CO2 Migration Research Articles

Pressure and temperature response and phase transition path during small hole leakage in a near-industrial scale CO2 pipe

ABSTRACT As a large-scale CO2 migration method, pipelines play a crucial role in the CCUS industry chain. Small hole leakage caused by self defects, fatigue and corrosion, and natural disasters is a common accident in CO2 pipelines. When leaked CO2 is sprayed out through a small hole, the temperature inside the pipeline drops sharply under the Joule Thomson effect. This sudden temperature drop significantly reduces the toughness of the material, increases the risk of brittle fracture. In order to improve the CO2 pipeline release database, a new industrial scale CO2 pipeline has been built. The CO2 release experiments were carried out by using this experimental device. The experimental results showed that the pressure drop rate was fast under high pressure and then slowed down when the pressure dropped below the critical pressure, with the coexistence of gas and liquid. Rapid pressure drop and slight rebound occur during the leakage process, and low initial pressure leads to a more pronounced pressure plateau effect. Dense-phase CO2 leakage produced more dry ice than supercritical state, and the far field sublimation effect was more significant. In practice, particular attention should be paid to safety far from the leakage end.

Metal mobilisation and fines migration in pure CO2 and impure CO2-SO2-NO reactions of carbon storage site core.

Carbon dioxide geological storage is proposed as part of the solution to reach net zero emissions. The potential to mobilise heavy metals to low salinity groundwater through CO2 water rock geochemical reactions is a potential environmental risk factor, if CO2 migrates. Previous studies have focused on pure CO2 reactivity, however CO2 streams from hard to abate industries can contain gas impurities. Reservoir sandstone and mudstone drill cores from a proposed low salinity CO2 storage demonstration site were reacted at in situ conditions with pure CO2 or an impure NO-SO2-CO2 stream. Sandstones hosted Rb in illite analysed via synchrotron XFM. Arsenic (As) was hosted in pyrite; and Pb, Cr, Mn in siderite rimming intergranular pores. Mudstone contained Zn, Co, Ni, Cu, As, Pb in sphalerite, and Rb in illite and K-feldspar. In impure NO-SO2-CO2 experiments the lowered pH and oxidising conditions initially released higher concentrations of metals including Pb, Zn, Co into solution compared to pure CO2 reactions. Higher concentrations of Zn (Mn and Co) were released from sphalerite in the mudstone. Fe-chlorite, K-feldspar, and carbonate dissolution released Rb, Si, Fe, Ca, and Mg. Elevated dissolved Pb was mainly from siderite and sulphide mineral reaction in sandstones. Mobilised As was released prior to CO2 addition from desorption and ion exchange. Clay and fines migration into pores occurred in both pure and impure CO2 reactions that has the potential to impact fluid migration. A portion of metals including Fe, Ni, Cr were subsequently incorporated in precipitated Fe hydr(oxy)oxides where the co-injected NO induced oxidising conditions. Rock mineral content and the injected gas mix were the main controls on metal mobilisation to formation water. Further work should investigate new gas mixtures that may be expected in storage hubs, from blue hydrogen or from direct air capture.

Influence of cobalt substitution in CoFe2O4 nanoparticles on structural, morphological, cation distribution, optical and magnetic properties.

This paper presents the first-time synthesis of CoFe Co x O4 nanoparticles (where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) through hydrothermal methods utilizing metal chloride precursors. X-ray diffraction (XRD) analysis confirms the formation of a cubic spinel structure characterized by the Fd m space group. Field Emission Scanning Electron Microscopy (FE-SEM) images reveal that the average grain size of the nanoparticles lies between 50 nm and 90 nm. Notably, the optical band gap of the Co3+-doped samples exhibits a gradual increase from 1.7 eV to 2.5 eV. Furthermore, a reduction in saturation magnetization was noted with increasing doping content at both 5K and 300K. The observed decrease in saturation magnetization in the doped samples can be attributed to the migration of Co2+ ions from the B site to the A site, as well as the substitution of Fe3+ ions with Co3+ ions in the B site. Additionally, the influence of annealing temperature on the structure, morphology, and magnetic properties of the nanoparticles was examined.

