CO2 Leakage Research Articles

Formation and decomposition characteristics of CO2+TBAB hydrate for a safer CO2 storage

CO2 hydrate caps can effectively reduce the leakage risk from subsea CO2 sequestration. TBAB (tetrabutylammonium bromide) affects temperature and pressure required for the CO2 hydrate formation, which improves hydrate cap application. This study analyzes hydrate formation and decomposition characteristics in TBAB + CO2 system under different initial pressures and TBAB concentrations. The results show that the addition of TBAB effectively expand CO2 hydrate stable area and prevent CO2 leakage. 5 wt% TBAB not only provides crystal nucleus for hydrate formation and shortens the induction period, but also increases CO2 hydrate cap temperature to 290.3 K. The hydrate decomposition process in TBAB system is divided into CO2 ·nCO2 and TBAB·26H2O·nCO2 decomposition stage. Comparing with hydrate decomposition process in pure water system, it is found that TBAB mainly affects the second stage of hydrate decomposition process. In 5 wt% TBAB system, the hydrate decomposition process was affected by TBAB after more than 68 % hydrate decomposition. It is found that the hydrate decomposition rate with TBAB is almost 1/7 of that without TBAB. This study provides experimental support for expanding the application of CO2 hydrate caps, and provides a basis for determining the geological storage area of CO2 in sediments.

A pore-scale study of fracture sealing through enzymatically-induced carbonate precipitation (EICP) method demonstrates its potential for CO2 storage management

Geological fractures are mechanical breaks in subsurface rock volumes that provide important subsurface flow pathways. However, the presence of fractures can cause unwanted challenges, such as gas leakage through fractured caprocks, which must be addressed. In this study, the dynamics of enzymatically induced carbonate precipitation in rock fractures and their subsequent influence on CO2 leakage were investigated from a pore-scale perspective for the first time. This was achieved through real-time monitoring of the injection of the solution into a rock-microfluidic flow cell using optical and scanning electron microscopy. It was revealed that the main growth dynamics occur during the first three injection cycles, with growth continuing until the fracture aperture is fully closed in the 6th cycle. Based on the flow simulation, a significant reduction of up to 25% in the CO2 conductivity of the original fracture is expected even after the first treatment cycle. Future studies are suggested to explore different resolutions, testing conditions, and to conduct 3-dimensional investigations of the growth dynamics.

SeisRAFT: A recurrent deep learning network for 4D seismic registration and CO2 storage monitoring

The alignment or registration of seismic images is an important and extensively researched aspect in seismic data processing. This process plays a pivotal role in evaluating the evolution of CO2 plumes and assessing the potential for CO2 leakage from its reservoir storage when using 4D or time-lapse seismic methodology. The computer vision community has demonstrated considerable advantages in employing deep learning for such tasks, particularly when confronted with substantial shifts, mismatches, and noises in complex images. In this study, we leverage a cutting-edge recurrent deep learning network known as recurrent all-pairs field transforms (RAFT), incorporating tailored modifications to address seismic matching challenges. We evaluate the network's performance on both synthetic and field 4D CO2 seismic data sets, showcasing its superior accuracy and effectiveness compared to a widely used traditional method. Particularly, in some intricate and ambiguous instances, where even human vision may struggle to identify corresponding events between images, our deep learning method exhibits strong and reliable performance. Validated results confirm that this lightweight multiscale network, trained through self-supervised learning, offers a rapid, parameter-free, and end-to-end solution for 4D image matching in subsurface CO2 storage monitoring with potential applicability to many other seismic registration tasks.

Evaluating a Computerized CCS Model Against Current Technologies to Optimize Environmental Conservation for the Patuakhali Power Plant in Bangladesh.

