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Open research questions in CO2 Sequestration and Geologic Interactions

37 unresolved questions extracted from the limitations and future-work sections of 577 CO2 Sequestration and Geologic Interactions papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • However, the microscopic displacement mechanisms of CO2–water two-phase flow under the characteristic high-pressure, low-temperature conditions of the deep sea remain inadequately understood.

    Pore-Scale Imaging of CO2–Water Displacement: Experimental Insights from Microfluidics · 2026 · DOI

  • The diffusive time of flight (DTOF) is insufficient for capturing pressure distribution in high-permeability reservoirs accurately because it fails to properly incorporate the influence of both internal and external boundary conditions.

    Proxy Models Accelerated Using Physics-Based Reduced-Order Model · 2026 · DOI

  • Abstract Mature Niger Delta reservoirs offer a compelling opportunity for integrated CO2-enhanced oil recovery and permanent geological carbon storage, but their heterogeneity, structural complexity, and limited data availability make conventional simulation-based screening workflows difficult to apply at scale.

    Machine Learning–Based Surrogate Modeling and Screening Framework for CO2-Enhanced Oil Recovery and Permanent Carbon Storage in Mature Niger Delta Reservoirs · 2026 · DOI

  • These changes have direct implications for injection control, flow balancing, reservoir integrity, and overall operability, yet remain insufficiently addressed in existing EOR design frameworks.

    Fit-For-Purpose Injection Control Philosophy for CO2–Hydrocarbon Gas EOR in Microporous Carbonate Reservoirs · 2026 · DOI

  • Future research should focus on integrating higher-resolution geological surveys, probabilistic uncertainty quantification, and scenario-based sensitivity testing to further refine deployment planning and ensure safe, cost-effective, and large-scale implementation of CCS in China.

    Deployment-scale CO2 storage capacity and suitability assessment in the Subei Basin, China using a stratified and grid-based framework · 2026 · DOI

  • Although the sensitivity analysis enhances interpretabil- ity, some limitations remain. First, the current framework applies static AHP-derived weights, which may not fully capture spatial variability or site-specific uncertainties. Sensitivity analysis indicates that certain medium-weight indicators, such as reservoir permeability and unit capac- ity, exert disproportionate influence in specific layers, sug- gesting that layer-specific weighting strategies may improve model realism. Second, the analysis is constrained by the availability and spatial resolution of input datasets. Fault and seismic data are commonly mapped at the basin scale and may therefore overlook local-scale heterogeneity. Similarly, lithology and sedimentary facies are represented using formation-scale characteristics due to limited lateral coverage, restricting Fig. 14 Sensitivity analysis of CO2 storage suitability across five stratified reservoir layers 1 3Environmental Earth Sciences (2026) 85:287 explicit quantification of fine-scale facies-controlled capac- ity variations. Recent studies have further highlighted the importance of incorporating geological heterogeneity into regional CCS assessments (Li et al. 2025). In addition to data-related constraints, uncertainty also arises from methodological assumptions. Storage capacity estimates are based on a deterministic volumetric approach that does not explicitly quantify probabilistic uncertainty. Major uncertainty sources include unresolved basin-scale heterogeneity, simplified lithological assumptions within formations, and the use of representative parameter values where data density is limited. Given current data resolution and coverage, probabilistic or Monte Carlo-based analy- ses were not applied to avoid over-interpretation. Instead, uncertainty is addressed through sensitivity analysis, focus- ing on identifying influential indicators rather than defining absolute uncertainty bounds. Recent studies have emphasized interactions between CO₂ storage and underground coal resource development in coal-bearing basins (Lin et al. 2025b). However, economi- cally exploitable coal seams are absent in the Subei Basin, and coal-related constraints therefore do not constitute a con- trolling factor in the present assessment. In addition, long- term storage security and potential environmental impacts associated with leakage pathways remain important consid- erations for CCS deployment (Plampin and Merrill 2025). Future research should incorporate higher-resolution geological surveys, probabilistic weighting methods, and scenario-based perturbation schemes to further refine uncertainty characterization. Emerging approaches inte- grating machine learning with geological modeling may improve prediction efficiency and uncertainty awareness in large-scale CO₂ storage assessments (Lin et al. 2025a). In addition, future deployment-oriented studies may benefit from integrating refined regional storage characterization, dynamic injection strategies, pressure management, and long-term containment behavior into regional assessment frameworks (Gasanzade and Bauer 2025; Dutta et al. 2025). Implications for CCS deployment in China The sensitivity results have direct implications for CO2 storage deployment strategies in China. The dominance of geological stability indicators underscores the neces- sity of rigorous site screening and exclusion of seismically active zones, regardless of depth. The strong sensitivity of source–sink indicators, particularly in shallow layers, highlights the potential for near-source storage hubs to minimize transportation costs and accelerate early deploy- ment. By contrast, deep formations such as DN1 and DN2 Page 15 of 18 287 exhibit relatively stable suitability with respect to reservoir property indicators, suggesting their role as long-term, large-capacity sinks that are less dependent on marginal variations in reservoir quality. Overall, the combination of stratified evaluation and sen- sitivity analysis demonstrates that a differentiated, multi- layered deployment strategy is essential. Rather than a one-size-fits-all approach, shallow layers should prioritize economic proximity and rapid deployment, middle layers require balancing storage capacity with safety, and deep layers should be reserved for large-scale, secure, long-term sequestration (Lin et al. 2025c). These findings provide both methodological and policy-level insights, strengthening the scientific basis for China’s carbon neutrality roadmap.