Improving CO2 storage efficiency in saline aquifers through wettability-optimized nanoparticle foam

The sequestration of CO2 in saline aquifers represents a critical strategy for mitigating the warming effects of greenhouse gases. Nanoparticle foams, known for their superior stability, are instrumental in substantially reducing the CO2 migration rate. This makes their use a promising method for the geological containment of CO2. In this paper, the utilization of nanoparticle foam in the geological storage of CO2 was investigated. By combining nanoparticles with six different wettability characteristics and five types of cationic surfactants, the optimal contact angle range for surfactant compatibility was determined. Additionally, the impact of nanoparticle wettability on foam performance and rheological behavior was evaluated. Ultimately, displacement experiments were conducted to investigate how nanoparticle foams can enhance the CO2 storage capabilities of geological formations. The experimental results show that the primary contact angle of nanoparticles plays a crucial role in determining their compatibility with cationic surfactants. Nanoparticles are found to be most effective within a contact angle range of 37.83°–51.13°. In displacement experiments, foam DDA (ethyl dodecyl dimethyl ammonium chloride) reaches its maximum CO2 geological sequestration capacity at a foam quality of 80%. In contrast, foam produced by surfactant DDA and nanoparticle N20 (DDA+N20) achieved the highest CO2 sequestration capacity at 85% foam quality. Distinctively, compared with traditional foams, foam DDA+N20 exhibits superior capabilities, storing more CO2 while consuming less water. The outcomes of these experiments provide invaluable directions for the application of nanoparticle foams in geological CO2 sequestration endeavors.

Study on CO migration characteristics after blasting in tunnel under different ventilation methods

ABSTRACT Tunneling and blasting generate blasting smoke, containing high concentrations of toxic gases like CO and NOx, and dust. Prolonged CO presence in tunnels can harm workers. CO discharge in tunnels is influenced by ventilation methods and parameters. However, limited research exists on how ventilation parameters like the distance between the duct opening and the tunnel excavating face and the pressure extraction ratio affect CO levels. This paper uses Computational Fluid Dynamics (CFD) to simulate and analyze these parameters’ impact on CO migration after blasting in excavation roadways. Results show that under forced ventilation, CO migration speed is inversely proportional to the distance from the duct opening to the tunnel excavating face, with the best removal effect at 3 meters, reducing CO to a safe level in 170–180 seconds. Under exhaust ventilation, the closer the duct opening to the tunnel excavating face, the faster the CO migration, with the best removal effect at 1 meter, reducing CO to a safe level in 100–110 seconds. In mixed ventilation, different pressure extraction ratios significantly affect CO migration. With a constant press-in air volume, a pressure extraction ratio of 0.8 most effectively promotes CO migration, reducing CO to a safe level in 120–130 seconds.

