on the stability of supercritical CO 2 nano-emulsion revealed that polyglycerol-modified hydrophilic chains engage in hydrogen bonding with water, while siloxane groups exhibit a propensity to penetrate the CO 2 nano-emulsion. Specifically, the Pro 8 molecule enhances the interaction energy between CO 2 and water to approximately 968 kJ/mol, thereby extending the nano-emulsion's aggregation time by 23 % relative to conventional surfactants. The Pro 8 molecule demonstrates an auspicious equilibrium between hydrophilicity and CO 2 affinity, marking it as a superior surfactant for the generation of CO 2 nano-emulsion and underscoring its significant potential for CCUS applications. [ABSTRACT FROM AUTHOR]

Carbon capture utilization and storage (CCUS) technologies are regarded as an economically feasible way to minimize greenhouse gas emissions. In this paper, various aspects of CCUS are reviewed and discussed, including the use of geological sequestration, ocean sequestration and various mineral carbon mineralization with its accelerated carbonization methods. By chemically reacting CO2 with calcium or magnesium-containing minerals, mineral carbonation technology creates stable carbonate compounds that do not require ongoing liability or monitoring. In addition, using industrial waste residues as a source of carbonate minerals appears as an option because they are less expensive and easily accessible close to CO2 emitters and have higher reactivity than natural minerals. Among those geological formations for CO2 storage, carbon microbubbles sequestration provides the economic leak-free option of carbon capture and storage. This paper first presents the advantages and disadvantages of various ways of storing carbon dioxide; then, it proposes a new method of injecting carbon dioxide and industrial waste into underground cavities.

One of the most promising means of reducing carbon content in the atmosphere, which is aimed at tackling the threats of global warming, is injecting carbon dioxide (CO2) into deep saline aquifers (DSAs). Keeping this in mind, this research aims to investigate the effects of various injection schemes/scenarios and aquifer characteristics with a particular view to enhance the current understanding of the key permanent sequestration mechanisms, namely, residual and solubility trapping of CO2. The paper also aims to study the influence of different injection scenarios and flow conditions on the CO2 storage capacity and efficiency of DSAs. Furthermore, a specific term of the permanent capacity and efficiency factor of CO2 immobilization in sedimentary formations is introduced to help facilitate the above analysis. Analyses for the effects of various injection schemes/scenarios and aquifer characteristics on enhancing the key permanent sequestration mechanisms is examined through a series of numerical simulations employed on 3D homogeneous and heterogeneous aquifers based on the geological settings for Sleipner Vest Field, which is located in the Norwegian part of the North Sea. The simulation results highlight the effects of heterogeneity, permeability isotropy, injection orientation and methodology, and domain-grid refinement on the capillary pressure–saturation relationships and the amounts of integrated CO2 throughout the timeline of the simulation via different trapping mechanisms (solubility, residual and structural) and accordingly affect the efficiency of CO2 sequestration. The results have shown that heterogeneity increases the residual trapping of CO2, while homogeneous formations promote more CO2 dissolution because fluid flows faster in homogeneous porous media, inducing more contact with fresh brine, leading to higher dissolution rates of CO2 compared to those in heterogeneous porous medium, which limits fluid seepage. Cyclic injection has been shown to have more influence on heterogenous domains as it increases the capillary pressure, which forces more CO2 into smaller-sized pores to be trapped and exposed to dissolution in the brine at later stages of storage. Storage efficiency increases proportionally with the vertical-to-horizontal permeability ratio of geological formations because higher ratios facilitate the further extent of the gas plume and increases the solubility trapping of the integrated gas. The developed methodology and the presented results are expected to play key roles in providing further insights for assessing the feasibility of various geological formations for CO2 storage.