    Deployment-scale CO2 storage capacity and suitability assessment in the Subei Basin, China using a stratified and grid-based framework · 2026 · DOI

  • 6.1. Principal contributions of the study This study has developed a new Boundary Element formulation for transient CO2 injection in heterogeneous carbonate reservoirs with explicit consideration of reaction-induced porosity and permeability evolution. The proposed model was motivated by the need for computationally efficient yet physically meaningful simulation tools capable of capturing the coupled hydraulic and geochemical processes that govern pressure buildup, injectivity, and storage performance in reactive subsurface systems. By embedding the pressure-diffusion problem in a time-dependent boundary-integral framework and coupling it to constitutive laws for reaction progress, porosity growth, and permeability enhancement, the present work extends classical BEM methodology to a nonlinear class of reservoir problems for which boundary-only formulations remain relatively uncommon. A central contribution of the study lies in the incremental linearization strategy, which preserves the analytical structure of the BEM while allowing hydraulic properties to evolve in time. The method rigorously enforces interface continuity across heterogeneous subregions, treats wells analytically as internal singular sources, and reconstructs transient interior fields without volumetric remeshing. The physical relevance of these methodological advances is demonstrated throughout Section 5 by the consistent interpretation of Figures 1–14 and the quantitative comparisons reported in Tables 2–8. In particular, Table 2 shows that these advances are achieved without sacrificing computational efficiency. 6.2. Main physical findings The numerical results show that reaction-driven permeability evolution substantially alters pressure development during CO2 injection. In homogeneous reactive systems, the near-well dissolution halo shown in Figures 3, 4, and 8 produces moderated long-time pressure buildup and increased injectivity, as confirmed by Figures 9 and 10 and by Tables 5 and 6. Page 39 of 44 F1000Research 2026, 15:903 Last updated: 09 JUN 2026 In heterogeneous reservoirs, the effect is more complex because the initial facies architecture governs early pressure redistribution, while the subsequent reaction redistributes permeability in a spatially nonuniform manner, as illustrated by Figures 11–14 and summarized in Tables 7 and 8. These results demonstrate that the hydraulic response of carbonate storage reservoirs is intrinsically path-dependent and cannot be described adequately using static permeability fields alone. Equally important, the comparison between homogeneous and heterogeneous nonreactive cases, represented by Figures 5–7 and Table 4, shows that geological heterogeneity exerts a strong control on pressure propagation even before reactive alteration becomes active.