Impact of Relative Permeability Hysteresis on CO2 Storage in Saline Aquifers

ABSTRACTThe urgent challenge of climate change, driven by rising carbon emissions, necessitates innovative strategies for carbon capture and storage (CCS). This study examines the impact of hysteresis in relative permeability on CO2 entrapment efficiency within saline aquifers, known for their significant storage capabilities. An aquifer model was analyzed through numerical simulation by varying hysteresis values from 0.2 to 0.5 to evaluate their impact on CO2 plume behavior, retention during water‐alternating‐gas (WAG) injection, and plume morphology. The CO2 plume exhibits a funnel‐shaped configuration at low hysteresis with a narrow, pointed base, indicating a concentrated upward migration trajectory. In contrast, a hysteresis value of 0.5 results in diminished gas movement toward the upper aquifer, transforming the plume into a more oval shape. Results from the land trapping model further support our findings, revealing an inverse relationship where increased hysteresis enhances residual CO2 entrapment, reflected in trapping coefficient values ranging from 0.5 to 4. This underscores the model's efficacy in verifying gas trapping efficiency and safety during sequestration. Moreover, increased water flow generates stronger forces, pushing CO2 into narrower pore spaces, where it becomes trapped. Our findings indicate that increased hysteresis enhances CO2 retention by limiting vertical migration and significantly influences plume geometry, promoting stable and predictable distribution patterns. At higher hysteresis values, CO2 migration is significantly restricted, resulting in near‐complete immobilization of the injected gas. This research highlights hysteresis's critical role in refining injection methodologies and enhancing plume stability for long‐term CO2 storage. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Integrated Three-Dimensional Structural and Petrophysical Modeling for Assessment of CO2 Storage Potential in Gas Reservoir

Abstract Carbon dioxide (CO2) storage in oil and gas reservoirs is one of the most effective methods for enhancing hydrocarbon recovery efficiency and mitigating climate change by securely storing CO2. However, building a realistic three-dimensional (3D) geological model for these storage reservoirs poses a significant challenge. To address this, employing a novel methodology combining 3D structural and petrophysical modeling, our study presents a pioneering effort to assess the CO2 storage potential of the faulted reservoir between the G- and E-sands of the Lower Goru Formation in the Kadanwari Gas Field (KGF), Middle Indus Basin (MIB), Pakistan. Analysis of seismic data revealed a complex reservoirs structure affected by normal faults oriented in a northwest–southeast direction. These faults partition the reservoir into several compartments and could serve as potential pathways for CO2 migration. Three-dimensional structural modeling unveiled complex features, for example horsts, grabens, and half-grabens, formed through multiple deformation stages. Petrophysical modeling indicated promising reservoir characteristics, that is high porosity and permeability in the desired zone. Three-dimensional property models were generated using sequential Gaussian simulation to represent the distribution of petrophysical properties, for example porosity, permeability, shale volume, and water saturation. Geological uncertainties were incorporated enabling the calculation of pore volume distribution and corresponding uncertainty. A novel technique was developed to assess the probable CO2 storage potential in the KGF, considering its distinctive features. The study revealed a storage potential ranging from 10.13 million tons (P10) to 101.54 million tons (P90), with an average potential of 53.58 million tons (P50). Our study offers a comprehensive approach to evaluating CO2 storage potential in complex geological zones, filling a knowledge gap in existing literature on carbon neutrality efforts in Pakistan. These findings lay the groundwork for future initiatives in geological CO2 storage in the MIB and support the country’s efforts to reduce carbon emissions.

Numerical Analysis of Gas Generation and Migration in a Radioactive Waste Disposal Cell of a Deep Geological Repository

Abstract In a deep geological repository (DGR) for the long-term disposal of radioactive waste, gases (e.g., hydrogen (H2), carbon dioxide (CO2) and methane (CH4)) can be generated through a number of processes, such as corrosion of various metals and alloys and degradation of organic materials. If gas induced pressure exceeds the containment capacity of the engineered barrier systems (EBS) or the host rock, the gases could migrate through these barriers and potentially expose people and the environment to radiation. Therefore, a good understanding on the long-term performance of these barriers against gas migration is an important component in DGR design and safety assessment. In the present work, a numerical model has been developed to simulate the diffusion of CO2 (one of the gas species) in the near field of a DGR with the generation from related chemical reactions. The generation of CO2 was investigated to determine if it is a critical factor to impact the DGR safety under Canadian geological formations. A commercial computational fluid dynamics (CFD) code, ANSYS Fluent was used for the calculations. The model considered pH and temperature effects on CO2 migration under Canadian DGR geochemistry conditions.