Abstract Geological sequestration of supercritical CO2 (ScCO2) in deep coal seam has been considered as one of the most promising options for reducing greenhouse gas emission. The permeability of a coal seam, a key parameter estimating the CO2 injectivity, determines the success of ScCO2 storage in the deep coal seam. The deep coal seam has a low initial permeability and a further permeability loss induced by the adsorption‐swelling effects of coal during ScCO2 injection. This paper presents a set of measurements on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by ScCO2 injection. The results indicate that the change in anthracite permeability presents a negative exponential decrease with the buried depth increase. The depth of anthracite reservoir increases from 800 to 1400 m, and its permeability will decrease from 4.59 × 10−2 to 8.04 × 10−4 mD. The permeability change induced by ScCO2 injection is the combining effects of temperature, pressure, and adsorption‐swelling, and the permeability change can be described by a negative exponential model during ScCO2 injection to anthracite reservoir in different depths. The loss coefficient of permeability is up to three magnitudes induced by ScCO2 injection to the anthracite reservoir in the depth of 800 m, 2‐3 magnitudes in 1000‐1200 m, and 1‐2 magnitudes in 1400 m. Although the initial permeability of anthracite reservoirs in the same depth exists differences, the permeability loss coefficient almost has the same magnitudes induced by ScCO2 injection. Comparing with the permeability loss coefficient of the anthracite reservoir in different depths, the permeability variation of the shallow coal seam is more sensitive than the deep induced by ScCO2 injection. However, the deep coal seam has a relatively large fracture pressure, so the allowable ScCO2 injection pressure in the deep coal seam is greater than the shallow.

A tremendous amount of fossil fuel is utilized to meet the rising trend in the world’s energy demand, leading to the rising level of CO2 in the atmosphere and ultimately contributing to the greenhouse effect. Numerous CO2 mitigation strategies have been used to reverse this upward trend since large-scale decarbonization is still impractical. For multiple reasons, one of the optimal and available solutions is the usage of old depleted oil and gas reservoirs as objects for prospective CO2 utilization. The methods used in CO2 underground storage are similar to those used in oil exploration and production. However, the process of CO2 storage requires detailed studies conducted experimentally and numerically. The main goal of this paper is to present an overview of the existing laboratory studies, engineering and modeling practices, and sample case studies related to the CCS in oil and gas reservoirs. The paper covers geological CO2 storage technologies and discusses knowledge gaps and potential problems. We attempt to define the key control parameters and propose best practices in published experimental and numerical studies. Analysis of laboratory experiments shows the applicability of the selected reservoirs focusing on trapping mechanisms specific to oil and gas reservoirs only. The current work reports risk control and existing approaches to numerical modeling of CO2 storage. We also provide updates on completed and ongoing CCS in oil and gas reservoir field projects and pilots worldwide.

CO2 is one of the key greenhouse gases that cause climate change and various ways are being explored to curb CO2 emission in the atmosphere. Mineral carbonation method is one such technique to capture atmospheric CO2 and store it in a carbon sink. However, due to the high cost, the mineral sequestration process is preferred for small emitters (>2.5 Mt CO2). In this study, the mineral carbonation is explored to study its effectiveness in the process of CO2 sequestration. Further, the use of CO2 as a feedstock in the production of different industrial chemicals is explored. In the end, the efficacy of the mineral carbonation process in combating climate change is analyzed.