The burgeoning focus on power generation in Bangladesh has spurred the government to embark on ambitious plans for the installation of power plants. Among these developments is the impending operation of a 2*660MW coal-power station in Patuakhali which will operates end of the month in December 2024. There is concern about this plant's carbon-dioxide emission and mitigation in the atmosphere surrounding this area, which may cause a variety of health problems as well as threaten the biodiversity of the plant zone. The proposed technology will not cover all situations and may present some challenges when compared to other technologies. Utilizing an established operational model sanctioned within the country, our assessment revealed an approximate daily carbon emission of 4.806 million kilograms from the power plant. Employing the Sundarbans' sequestration rate, we calculated a carbon tolerance level of around 4.2 million kilograms per day for the plant area. Despite the emission levels being considered marginal, given the Sundarbans' capacity for carbon sequestration, our study highlights the potential of computerized Carbon Capture and Storage (CCS) technology to significantly mitigate emissions, potentially reducing them to near-zero levels. This research also compares a computerized CCS model with exiting model which can optimize environmental conservation by simulating and analyzing the effectiveness of different carbon capture technologies, selecting optimal storage sites, and assessing the lifecycle impact of CCS projects. Among the most notable solutions is carbon capture and storage (CCS) technology, which can cut carbon emissions by over 90%. Furthermore, the incorporation of a computerized system can reduce emissions by over 90% as well as stop CO2 leaks and lessen related risks. It enhances operational efficiency, reduces costs, and supports policy compliance through precise data-driven insights. However, the security of the entire carbon capture, transportation, and storage process is guaranteed by this all-encompassing strategy. Recognizing the Sundarbans' critical role in sustaining a diversity of life and nature, it is crucial to strike a balance between environmental preservation and economic development. If the system is fully integrated and functional, advanced technologies like computerized carbon capture and storage have the potential to minimize carbon emissions to zero. It also offers economic benefits as well as carbon credits, and improves air quality and ocean health by mitigating pollutants and CO2 emissions.

Physicochemical behavior and impact of CO2 and CH4 plumes during gas-rich water leakage in a shallow carbonate freshwater aquifer

Carbon capture and storage (CCS) is a promising technology for reducing CO2 emissions. Significant concerns have emerged about the potential leakage of CO2 into shallow aquifers, highlighting the risk to water quality and environmental safety. This underscores the importance of finding monitoring tools suitable for different geological scenarios. If leakage occurs in the context of depleted reservoirs being used for CO2 storage, residual CH4 from the storage complex will likely be entrained together with CO2. However, few studies have addressed the implications of CH4 presence and its potential as a monitoring parameter during CO2 leakage.To address this gap, we simulated a leakage event by injecting water enriched with CO2 and CH4 into a shallow limestone aquifer. The impact of the injection was monitored using a combination of laboratory measurements on water samples and in-situ sensors located downstream from the injection well.All parameters were affected by the simulated leakage. Some monitoring tools allowed us to differentiate the leakage event from natural variations. A key finding of this study was that at 7 m from the injection well, the CH4 breakthrough occurred roughly one day before the CO2 breakthrough, highlighting the potential of CH4 as an early indicator of CO2 leakage and suggesting interesting prospectives for industrial-scale sites. However, further research is needed to confirm the potential of CH4 as a CO2 leakage indicator at industrial scales, due to potential methane oxidation and loss of the signal with longer times and distances.This study contributes to a better understanding of the potential risks and effective monitoring strategies associated with CO2-CH4 leakage in carbonate aquifers.

Potential applicability of calcium phosphate modified portland cement paste for geologic sequestration of CO2

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical CO2, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of CO2 is exceptionally high, Ca2+ concentration in portland cement concrete drops significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this work, it is hypothesized that if fairly large quantity of the hydration product becomes more thermodynamically stable than calcite, the damage caused by rapid carbonation will certainly be minimized. For this purpose, portland cement system was modified by monocalcium, dicalcium and tricalcium phosphates to produce hydroxyapatite in portland cement paste. According to the experimental results, addition of calcium phosphate produced hydroxyapatite. Among three different calcium phosphates, monocalcium phosphate showed the most significant impact on hydration. It caused faster stiffening and delayed calcium silicate hydration. Although cement pastes modified by calcium phosphates showed less compressive strength than plain cement paste, they showed an excellent durability after exposure to supercritical CO2. It is clear from the results that the potential applicability of calcium phosphate modification in portland cement for geologic sequestration of CO2 was successfully proven.