Numerical Modelling of CO2 Injection and Storage in Low Porosity and Low Permeability Saline Aquifers: A Design for the Permian Shiqianfeng Formation in the Yulin Area, Ordos Basin

The geological storage of CO2 in saline aquifers is a crucial method for achieving large-scale carbon storage in the future. The saline aquifers with low porosity and permeability in the Ordos Basin exhibit high irreducible water saturation and restricted fluid mobility, necessitating further investigation of their injectivity and storage safety. The fifth member of the Shiqianfeng Formation (P3sh5) in the Ordos Basin serves as a key layer for geological CO2 storage (GCS). The numerical simulation of CO2 injection in this reservoir is an indispensable process for characterizing the migration and storage of CO2. Injection pressure and well type (vertical well or horizontal well) are critical factors affecting GCS. The results of the numerical simulation are important preliminary preparations for promoting the GCS in the saline aquifer of the Shiqianfeng Formation in the future. This paper focuses on P3sh5 in the Yulin area as a case study. It investigates the injectivity and CO2 migration characteristics of these low porosity and low permeability saline aquifers in the Ordos Basin. Relatively high-quality distributary channel sandstone bodies in integrally low porosity and permeability strata were identified for injection. As CO2 is injected, the formation pressure gradually increases. It is essential to maintain it below the fracture pressure during CO2 injection to ensure safety. High-pressure (8 MPa) injection could achieve volumes 2.9 times greater than those in the low-pressure scenario (4 MPa) of 2 km horizontal branch well. Under the three injection well types, the injection rate of vertical wells is the lowest. Employing a “horizontal branch well injection” strategy could potentially amplify the injection volume by 2.87 times. CO2 predominantly migrates vertically near the horizontal interval of interest, while horizontally, the area near the interval of interest experiences a higher CO2 saturation, with the maximum saturation reaching about 50%. Overall, CO2 is migrated in the distributary channel sandstone bodies, indicating a higher storage safety and lower leakage risk. It is recommended that the number of drilling wells be increased and multiple horizontal branch wells implemented to enhance the injection efficiency. Overall, this study provides a geological foundation for the previous design and construction of the GCS project in the Ordos Basin’s saline aquifer. It also provides a reference for GCS in low permeability saline layers in similar regions worldwide.

Temperature Effects on the Surface Dynamics of the CO2 Reduction Reaction over Copper

The electrochemical reduction of CO2 (CO2RR) has stood out as a pathway to mitigate carbon emissions and supply multi-carbon feedstocks to the chemical industry. While most CO2RR studies over copper are carried out at room temperature, heat transfer limitations in the electrolyte will result in temperature buildup near the electrode in industrial CO2 electrolyzers. Reaction temperature plays a key role in the reaction activity and product selectivity by controlling the distribution of species on the copper surface. In this study, we use surface enhanced infrared absorption spectroscopy (SEIRAS) and surface enhanced Raman spectroscopy (SERS) to investigate the effect of temperature on the dynamics of reactive intermediates in the reaction microenvironment (Fig. A).Using SEIRAS, we showed site-specific CO coverage is dependent on temperature, and how CO migration seems to directly impact product distribution at higher temperatures. We found that increasing temperature leads to decreased CO and increased alkyl groups coverage for a given potential (Fig. B). This suggests that temperature has a direct effect on the selection of mechanistic pathways in the conversion of CO to C1 and C2 products, beyond just controlling mass transport and local CO2 availability. Using SERS, we showed that the local pH is considerably higher than their bulk values, and that higher temperatures consistently led to higher local pH values (Fig. C). The significant depletion of local hydrogen with increasing temperature indicates that local pH plays a key role in driving reaction selectivity dependence on temperature. Understanding the effect of temperature on the CO2RR surface dynamics through surface sensitive techniques is a key step to rationalize product distribution and to design solutions for enhanced C2+ production in industrial CO2 electrolyzers. Figure 1

Fast mass transfer processes of interfering trapped CO2-clusters at reservoir conditions: Experiment and theory