Geological sequestration of supercritical CO2 (ScCO2) in deep coal seam has been considered as one of the most promising options for reducing greenhouse gas emission. The permeability of a coal seam, a key parameter estimating the CO2 injectivity, determines the success of ScCO2 storage in the deep coal seam. The deep coal seam has a low initial permeability and a further permeability loss induced by the adsorption‐swelling effects of coal during ScCO2 injection. This paper presents a set of measurements on the permeability changes of anthracite reservoirs in different depths of Qinshui Basin induced by ScCO2 injection. The results indicate that the change in anthracite permeability presents a negative exponential decrease with the buried depth increase. The depth of anthracite reservoir increases from 800 to 1400 m, and its permeability will decrease from 4.59 × 10−2 to 8.04 × 10−4 mD. The permeability change induced by ScCO2 injection is the combining effects of temperature, pressure, and adsorption‐swelling, and the permeability change can be described by a negative exponential model during ScCO2 injection to anthracite reservoir in different depths. The loss coefficient of permeability is up to three magnitudes induced by ScCO2 injection to the anthracite reservoir in the depth of 800 m, 2‐3 magnitudes in 1000‐1200 m, and 1‐2 magnitudes in 1400 m. Although the initial permeability of anthracite reservoirs in the same depth exists differences, the permeability loss coefficient almost has the same magnitudes induced by ScCO2 injection. Comparing with the permeability loss coefficient of the anthracite reservoir in different depths, the permeability variation of the shallow coal seam is more sensitive than the deep induced by ScCO2 injection. However, the deep coal seam has a relatively large fracture pressure, so the allowable ScCO2 injection pressure in the deep coal seam is greater than the shallow. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the mechanical behavior of a reservoir is essential for securing the safety of CO2 storage projects. In this study, the effect of CO2-H2O biphasic fluid on the mechanical behavior and failure characteristics of sandstone was revealed. The preliminary results indicate that CO2-H2O biphasic fluid could significantly affect the mechanical behavior of sandstone, including reducing the strength, elastic modulus, Poisson's ratio, and bulk modulus of sandstone; enhancing the bulk compaction; and postponing the onset dilatancy of sandstone. However, the strength of water-bearing sandstone is weakly increased when CO2 is injected into the sample due to the capillary forces that develop under the unsaturated conditions. In addition, CO2-H2O biphasic fluid notably affects the failure characteristics of sandstone at macroand microscales. A complex network of cracks is generated at macrostructure scale. The bonds between particles are damaged by CO2-H2O biphasic fluid at the microstructure scale. [ABSTRACT FROM AUTHOR]

• Proposed a novel workflow for fast and automatic generation of high-performance surrogate flow models. • Integrated simplified neural architecture search (NAS) into surrogate model optimization processes. • Introduced a loss function with variable weight parameters to allow the automatic formation of a suitable loss function. • Evaluated the performance of the surrogate model in different settings by mean relative error. Numerical simulation can significantly enhance subsurface resource utilisation's efficiency and economic benefits by multiphase flow in heterogeneous porous media. However, numerical simulation brings enormous computational demands and time consumption due to high-dimensional nonlinearity, heterogeneity, and coupling of multiple physical processes. Surrogate models can accelerate the establishment of complex models without sacrificing accuracy. However, creating well-performing surrogate models requires extensive human intervention and trial-and-error processes, even for cross-domain experts. This study proposes an automated surrogate flow model workflow based on deep learning called Surrogate Flow Model Search (SFMS). By incorporating neural architectures and loss functions into joint hyperparameter optimisation, SFMS automates many complex and time-consuming tasks involved in model development, such as designing neural architectures and loss functions. The automated surrogate model construction workflow enables researchers to develop high-quality surrogate models without extensive deep-learning expertise. We demonstrate the effectiveness of SFMS using saline aquifer CO 2 injection as an example. The results show that SFMS can automatically generate a highly accurate surrogate flow model in a short time (<1300 s), capable of accurately predicting 120-time steps under different well controls and placements with a low average relative error (<0.4%). Therefore, SFMS can significantly reduce the time and effort required to develop accurate and reliable surrogate models, providing a new approach to building surrogate models. [ABSTRACT FROM AUTHOR]