    A Transient Boundary Element Framework for Pressure Buildup, Injectivity Enhancement, and Reactive Permeability Evolution During CO₂ Storage in Heterogeneous Carbonate Reservoirs · 2026 · DOI

  • In the context of rapid growth in renewable energy, UHS in depleted shale gas reservoirs has gained attention given its long-duration storage potential and highcapacity characteristics. This work offers an integrative overview of new research on UHS in depleted shale gas reservoirs, covering key topics including biogeochemical reactions, surface and interfacial phenomena, H2 adsorption and diffusion behaviors, and reservoir simulations. Furthermore, the paper addresses the technical, safety, and economic challenges associated with UHS in depleted shale gas reservoirs. The results indicate that H2 injection can trigger redox and non-redox reactions with carbonate, sulfate/sulfide, and clay minerals. Microbes can also metabolize by using H2 as an electron donor. Both abiotic and biotic reactions lead to H2 loss, mineral precipitation and dissolution, and changes in reservoir conditions. Furthermore, the wettability contact angle in typical H2-brine-shale systems is significantly influenced by TOC. Generally, as TOC increases, the contact angle increases, indicating a transition from hydrophilic to H2-wet shale. Therefore, high-TOC shale may be more advantageous for H2 storage, while low-TOC shale might serve better as a caprock. H2 adsorption on shale is usually characterized by monolayer physical adsorption, with adsorption on kerogen exceeding that on inorganic minerals. The presence of CO₂, CH₄, and water competes with H2 for adsorption Wu et al. Carbon Neutral Systems (2025) 1:14 Page 20 of 24 sites, reducing H2 adsorption capacity. H2 diffusion in shale primarily occurs through transitional diffusion and is not significantly affected by kerogen maturity. Additionally, H2 diffuses faster than CO₂ and CH₄, and the diffusion coefficient of H2 increases more notably with temperature. Reservoir simulations show that hydraulic fractures and stimulated areas can serve as H2 storage sites and provide high-permeability pathways for H2 flow. However, fracture closure can significantly impact UHS performance. The recovery ratios of residual natural gas and stored H2 are affected by various factors such as depletion time and well shut-in duration. Using CO₂/CH4 as cushion gases can improve H2 recovery but may also affect H2 purity. Due to the complexity of shale reservoirs, the unique properties of H2 such as high diffusivity and reactivity, and the presence of microbes, efficiently, safely, and economically injecting, storing, and producing H2 in depleted shale gas reservoirs presents significant challenges. To address these challenges, research on UHS in depleted shale gas reservoirs must continue to deepen in multiple areas.

    Underground hydrogen storage in shales · 2026 · DOI

  • Applying this workflow to the UK context reveals the need for advanced assessments of storage candidates such as the Bunter Sandstone Formation, demonstrating that relying solely on basic frameworks is insufficient.

    CO<sub>2</sub> Storage Site Selection: A Comprehensive Review of Current Approaches · 2025 · DOI

  • Given these circumstances, this paper proposes an innovative approach for quantitatively assessing CO 2 leakage risk to address the previous limitations of limited accuracy and insufficient data.

    Quantitative assessment of CO<sub>2</sub> leakage risk in geologic carbon storage management · 2024 · DOI

  • Future research should focus on long‐term field experiments, understanding secondary mineral formation, and refining the application techniques to enhance the overall efficiency and sustainability of ERW.

    CO₂ sequestration and soil improvement in enhanced rock weathering: A review from an experimental perspective · 2024 · DOI

  • The perspectives in experiments, models, and field pilots of CO 2 -ECBM are made, which include but are not limited to the following: conducting a core CH 4 /CO 2 flooding test under in situ conditions, modeling CO 2 -ECBM with real fractures/faults and coal failure, developing a new method for gas migration and leakage monitoring in the field, and enacting relevant standards, laws, and regulations to promote CO 2 -ECBM.

    Recent Advances and Perspectives of CO<sub>2</sub>-Enhanced Coalbed Methane: Experimental, Modeling, and Technological Development · 2023 · DOI

  • Earth’s climate may be stabilized over millennia by solubilization of atmospheric carbon dioxide (CO 2 ) as minerals weather, but the temperature sensitivity of this thermostat is poorly understood.