The gas-to-oil ratio (GOR) of a reservoir fluid plays a critical role in optimizing oil recovery and oil production strategies, improving oil recovery efficiency, and predicting reservoir behavior. Understanding the complicated kinetics of multicomponent mass transfer at the pore scale after gas injection into petroleum reservoirs is of great importance for estimating GOR and enhanced oil recovery (EOR). However, to date, there is a significant gap in the fundamental process understanding of the complex mass transfer process at reservoir conditions. Using micro-CT technology, we investigate the time dependence of CO2 mass transfer and cluster growth after high pressure CO2 injection into sedimented porous media (sintered 0.2 mm glass beads).Surprisingly, the CO2 partitioning equilibrium is already reached after 2 h. To the best of our knowledge, such a fast CO2 transport through water-saturated porous media, which cannot be explained by linear diffusion models (time scale 100 days for a diffusion length of 10 cm), has not been reported in the literature before. We proposed a conceptual model that assumes CO2 inflation of interfering gas clusters drives cascading CO2 transport. We verified this conceptual model through a time series of experiments at different initial gas saturation, analyzing in each case the spatial cluster distribution, cluster size distribution, and pore occupancy frequency.Whether CO2 inflation of the gas clusters occurs depends on the critical initial gas saturation, which is about 10%. Our main conclusion is that CO2 migration should be considered as gas phase diffusion cascading along a quasi-percolating cluster, since CO2 inflation leads to a high gas saturation of about 26%, which is close to the percolation threshold. Our experimental results support this physical hypothesis. We show for the first time that CO2 clusters can expand over large pore spaces and thus are close to the critical percolation threshold (mobility threshold). The cluster size distribution can be described by a power distribution with the critical exponent 2.19, i.e., it shows universal scaling.We model the interfering mass transfer processes of neighboring gas clusters with a multi-sphere model. Exploring different scenarios for the dissolution kinetics of an ensemble of interfering gas clusters allow a deeper understanding of the complicated mass transfer kinetics and agree well with experimental cluster analyses at specific times.

Heterogeneous Carbonylation of Alcohols on Charge‐Density‐Distinct Mo−Ni Dual Sites Localized at Edge Sulfur Vacancies

AbstractAlcohols carbonylation is of great importance in industry but remains a challenge to abandon the usage of the halide additives and noble metals. Here we report the realization of direct alcohols heterogeneous carbonylation to carbonyl‐containing chemicals, especially in methanol carbonylation, with a remarkable space‐time‐yield (STY) of 4.74 molacetyl/kgcat./h and a durable stability as long as 100 h on Ni@MoS2 catalyst. Mechanistic analysis reveals that the Mo−Ni dual sites localized at edge sulfur vacancies of Ni@MoS2 exhibit distinct charge density, which strongly activate CH3OH to break its C−O bond and non‐dissociatively activate CO. Density functional theory calculations further suggest that the low charge density in Mo−Ni, the Ni site, could significantly lower the barrier for CO migration and nucleophilic attack of methoxy species, and finally leads to the rapid formation of acetyl products. Ni@MoS2 catalyst could also effectively realize the carbonylation of ethanol, n‐propanol and n‐butanol to their acyl products, which may demonstrate its universal application for alcohols carbonylation.

New insights into sustainable in-situ fixation of heavy metals in disturbed seafloor sediments