Geological sequestration represents a promising strategy for storing C O 2. In order to further elucidate this process, we simulated the dissolution-driven convection of a C O 2 -brine system with a free interface in a porous medium, based on a novel Darcy-Cahn-Hilliard model that accounts for the low solubility of C O 2 with brine. We consider a range of unstable Rayleigh numbers Ra , and we derive a quantitative relationship for the dimensionless solute flux. This flux exhibits distinctly different behaviors during the various stages of the flow. In particular, during the free convection stage, larger Ra -values result in a moderate decrease of the solute flux, while the solute flux is approximately independent of Ra during the constant flux stage. In order to evaluate the solute flux during the shutdown stage, we employ simulations in the two-sided Rayleigh-Bénard cell configuration. With a correction factor a =0.67 to account for the damping effect of the bottom boundary, the model can reproduce the solute flux during the shutdown stage. By accounting for the effects of partial miscibility, the simulation approach developed here holds the potential to yield more accurate estimates of the solute flux in the context of C O 2 sequestration and related applications. • A Darcy-Cahn-Hilliard model was employed for low solubility binary flows simulation in porous media • 5 stages of the evolution of the solute flux for CO 2 into brine was analyzed • The solute flux was scaled for the accurate estimates of the storage quantity [ABSTRACT FROM AUTHOR]

Geopolymer materials have garnered considerable interest as one of the most promising eco-friendly inorganic options over the last decade, thanks to their remarkable properties, including mechanical, chemical, and thermal stability, cost-effectiveness, and sustainable synthesis process, enabling their use in numerous high-value applications. Meanwhile, the ever-increasing concentration of CO 2 in the atmosphere is an urgent concern for the environment and human health, forcing the development of effective CO 2 capture, storage, and transformation strategies. Various potential solutions for reducing carbon emissions have emerged with the advancement of novel materials and technologies for CO 2 capture from exhaust streams and air. Concurrently, significant studies have been conducted on utilizing geopolymers as a sustainable material for CO 2 capture. This review provides a comprehensive overview of geopolymers' recent advances and obstacles for CO 2 management. We focus on state-of-the-art geopolymer foams and their composites, highlighting their potential for capturing CO 2. In addition, we review the use of geopolymers as catalysts or precursors for converting CO 2 into value-added chemicals and their potential for geological CO 2 sequestration. Moreover, we analyze the current limitations and opportunities for further development of geopolymers in CO 2 management. The review provides a perspective on the role of geopolymers in mitigating CO 2 effects on the environment and advancing a sustainable future. [Display omitted] • The study an up-to-date review on recent advances in geopolymers for CO 2 management. • It highlights the potential of geopolymer foam and their composites for CO 2 capture. • Geopolymers are also used for catalytic conversion or geologic sequestration of CO 2. • It explores limits and prospects of geopolymers in CO 2 management. • Geopolymer use is a low-cost, greener, and effective option for CO 2 management. [ABSTRACT FROM AUTHOR]

Many studies anticipate that carbon capture and sequestration (CCS) will be essential to decarbonizing the U.S. economy. However, prior work has not estimated the time required to develop, approve, and implement a geologic sequestration site in the United States. We generate such an estimate by identifying six clearance points that must be passed before a sequestration site can become operational. For each clearance point (CP), we elicit expert judgments of the time required in the form of probability distributions and then use stochastic simulation to combine and sum the results. We find that, on average, there is a 90% chance that the time required lies between 5.5 and 9.6 y, with an upper bound of 12 y. Even using the most optimistic expert judgements, the lower bound on time is 2.7 y, and the upper bound is 8.3 y. Using the most pessimistic judgements, the lower bound is 3.5 y and the upper bound is 19.2 y. These estimates suggest that strategies must be found to safely accelerate the process. We conclude the paper by discussing seven potential strategies., Competing Interests: Competing interests statement:The authors declare no competing interest.