    How temperature-dependent silicate weathering acts as Earth’s geological thermostat · 2023 · DOI

  • Under the scenario where the leaky wellbore is open to a saline aquifer (thief zone) between the overlying seal (cap rock) and the underground sources of drinking water (USDW), the risk‐based AOR is no larger than the areal extent of the CO 2 plume in the storage reservoir because the pressure buildup in the storage reservoir beyond the CO 2 plume is insufficient to drive formation fluids up a hypothetical leaky wellbore into the USDW.

    Risk‐based area of review estimation in overpressured reservoirs to support injection well storage facility permit requirements for CO<sub>2</sub> storage projects · 2021 · DOI

  • Abstract Methodologies for quantitative risk assessment regarding CO 2 storage operations are currently scarce, mostly because of the lack of experience in this field and the relatively significant degree of uncertainty regarding the subsurface intrinsic properties and the processes occurring after the injection starts.

    Quantitative risk assessment in the early stages of a CO<sub>2</sub> geological storage project: implementation of a practical approach in an uncertain context · 2014 · DOI

  • Results show potential geothermal sedimentary reservoirs suitable for GEE deployment exist in the continental USA; however the characteristics of each site should be investigated through a first stage GEE‐operation to determine GCS capacity.

    Active CO<sub>2</sub> reservoir management for sustainable geothermal energy extraction and reduced leakage · 2013 · DOI

  • Numerical simulations have suggested large‐scale formation, whereas natural occurrences in present‐day or previously CO 2 ‐charged reservoirs are scarce.

    Will dawsonite form during CO<sub>2</sub> storage? · 2013 · DOI

  • Furthermore, no significant changes in pore structure were observed between fresh and exposed samples, suggesting that the extent of dissolution was insufficient to alter the pore network or induce mechanical weakening.

    Is a Depleted Chalk Reservoir Safe for CO2 Storage? · 2026 · DOI

  • Although interest in hydrogen thermophysical properties has increased in the last years, laboratory data specific to porous media conditions relevant for underground storage remain scarce.

    Enhancing Hydrogen Storage Predictions with New Laboratory Data on Transport and Retention in Porous Media · 2026 · DOI

  • Our case study indicates that to complete preparation of a permit application requires (1) improved lithologic characterization information (thicknesses and horizontal and vertical connectivity) and (2) better definition of poorly defined local faults.

    A phased workflow to define permit‐ready locations for large volume CO<sub>2</sub> injection and storage · 2023 · DOI

  • Concomitantly, the dissolution of Ca‐(Al)‐silicate grains takes place but it is limited by the formation of a Si‐rich and Ca‐depleted rim which appears onto the grain surfaces due to an initial hydration step.

    Accelerated carbonation by cement kiln dust in aqueous slurries: chemical and mineralogical investigation · 2017 · DOI

  • Pitzer equations) require the use of binary salt concentrations and are best applicable to polar ionic compounds; but the effect of brines on larger hydrocarbons has not yet been explored.

    Limiting the risk inherent to geological CO<sub>2</sub> storage: The importance of predicting inorganic and organic chemical species behavior under supercritical CO<sub>2</sub> fluid conditions · 2014 · DOI

  • Moreover, there are no data on the rate of nucleation and growth of dawsonite, and numerical predictions are forced into using simplified kinetic expressions with values of kinetic constants obtained from far‐from‐equilibrium dissolution rate experiments, a method that is questioned today.

    Will dawsonite form during CO<sub>2</sub> storage? · 2013 · DOI

  • Environmental risks result mostly from abandoned wells and faults, poorly characterized for carbon storage, and from defective well completions and surface spills during oil and gas production.

    Common attributes of hydraulically fractured oil and gas production and CO<sub>2</sub> geological sequestration · 2012 · DOI

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37 open questions have been extracted from the limitations and future-work passages of 577 CO2 Sequestration and Geologic Interactions papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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