To address the issues of plume formation and heavy metal ion release during deep-sea mining operations, this study employed multi-sourced mineral composite roasting materials (MMCCM) of varying sizes. An in-situ capping technique was applied within a simulated system to immobilize heavy metals in contaminated sediments. The results demonstrated that capping with MMCCM of different sizes significantly suppressed the upward migration of Cu, Co, and Ni from sediments into the overlying seawater following disturbance. Ion diffusion was identified as a key mechanism driving heavy metal migration. By calculating the release rates of heavy metals during both the disturbed and undisturbed phases, it was found that the application of MMCCM induced a negative diffusion of heavy metals, indicating that the MMCCM-sediment layer functioned as a "sink" for heavy metals. FTIR and XPS analysis showed that the primary mechanisms for heavy metal removal by MMCCM were electrostatic attraction and complexation-precipitation. Additionally, capping with MMCCM facilitated the transition of heavy metals from labile to stable forms within the sediments. Through comprehensive evaluation, the long-term effectiveness of the fixed effects was demonstrated as follows: large MMCCM (L@MCM) > medium MMCCM (M@MCM) > small MMCCM (S@MCM) > powder MMCCM (P @ MCM). Finally, we proposed future research directions and introduced the DQSE framework for the sustainable application of MMCCM. Based on the above findings, this study provides new insights and research references for the in-situ immobilization of heavy metals and plume reduction during future deep-sea mining processes.

Genesis of an Inorganic CO2 Gas Reservoir in the Dehui–Wangfu Fault Depression, Songliao Basin, China

This study systematically examines the origins and formation mechanisms of inorganic CO2 gas reservoirs located within the Dehui–Wangfu Fault in the southeastern uplift region of the Songliao Basin. The research aims to clarify the primary sources of inorganic CO2, along with its migration and accumulation processes. The identification of the Wanjinta gas reservoir within the Dehui–Wangfu Fault Zone, abundant in inorganic CO2, has sparked significant interest in the pivotal roles of volcanism and tectonic activity in gas generation and concentration. To analyze the release characteristics of CO2, this study conducted degassing experiments on volcanic and volcaniclastic rock samples from various boreholes within the fault trap. It evaluated CO2 release behaviors and controlling factors across varying temperatures (150 °C to 600 °C) and particle sizes (20, 40, and 100 µm). The findings indicated a negative correlation between CO2 release and particle size, with a notable transition at 300 °C—marking this temperature as critical for the release of adsorbed and lattice gases. Moreover, volcaniclastic rocks exhibited higher CO2 release compared to volcanic rocks, attributable to their larger specific surface area and higher porosity. At 600 °C, the decomposition of the rock crystal structure results in substantial gas escape. These observations suggest that the inorganic CO2 in this area derives not only from mantle sources but is also influenced by crustal components. Elevated temperatures prompted by tectonic activity and magmatic intrusion facilitated the degassing of the surrounding rocks, allowing released CO2 to migrate upwards through the fracture system and accumulate in the shallow crust, ultimately forming a gas reservoir. This study enhances the understanding of volcanic rock’s roles in inorganic CO2 gas generation and migration, highlighting the fracture system’s critical controlling influence on gas transport and aggregation. The findings indicate that inorganic CO2 gas reservoirs in the Dehui–Wangfu Fault Zone primarily originate from mantle sources with a mixture of crustal gases. This discovery offers new theoretical insights and practical guidance for the exploration and development of gas reservoirs in the Songliao Basin and similar regions.

Revealing crucial factors governing magnetic properties of high-energy ball-milled CoFe2O4 nanoparticles

Nanostructured spinel-type ferrites have attracted significant interest from both the aspects of fundamental research and industrial application owing to their outstanding electronic and magnetic properties. Understanding the factors governing their magnetic properties is important for designing advanced materials with tailored features. In this work, we have conducted a systematic investigation on the structural, electronic, and magnetic properties of high-energy ball-milled CoFe2O4 nanoparticles, which possess a cubic spinel structure and average crystallite sizes (D) ranging from 334 nm for the initial bulk material to 11.7 nm after 120 min of milling. Our observations indicated that the high-energy milling leads to the migration of Co2+ ions from the octahedral B site to the tetrahedral A site, and vice versa for Fe3+ ions. The concentration of Co2+ ions at the A site increases linearly versus the 1/D value. Unlike previous studies on CFO, we have found that the spin canting of Fe3+ ions occurred at both the A and B sites within the inner core, not only on the surface of nanoparticles. The spin canting angles φA and φB increase with grain-size reduction. Although the milling-induced changes in the cation distribution and spin canting are expected to significantly increase the saturation magnetization, this effect is overshadowed by the decrease caused by surface spin disorder. In other words, the surface effects play the primary role affecting the magnetic properties of the milled CFO nanoparticles.