Highlights • Characteristics of pore structure of marine and terrestrial shales were studied. • Effects of CO 2 phase states on pore structure characteristics were discussed. • Reactions of subcritical CO 2 with shales decreased the pores at all diameter scales. • Changes differed for marine and terrestrial shales under supercritical CO 2 condition. Abstract To better understand and implement the CO 2 sequestration project, it is of significance to investigate the interaction of shales with CO 2 and its potential effects on the pore morphology. In this study, two marine shale samples and two terrestrial shale samples were prepared and treated with subcritical CO 2 (30 ℃ and 5 MPa) and supercritical CO 2 (80 ℃ and 20 MPa) in a geochemical reactor. Various methods, including low-pressure carbon dioxide adsorption (LP-CO 2 A), low-pressure nitrogen adsorption (LP-N 2 A), high-pressure mercury intrusion porosimetry (HP-MIP) and fractal theory, were used to gain insights into the changes in the shale pore structure after 14 days of CO 2 saturation. According to the results, the phase states of CO 2 obviously affected the variations of pore structure parameters during the physical and chemical reactions in shales. Interactions of supercritical CO 2 with shales created a more obvious effect on the pore structure compared to those of subcritical CO 2 , which was attributed to the greater dissolution and expansion effect as well as the extraction mechanism associated with supercritical CO 2. After exposing the shale samples to subcritical CO 2 , the pore size distributions (PSDs) of the treated shale samples were lower than those of the raw samples at all diameter scales, indicating that the number of pores decreased due to the reactions. Furthermore, it was found that after supercritical CO 2 treatment, the micropore and mesopore structure parameters of the marine shale samples obviously decreased with an increase in macropore structure parameters, leading to the reduction in fractal dimensions in smaller pores, while the terrestrial shale samples appeared to represent a contrary trend. These findings will provide experimental evidence for further assessment of the mechanisms for CO 2 geological sequestration with enhanced shale gas recovery. [ABSTRACT FROM AUTHOR]

This paper describes modeling studies assessing the feasibility of increasing the maximum storage pressure in several underground natural gas storage reservoirs. This required an assessment of the potential for gas transport in the caprock and the geomechanical response to pressure change in the storage reservoir. To solve this problem in an efficient manner, two-phase flow (TOUGH2) and geomechanical (FLAC3D) models were combined in series. The TOUGH2 model was calibrated to fit pressure data collected on-site, from both the reservoir and caprock. The mechanical response of the caprock to increased storage pressure was modeled using FLAC3D, allowing assessment of the induced stresses in formations surrounding the reservoirs. We focused on two sites. In the first, field data were obtained from a deep borehole above the gas reservoir, which provided indirect observations of the geomechanical response of the caprock to pressure changes in the reservoir. In the second, open boreholes intersecting two thin caprock units immediately above the reservoir allowed gas flow to a shallower unit, significantly impacting the modeled fracture gradient. [ABSTRACT FROM AUTHOR]

This paper describes the CO 2 geological sequestration process in unconventional reservoirs in northern and southern United States such as Bakken tight oil and Eagle Ford shale gas condensate reservoirs. The hysteresis modelling and retention mechanism was performed in this research and this is one of the efficient and proven method to store CO 2 in the subsurface. This can be achieved through CO 2 EOR process while injecting CO 2 , the fluid will be trapped in the pore spaces between the impermeable rocks and oil can be recovered simultaneously. A total of four cases was taken for the analysis, such as the Bakken and Eagle Ford reservoirs with CO 2 huff-n-puff process and another two cases with CO 2 Flooding. Injection pressure, injection rate, injection time, number of cycles, carbon dioxide soaking time, fracture half-length, fracture conductivity, fracture spacing, porosity, permeability, and initial reservoir pressure as is taken as inputs and cumulative oil production, and oil recovery factor was taken as outputs. The reservoirs were modelled for 30 years of oil production and the factor year was taken as Decision Making Unit (DMU) and the models was calculated at each year. The retention was successfully calculated in all four models and percentage of retention above 90% was observed in all four cases and the injection pressure has the most dominating effect on the CO 2 geological sequestration. It was also revealed that the CO 2 huff-n-puff performance in Bakken reservoir is not that much more effective since the retention rate decreases during soaking period and flooding was found to be a suitable method in this formation. Even in Eagle Ford formation, the average performance of CO 2 flooding process is better than the huff-n-puff, but the latter process was quite effective in this shale gas condensate reservoir. [ABSTRACT FROM AUTHOR]