Recent Advances in Geochemical and Mineralogical Studies on CO2–Brine–Rock Interaction for CO2 Sequestration: Laboratory and Simulation Studies

The urgent need to find mitigating pathways for limiting world CO2 emissions to net zero by 2050 has led to intense research on CO2 sequestration in deep saline reservoirs. This paper reviews key advancements in lab- and simulation-scale research on petrophysical, geochemical, and mineralogical changes during CO2–brine–rock interactions performed in the last 25 years. It delves into CO2 MPD (mineralization, precipitation, and dissolution) and explores alterations in petrophysical properties during core flooding and in static batch reactors. These properties include changes in wettability, CO2 and brine interfacial tension, diffusion, dispersion, CO2 storage capacity, and CO2 leakage in caprock and sedimentary rocks under reservoir conditions. The injection of supercritical CO2 into deep saline aquifers can lead to unforeseen geochemical and mineralogical changes, possibly jeopardizing the CCS (carbon capture and storage) process. There is a general lack of understanding of the reservoir’s interaction with the CO2 phase at the pore/grain scale. This research addresses the gap in predicting the long-term changes of the CO2–brine–rock interaction using various geochemical reactive transport simulators. Péclet and Damköhler numbers can contribute to a better understanding of geochemical interactions and reactive transport processes. Additionally, the dielectric constant requires further investigation, particularly for pre- and post-CO2–brine–rock interactions. For comprehensive modeling of CO2 storage over various timescales, the geochemical modeling software called the Geochemist’s Workbench was found to outperform others. Wettability alteration is another crucial aspect affecting CO2–brine–rock interactions under varying temperature, pressure, and salinity conditions, which is essential for ensuring long-term CO2 storage security and monitoring. Moreover, dual-energy CT scanning can provide deeper insights into geochemical interactions and their complexities.

A new salt-precipitation-based self-remediation model for CO2 leakage along fault during geological CO2 storage

Salt precipitation occurring in fault zone, due to CO2-brine co-leakage, would create an opportunity to prevent CO2 leakage along fault, i.e., salt-precipitation-based self-remediation model. To investigate the new model, the physical model on salt precipitation was proposed, considering co-leakage of CO2 and brine along fault. Theoretical model was given on salt precipitation, and the numerical model was established to validate the salt precipitation occurring in fault zone. The numerical results indicated that salt precipitation indeed occurred in fault zone, and CO2 leakage rate was obviously decreased after salt precipitation. Importantly, evolution of salt precipitation in fault was concluded, from viewpoint of co-leakage of CO2 and brine along fault, and degree of salt precipitation was characterized, using representative parameters such as the starting time, ending time, lasting time of salt precipitation, and solid saturation. Especially, the self-remediation model for CO2 leakage based on salt precipitation was confirmed feasibly. The self-remediation capacity was closely related to degree of salt precipitation (or lasting time of salt precipitation), and was directly evaluated by the decreasing in CO2 leakage rate before and after salt precipitation. Finally, the parametric analyses showed that: (1) the potential correlation was found among the lasting time of salt precipitation, solid saturation and self-remediation capacity; (2) the higher CO2 injection rate and fault permeability, the smaller fault width and permeability of lower saline aquifer were helpful for salt precipitation and self-remediation capacity; (3) no salt precipitation occurred for the smaller CO2 injection rate and fault permeability, the larger fault width and permeability of lower saline aquifer.