A New Methodology for Quantitative Risk Assessment of CO2 Leakage in CCS Projects

Summary Assessing risks during carbon dioxide (CO2) sequestration involves a systematic process to identify them (risk assessment), analyze, prioritize, score them (risk analysis), develop mitigation strategies, and plan for measurement, monitoring, and verification (MMV) activities. In this context, risk assessment and analysis are often conducted involving qualitative approaches and/or subjective evaluations based on experts judgments. In this paper, we propose to use numerical results of dynamic subsurface modeling to assess risks in a more precise, less subjective, and quantitative manner, enabling a comprehensive definition of effective MMV plans. In this context, MMV evolves into modeling, measurements, monitoring, and verification [(M)MMV]. The conceptual model used for this study integrates flow and geomechanical-coupled behavior to assess caprock integrity, faults reactivation, and ultimately the risk of CO2 leakage. Uncertainty analysis and a 4D probabilistic workflow are used to quantify the likelihood and consequences of CO2 leakage and to score risks. The proposed approach offers a general framework to enable subsurface-modeling-based quantitative risk assessment (QRA) for the definition of successful (M)MMV plans. In this study, we have focused on the QRA of leakage risks through the fault and intact caprock. Other applications are possible, such as: (1) leakage risks through the caprock resulting from caprock failure; (2) lateral CO2 migration leading to permit limits violation or inducing interferences with neighboring activities; (3) leakage risks resulting from loss of well integrity; (4) risks of faults reactivation; (5) risks of surface heave; and (6) risks of induced seismicity. All these results can be used to formulate effective (M)MMV strategies for an optimized and cost-effective risk mitigation.

Risk assessment and management strategy of geologic carbon storage in multi-well site

Many oil and gas production areas may serve as potential geologic carbon storage(GCS) sites, but large-scale CO2 injection in these sites with multiple legacy wells poses a leakage risk. Therefore, it is crucial to analyze the well leakage risk of these GCS sites and develop effective risk management strategies to minimize CO2 and brine leakage. In this study, we hypothesized a GCS site based on the Jingbian area in the Ordos Basin, which has 177 legacy wells. We conducted a three-dimensional geological modeling of the site and simulated the injection and migration of CO2. Using the National Risk Assessment Partnership’s open-source Integrated Assessment toolkit, we outlined a workflow for assessing the risk of CO2 and brine leakage in multi-well site. Simulations of CO2 and brine leakage through 177 existing wells into the USDW or the atmosphere are used as an indicator of potential risk. Finally, we proposed risk management strategies based on well integrity, injection rate, and pollution range, verifying their effectiveness. The results of the 95th percentile (P95) model implementation showed that the leakage risk of GCS sites was low over 150 years, with a CO2 leakage of 15,996.4 tonnes(0.16 % of the 107 t injected). The risk-based strategy outperformed both distance-based strategy and hybrid strategy overall. Reducing injection rates alone proved ineffective as a risk management strategy. Only high-risk wells near the injection zone may cause pollution to USDW. Meanwhile, legacy wells have negligible impact on atmospheric pollution. The management strategy based on pollution range can be used as a supplement to the risk-based strategy in practical engineering.