A two-phase flow unified pipe network method is developed to simulate CO 2 evolution in fractured saline aquifers. Fractures are explicitly represented in the proposed method. The two-phase flow in both rock matrix and fractures is considered by using different equivalent pipe flow models respectively, namely the two-phase matrix pipe flow model and the two-phase fracture pipe flow model. The equivalent flow coefficients of the pipe flow models are derived based on flow rate equivalence. The coupling of the fracture pipe flow and matrix pipe flow is treated by applying the extended capillary pressure conditions. Brooks-Corey relative permeability model and capillary model are adopted to simulate CO 2 (non-wetting phase) invasion into the brine (wetting phase) saturated formation, which is a typical drainage process. Accurate Equations of State for calculating density and viscosity of CO 2 are incorporated to reflect its change in hydraulic characteristics during the injection processes. The proposed method is simple yet robust and not sensitive to the mesh quality. The complex geological and topological features of fracture networks can, therefore, be well retained in the proposed method. The anisotropy and heterogeneity characteristics of the fractured rock mass caused by the fracture networks can be accurately represented. The proposed method is verified by comparing to other numerical methods. Both 2D and 3D models with complex fracture networks are presented to demonstrate the feasibility of proposed method. Numerical examples show that fractures can significantly affect the distribution and evolution of CO 2 in aquifers and the differences of entry capillary pressures for fractures and matrix rock should be accurately simulated. [ABSTRACT FROM AUTHOR]

Exhumed reservoirs providing evidence of CO 2 accumulation and transport in geological history offer a unique possibility to supplement our knowledge on leakage processes observed along faults and fractures. A field location and drill core from Central Utah, USA has been used to characterize mechanical properties and fracture distributions in multiple reservoir-caprock couplets where bleaching pattern around fractures provides evidence of fluid flow. Analysis shows that fractures are mainly observed in low porosity units corresponding to layers with high strength and stiffness. Microstructural characterization substantiates evidence of fracture aperture separated by areas with mineral precipitation clogging aperture. Minerals observed filling fractures are calcite, gypsum and pyrite, suggestive of precipitation from reducing fluids. Fracture aperture distribution and identification of mineralogical changes along the fracture surface provides important input for improved, novel analyses of CO 2 transport properties of fractures and faults. [ABSTRACT FROM AUTHOR]

To better understand the effects of CO 2 sequestration and long-term storage, it is worth studying the interactions between supercritical CO 2 (SC-CO 2 ) and coal, and its influence on coal properties or, more specifically, the changes in coal pore structure and functional groups caused by SC-CO 2 . In this study, three different metamorphic grades of coal were sampled and exposed to SC-CO 2 (∼40 °C and 10 MPa) for 120 h through a geochemical reactor, simulating CO 2 storage in deep coal seams. The functional groups and pore structure of different coal ranks before and after SC-CO 2 treatment were measured by Fourier Transform Infrared Spectroscopy (FTIR), Mercury Intrusion Porosimetry (MIP) and physical adsorption method. The results show that the absorption peak intensity of –OH groups, with intramolecular association and C–H stretching vibrations, clearly changed for anthracite compared to others. Compounds with weakly polar functional groups, such as hydrocarbons, epoxy and lipid compounds (ether or ester), decreased significantly, whereas strongly polar functional groups exhibited only a slight change. Pore structure and distribution of each pore phase showed the diversity present in different coal ranks. The development of seepage-flow pores (mesopore and macropore) was promoted by SC-CO 2 . For high rank and medium rank coals, the degree of pore development was significantly altered by SC-CO 2 , while pore development in low rank coal was largely unaltered. The results of this study contribute to the understanding of coal structure evolution and its effects on coal reservoir during long-term geological sequestration. [ABSTRACT FROM AUTHOR]