Geomechanical risk assessment for CO2 storage in deep saline aquifers

We study CO2 injection into a saline aquifer intersected by a tectonic fault using a coupled modeling approach to evaluate potential geomechanical risks. The simulation approach integrates the reservoir and mechanical simulators through a data transfer algorithm. MUFITS simulates non-isothermal multiphase flow in the reservoir, while FLAC3D calculates its mechanical equilibrium state. We accurately describe the tectonic fault, which consists of damage and core zones, and derive novel analytical closure relations governing the permeability alteration in the fault zone. We estimate the permeability of the activated fracture network in the damage zone and calculate the permeability of the main crack in the fault core, which opens on asperities due to slip. The coupled model is applied to simulate CO2 injection into synthetic and realistic reservoirs. In the synthetic reservoir model, we examine the impact of formation depth and initial tectonic stresses on geomechanical risks. Pronounced tectonic stresses lead to inelastic deformations in the fault zone. Regardless of the magnitude of tectonic stress, slip along the fault plane occurs, and the main crack in the fault core opens on asperities, causing CO2 leakage out of the storage aquifer. In the realistic reservoir model, we demonstrate that sufficiently high bottomhole pressure induces plastic deformations in the near-wellbore zone, interpreted as rock fracturing, without slippage along the fault plane. We perform a sensitivity analysis of the coupled model, varying the mechanical and flow properties of the storage layers and fault zone to assess fault stability and associated geomechanical risks.

Diffusive Leakage of scCO2 in Shaly Caprocks: Effect of Geochemical Reactivity and Anisotropy

Summary Supercritical carbon dioxide (scCO2) trapping mechanisms within carbon geostorage (CGS) primarily hinge on the upper caprock system, with shales being favored for their fine-grained nature and geological abundance. Experimental assessments of CO2 reactivity in brine-saturated shales reveal microstructural changes, raising concerns about long-term CO2 leakage risks. Existing models of scCO2 transport through caprocks lack consideration for shale anisotropy. This study addresses these gaps by investigating the diffusive properties and propagation of geochemical reactivity in shaly caprocks, accounting for anisotropy. Horizontal and vertical core samples from three shale formations with varying petrophysical characteristics underwent mineralogical, total organic carbon (TOC), porosity, and velocity measurements. scCO2 treatment for up to 3 weeks at 150°F and 3,000 psi was conducted. The propagation of geochemical reactivity was monitored by multiple surface X-ray fluorescence (XRF) measurements and fine polishing. A nuclear magnetic resonance (NMR)-based H2O-D2O fluid exchange protocol was used to quantify effective diffusivities and tortuosities parallel and perpendicular to bedding. Results indicate preferential surface reactivity toward carbonate minerals; however, the apparent reaction diffusivity of the shaly caprock is notably slow (~10−15 m2/s). This aligns with previous experimental and reactive transport modeling studies, emphasizing long timescales for carbonate dissolution reactions to influence shale caprock properties. Shale-effective diffusivities display anisotropy increasing with clay content, where diffusivities parallel to bedding exceed those perpendicular by at least three times. Faster horizontal diffusion in shaly confining zones should be considered when estimating diffusive leakage along faults penetrating these zones, a significant risk in CGS. Post-scCO2 treatment, diffusivity changes vary among samples, increasing within the same order of magnitude in the clay-rich sample. Nonsteady-state modeling of scCO2 diffusion suggests limited caprock penetration over 100 years, with a minimal increase from 5 m to 7 m post-scCO2 treatment for the clay-rich sample. This study extends existing literature observations on the slow molecular diffusion of scCO2 within shaly caprocks, integrating the roles of geochemical reactions and shale anisotropy under the examined conditions.

Anomaly detection for geological carbon sequestration monitoring

Geological carbon sequestration (GCS) is a method to reduce the emissions of CO2 into the atmosphere. During GCS operations CO2 is captured from the atmosphere or industrial activities and stored in geological formations for permanent storage. Monitoring is an important element of GCS because it ensures that the stored CO2 remains safely contained in the intended formation during the long term. Additionally, monitoring wells can help to detect CO2 leaks, prompt remediation actions, and provide valuable information to optimize storage by monitoring the behavior of the CO2 over time. In this work, we propose a method for GCS anomaly detection based on an LSTM Autoencoder Neural Network and Isolation Forest. The LSTM-Autoencoder uses the monitor Bottomhole Pressure (BHP) response while CO2 is being injected into a geological structure. To account for the subsurface uncertainty, multiple subsurface model realizations are created, and using reservoir simulation, the multiple monitor BHP are generated to capture the subsurface uncertainty. Anomaly BHP points are detected using the residuals of the LSTM-Autoencoder and Isolation Forest. Additionally, an anomaly score based on the subsurface uncertainty is proposed. Finally, the method robustness is evaluated using point outliers, level shift outliers, and transient shift outliers as anomaly BHP signals. Early detection of abnormal BHP pressure signals can indicate the presence of subsurface fractures, faults, or leaks. Consequently, the correct detection of anomaly points in the pressure signals is of great importance.