The Why, What, Who, When, and Where of Carbon Capture and Storage in Southern Ontario

This paper reviews the five Ws (Why, What, Who, When, and Where) of carbon capture and storage in southwestern Ontario. This area is home to nearly one quarter of Canada’s population and approximately three-quarters of one million people work in the manufacturing sector. Fifteen of the province’s top 20 CO2 emission point sources are in this area. The industries responsible for these emissions include steel mills, refineries and petrochemical plants, and cement plants. These industries are part of the hard-to-abate sector, in that CO2 is used or generated as an integral part of the industrial process. As such, eliminating or even reducing emissions from these industries is a difficult task. Carbon capture and storage (CCS) projects aim to sequester that gas in sedimentary basins over periods exceeding several thousand years. To this end, deeply buried (> 800 m) porous and permeable rocks (a repository) must be overlain by impermeable rocks that act as a seal, preventing the upward migration of CO2 into the atmosphere. The possibility that injection activities could trigger seismicity is but one of the additional considerations. When operational, CCS projects have a negative carbon footprint and the desirability of developing and using this technology has been established for over 20 years. True CCS projects differ from carbon capture, utilization, and storage (CCUS) projects in that the former are only designed with sequestration in mind. One type of CCUS project involves using CO2 for enhanced oil recovery (EOR) and this technology has been employed for several decades. Cambrian sandstones are the most suitable injection targets for CCS in southwestern Ontario because previous oil and gas drilling has shown the rocks to have the necessary characteristics. They are buried below 800 m, can be tens of metres thick, and have adequate porosity and permeability. However, the Cambrian section is lithologically and stratigraphically heterogeneous and oil, gas, and brine can all be present in the pore space. The extent to which this complexity will affect CO2 injection has not yet been evaluated.

A Leakage Safety Discrimination Model and Method for Saline Aquifer CCS Based on Pressure Dynamics

The saline aquifer CCS is a crucial site for carbon storage. Safety monitoring is a key technology for saline aquifer CCS. Current CO2 leakage detection methods include microseismic, electromagnetic, and well-logging techniques. However, these methods face challenges, such as difficulties in determining CO2 migration fronts and predicting potential leakage events; as a result, the formulation of test timing and methods for these safety monitoring techniques are somewhat arbitrary. This study establishes a gas–water two-phase seepage model and solves it using a semi-analytical method to obtain the injection pressure and the derivative curve characteristics of the injection well. The pressure derivative curve can reflect the physical properties of the reservoir through which CO2 flows underground, and it can also be used to determine whether CO2 leakage has occurred, as well as the timing and amount of leakage, based on boundary responses. This study conducted sensitivity analyses on eight parameters to determine the impact of each parameter on the bottom-hole pressure and its derivatives, thereby obtaining the influence of its parameters on different flow stages. The research indicates that, when a steady-state flow characteristic appears at the outer boundary, CO2 leakage will occur. Additionally, the leakage location can be determined by calculating the distance from the injection well. This can guide the placement and measurement of safety monitoring methods for saline aquifer CCS. The method proposed in this paper can effectively monitor the timing, location, and amount of leakage, providing a technical safeguard for promoting CCS technology.

The effects of formation inclination on the operational performance of compressed carbon dioxide energy storage in aquifers

Compressed CO2 energy storage in aquifers (CAESA) is a net-zero energy storage technology. Due to the widespread existence of inclined aquifers in nature, it is of practical significance to study the influence of inclined reservoirs on CO2 migration, safety and energy efficiency of the storage system. We build 3D numerical models with different dips (0°–16°), analyze the hydrodynamic and thermodynamic behavior of the system, and discuss the effects of injection schemes (temperature and pressure) on wellbore pressure, temperature, and energy efficiency. The results show that formation dip affects the energy storage characteristics of the system mainly by affecting the migration and distribution of CO2 in the aquifer. The greater the formation dip, the greater the difference in CO2 distribution, and the farther the CO2 diffuses upward along the dip direction. The farthest migration distances in the low- and high-pressure aquifers, occurring in the case of 16° formation dip, increase by 100 and 53 m, respectively, compared with those of the flat formation. The average daily energy storage efficiency decreases with the increase in formation dip angle. The dip angle of aquifer which is selected for compressed CO2 energy storage should not exceed 8°.