Measurement of CO2 leakage from pipelines under CCS conditions through acoustic emission detection and data driven modeling

CO2 leakage from carbon capture and storage (CCS) networks may lead to ecological hazards, bodily injury and economic losses. In addition, captured CO2 often contains impurities which affect the leakage behavior of CO2. This paper presents a method for continuous and quantitative measurements of CO2 leakage flowrate and the volume fraction of impurities by combining data-driven models with acoustic emission (AE) and temperature sensors. Three data-driven models based on artificial neural network (ANN), random forest (RF), and least squares support vector machine (LS-SVM) algorithms are established. The outputs from the three data-driven models are then integrated to give improved results. Experimental work was conducted on a purpose-built CO2 leakage test rig under a range of conditions. N2 was injected to the CO2 gas stream as an impurity medium. Results show that the integrated model yields a relative error within ±4.0 % for leakage flowrate and ±3.4 % for volume fraction of N2.

Enhancement of CO2 monitoring in the sleipner field (north sea) using seismic inversion based on simulated annealing of time-lapse seismic data

The primary aim of this research is to enhance seismic data interpretation and CO2 monitoring by utilizing seismic inversion techniques based on the simulated annealing method. Simulated annealing is a global optimization technique employed for inverting seismic data and provides better results as compared with local optimization-based inversion. This methodology is implemented in the Utsira Formation, located at a depth of 1000 m within the Sleipner Field, Norway. The study encompasses the analysis of three sets of time-lapse seismic data, first from 1994 (pre-injection), followed by surveys in 1999 and 2001, corresponding to the injection of 2.35 million tonnes and 4.26 million tonnes of CO2, respectively. Firstly, synthetic data is used to check the reliability of the algorithm followed by real data application. This process starts by performing the inversion analysis on the synthetic data which shows a decrease in the impedance values observed at the injection site whereas the seismic amplitude increases. The qualitative as well as quantitative analysis depicts that the algorithm works satisfactorily. The same process is applied to the real data from the Sleipner field. Acoustic impedances are calculated using a simulated annealing-based inversion scheme for the pre-injection case in 1994 and post-injection scenarios in 1999 and 2001. Because of the presence of injected CO2 in the years 1999 and 2001, a low impedance zone that ranged from 2000 m/s*g/cc to 2400 m/s*g/cc appeared at the time interval of 0.85–1.10sec. The interpretation of the inverted impedance section and seismic attribute analysis show no signature of CO2 leakage. The results indicated that the inverted section which is derived from the SA optimization technique shows very clear CO2 information offering a more realistic representation with enhanced resolution of the CO2 plume and its migratory paths.

Effect of mineral dissolution on fault slip behavior during geological carbon storage

Geological carbon dioxide storage is one of the most effective technologies to reduce greenhouse gas emissions to the atmosphere. The mineral dissolution is inevitable during the long-term storage process, while the chemical effect on fault slip behavior remains poorly understood. In this paper, we present a hydro-chemical–mechanical coupled fault reactivation study using the unified pipe-interface element method (UP-IEM). The impact of chemical dissolution on stress redistribution is considered. The accuracy of the numerical method to simulate reactive solute transport and fault frictional slip are confirmed by analytical solution and numerical verification. Two different fault tectonic scenarios, of which fault locating in the caprock and fault crosscutting the reservoir and caprock, are designed to investigate the fault slip behavior induced by mineral dissolution. The effect of dissolved CO2 solute concentration, fault aperture, reservoir permeability and chemical reaction rate are discussed. Results show that fault locating in the caprock is easier to be activated. The chemical reaction has a more significant effect on fault slip behavior than fluid pressure during the long-term low-velocity CO2 leakage. The increase of CO2 solute concentration and reservoir reaction rate cause an obvious growth on fault slip displacement. The decrease of fault initial aperture results in the fault slip velocity slower and the slipping area smaller. The high-permeability reservoir keeps the fault more stable than low-permeability reservoir under the influence of mineral dissolution.

Investigation of Pipeline CO2 Leakage and Diffusion on Offshore Platforms Based on Numerical Simulation.

Pipeline transportation of CO2 is the key link to realize carbon capture, utilization, and storage. CO2 pipeline transportation may face the risk of leakage, which poses a great threat to the production process and personnel safety. It is of great significance to study the leakage and diffusion characteristics of CO2 in pipeline transportation for the safety design and personnel protection of the offshore CO2 storage platform. In order to study the leakage and diffusion characteristics of CO2 in pipeline transportation on offshore platforms, a physical model of a target platform and several numerical models were built, and a series of pipeline CO2 leakage and diffusion simulations were carried out using the method of numerical simulation. Based on the simulation results, the temperature distribution and CO2 concentration distribution on the offshore platforms after leakage were measured and analyzed. The influence of leakage direction (horizontal and oblique 45° upward) was also studied. Dangerous areas on the platform and suggestions for staff evacuation were given according to the simulation results. The research results of this work can provide guidance for the safe operation of offshore CO2 storage platforms.

Influence of the CO2–brine–rock interaction on the plastic zone of sandstone

During the long-term CO2 storage process, the CO2–brine–rock interaction (CBRI) may change the elastic-plastic behaviors of sandstone reservoirs, potentially leading to rock damage and CO2 leakage. A good understanding of the influence of the CBRI on the plastic zone of sandstone is crucial for evaluating the rock fracturing processes. In this paper, three-point bending tests were conducted under both monotonic and cyclic loading conditions, and the digital image correlation technique was used to analyze the elastic and plastic characteristics of the samples. The experimental results showed that the CBRI decreases the yield strength and corresponding crack mouth opening displacement by 25 % and 65%, respectively, thus increasing the probability of fracturing. Additionally, it was found that the CBRI enlarges the plastic zone by about 20 %. The size of the theoretical plastic zone in the sandstone sample for different loads was determined, and the ratio of the plastic zone size in the samples with CO2–brine saturation to that without CO2–brine saturation was found to be about 1.18. Finally, the mesoscale factors affecting the plastic zone size after CO2–brine saturation were analyzed. This study helps to understand the effect of the elastic-plastic behavior of sandstone on reservoir stability during long-term CO2 storage.

A study on decompression wave propagation characteristics during CO2 pipeline leakage with consideration of gas‐liquid transition

AbstractPipelines stand as the most cost‐effective method for large‐scale transportation of CO2 from a source point to the storage site, especially over extensive distances. The potential for crack propagation following a pipeline rupture highlights the need for precise analysis of decompression wave propagation. To accurately model this, understanding the decompression wave's propagation laws becomes imperative. Although previous studies have predominantly focused on pipeline leaks within the dense phase or supercritical state, the transition from liquid to gas during leakage significantly affects the decompression wave propagation. When a gaseous CO2 pipeline ruptures, the high Joule‐–Thomson coefficient causes a swift temperature plunge, potentially leading to a gas–liquid transition. However, research on how this phase transition impacts the decompression wave characteristics is limited. To address this gap, this study proposes a transition computational fluid dynamics model to predict the decompression wave behavior. The model is validated with an industrial‐scale full‐bore rupture experiment. The results reveal that the gaseous CO2 leakage induces a pressure plateau at a certain distance from the leakage due to the gas‐liquid phase transition. The influences of initial conditions on this pressure plateau and decompression wave are also explored. This study provides valuable insights into understanding the decompression wave behaviors of gaseous CO2 pipelines, which are essential for ensuring the safety and reliability of CO2 transportation within the carbon capture and storage technology chain. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Future directions in geological research impacting renewable energy and carbon capture: A synthesis of sustainable management techniques

Geological research plays a pivotal role in shaping the future of renewable energy and carbon capture initiatives, offering insights into sustainable management techniques. This review synthesizes the future directions in geological research that impact renewable energy and carbon capture, focusing on sustainable management techniques. Future geological research will increasingly focus on enhancing the integration of renewable energy sources into existing energy systems. This includes the development of innovative geological mapping techniques to identify and characterize renewable energy resources with greater precision, aiding in the selection of optimal sites for energy production. Additionally, there will be a growing emphasis on utilizing geological data to assess the feasibility of carbon capture and storage (CCS) projects, particularly in volcanic regions, where the unique geological characteristics offer potential for efficient carbon sequestration. Another key aspect of future geological research is the advancement of monitoring and modeling techniques to evaluate the long-term performance and environmental impact of renewable energy and CCS projects. This includes the use of advanced geophysical and geochemical methods to monitor subsurface changes associated with energy extraction and carbon storage, ensuring the effectiveness and safety of these practices. Furthermore, future research will explore the potential of geological formations, such as deep saline aquifers and depleted oil and gas reservoirs, for large-scale carbon storage. This will involve developing strategies to enhance storage capacity and mitigate the risk of CO2 leakage, contributing to the sustainable management of carbon emissions. In conclusion, future geological research will play a critical role in advancing renewable energy and carbon capture technologies, offering sustainable management techniques that are essential for addressing climate change. By focusing on innovative mapping, monitoring, and modeling approaches, researchers can pave the way for a more sustainable energy future.

Propagation of CO2 desaturation front in near wellbore region

Understanding the development and propagation of CO2 desaturated front is important for managing the potential of CO2 leakage via injection wells after cessation of CO2 injection. The CO2 desaturation front is the front at which oil becomes fully devoid, referred to as “desaturated”, of CO2. In this research, water injection into an oil reservoir containing CO2 is investigated to understand the effect of CO2 component transfer between brine and oil phases in the near wellbore region, as well as to monitor the development of the CO2 desaturation front. CMG-GEM compositional simulator is used to model the process. A 1D cartesian model, including homogenous properties, is utilised for the modelling. The volume of water needed to be injected to desaturate the oil from the CO2 in the vicinity of the wellbore is determined. Additionally, the velocity of the CO2 desaturation front propagation is calculated, and it is compared with the calculations of the Buckley-Leverett saturation front displacement. The study also examines how different parameters such as salinity, pressure, and temperature affect the velocity of the CO2 desaturation front, as CO2 solubility in water is influenced by these parameters. Results show that while varying the injection water salinity affects the velocity at which the CO2 desaturation front propagates, variation in the initial reservoir temperature and pressure, as well as the formation water salinity, has a minor impact, although they do alter the CO2 solubility and thus the mobilities at the front. The results also indicate that compared to the temperature front, which generally propagates at about one third of the saturation front velocity, the CO2 desaturation front in this specific case study travels at about one tenth of the saturation front velocity, so it takes much longer for the near wellbore region to completely desaturate from CO2. Other sensitivities, such as varying the residual oil saturation, affected the propagation of the CO2 desaturation front. The desaturation front travels at a slower speed at greater residual oil saturations due to the greater mass of immobilised CO2 to be displaced by this mechanism.

Foreign demand shocks and CO2 emission intensity: firm-level evidence from China

ABSTRACT Constrained by data availability and challenges in causality identification, the relationship between trade and the environment remains theoretically ambiguous. This paper constructs a novel Chinese manufacturing firms’ CO2 emission intensity dataset by converting different types of firms’ energy consumption. Using disaggregated transaction data and the Shift-Share design, this paper exploits the effects of foreign demand shocks on firms’ CO2 emission intensity from 2007 to 2014. We document that a 10% increase in foreign demand leads to a 0.28% reduction in firms’ CO2 emission intensity. We find that multi-product exporters can benefit more from foreign demand shocks, and further prove the absence of CO2 leakage due to the EU ETS. This paper demonstrates that firms can be beneficiaries of foreign demand shocks, unmasking the trade-environment nexus by providing micro evidence from the largest developing country.