The long-term security of carbon dioxide geological storage (CGS) depends on pore structure evolution driven by CO2-water-rock interactions. Experiments were conducted under simulated reservoir conditions (36 degrees C, 7.2 MPa) using Ordos Basin sandstone as the reservoir rock and C30 cement as the sealing material. Pore and mineral evolution were characterized by nuclear magnetic resonance (NMR) T 2 spectra and x-ray diffraction (XRD). Sandstone exhibited a staged evolution following a dissolution-expansion -> precipitation-contraction -> dynamic equilibrium pattern: an initial expansion phase, where dissolution of reactive minerals (e.g., albite and illite) increased meso- and macropore volume, with porosity reaching a local maximum at approximately 16 h during the early expansion stage, followed by a contraction phase marked by mineral transformation (e.g., anorthite) and particle migration, leading to a dynamic dissolution-transformation balance. In contrast, cement maintained a stable microstructure dominated by micropores. These results indicate that early dissolution may temporarily enhance permeability and leakage risk, whereas subsequent precipitation promotes pore-throat clogging and structural self-sealing, improving long-term integrity. The study demonstrates that pore evolution is controlled by dissolution-precipitation cycles and that NMR T 2 spectra effectively capture these dynamics, providing an experimental basis for evaluating storage capacity and leakage risk in geological CO2 storage.
The reuse of decommissioned offshore platforms for geological carbon storage offers a cost-effective and technically feasible strategy to reduce greenhouse gas emissions in emerging economies. This study presents a comprehensive techno-economic assessment of offshore carbon capture and storage (CCS) hubs in Brazil, with a focus on the Merluza Field in the Santos Basin. A detailed cost model was developed to quantify capital expenditure (CAPEX), operational expenditure (OPEX), and the levelized cost of storage (LCOS) for scenarios involving infrastructure reutilization. Results indicate that site characterization dominates the cost structure, accounting for up to 76% of CAPEX in reuse scenarios, despite an overall 6% reduction in total capital investment when compared with new offshore construction. Annual OPEX is estimated at $7.79 million, and over a 40-year project lifespan, the net present value of operational costs reaches $104.68 million. The LCOS ranges from $12.72 to $35.54 per ton of CO2 for a 1.39 Mtpa case, making the Brazilian scenario economically competitive when compared to international benchmarks such as Sleipner and Quest. Moreover, potential revenues from carbon credits and avoided emission penalties could substantially offset total project costs. These findings highlight the financial viability of offshore CCS in Brazil and reinforce its potential integration into national decarbonization strategies under the Paris Agreement. 2026 Society of Chemical Industry and John Wiley & Sons, Ltd.
Syngas, a vital feedstock in the chemical industry, consists of hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and impurities such as hydrogen sulfide (H2S) and ammonia (NH3). Syngas is used in the production of ammonia, methanol, H2, and so forth. The impurities, such as H2S and CO2, are present in the syngas, which causes a decrease in the quality of syngas, and when H2S and CO2 are released into the air, they cause harm to the environment and contribute to global warming. In the research article, the syngas recovery process was modeled using Aspen Plus software and industrially validated. The Peng-Robson thermodynamic property method is used to simulate the process. The Peng-Robinson is used for hydrocarbons. The effect of the change of the number of distillation stages and the reflux ratio is studied to check the recovery of H2S and CO2 gas. The primary objective is to model and simulate the syngas recovery process. The second objective was to perform a parametric analysis of the process to investigate the effects of changing the number of distillation columns and reflux ratio, as well as studying the impacts of CO2 and H2S recovery and heat integration. In this analysis, the process stream of product steam is utilized to decrease the temperature of the feed stream. It reduced the utility cost of the inlet feed stream, resulting in a 0.03% decrease in cost. The third objective was to conduct a cost analysis of the process before the parametric analysis and the heat integration method to analyze the process's profit. This was due to the process recovering 1.06% H2S gas and 0.002% CO2, and calculating the utilities cost of the process. The fourth objective is an exergy analysis of the process in which the overall exergy destruction is 0.42%. The fifth objective was to use the simulation software ALOHA to model the dispersion of H2 gas. In the case, H2 gas is released into the air; it is a hazardous gas, destroying 1.2 mi. The proposed cryogenic approach achieves 85% CO2 removal, 99% H2S removal, and complete NH3 separation. Exergy analysis shows minimal energy losses, highlighting its advantages over solvent-based techniques. The cost estimate further supports the approach's feasibility, indicating lower operating costs. This study offers a comparative assessment of syngas separation methods, with insights into energy efficiency and economic viability.
To mitigate the greenhouse effect, promoting the clean utilization of fossil fuels and advancing carbon capture, utilization, and storage (CCUS) technologies have become critical pathways. Among these approaches, CO2 and CH4 flooding, as key enhanced oil recovery (EOR) techniques, exhibit dual benefits in both emission reduction and production enhancement. In this study, molecular dynamics simulations are employed to systematically investigate the oil displacement behaviors of CO2 and CH4 in porous media reservoirs. Simulations are conducted under two temperature conditions: 300 K (ambient temperature) and 383 K (elevated temperature). The heat and mass transfer characteristics, as well as multiphase interaction mechanisms, are comparatively analyzed under three injection scenarios: CO2 single flooding, CH4 single flooding, and alternating CO2-CH4 injection. The results indicate that CO2 single flooding at 383 K achieves the highest molecular displacement fraction; however, it is accompanied by pronounced gas channeling. In contrast, under ambient temperature conditions (300 K), alternating injection exhibits significant synergistic effects. In particular, the alternating flooding strategy initiated with CO2 injection enhances molecular displacement fractions while effectively suppressing gas channeling compared with single-gas flooding. At elevated temperature, although alternating injection mitigates the risk of gas channeling, the increased gas diffusion coefficient weakens intermolecular interactions, leading to a reduced displacement efficiency relative to single-phase flooding. By establishing a multidimensional analytical framework that integrates temperature distribution, molecular interactions, and reservoir adsorption characteristics, this study elucidates the intrinsic mechanisms governing gas migration under multi-physical field coupling. The findings provide molecular-scale theoretical insights for optimizing gas injection strategies in unconventional oil reservoirs.
CO2 compression and liquefaction are critical process in carbon capture, utilization, and storage (CCUS) systems. However, CO2 streams obtained from capture sources often contain impurities such as N2, O2, and H2O, which significantly alter the thermophysical properties of pure CO2 and pose considerable challenges for system design and operation. In this study, the Peng-Robinson equation of state was employed within the Aspen HYSYS process simulation platform to systematically investigate the effects and mechanisms of these typical impurities on CO2 throughout the processes of compression, liquefaction, and pipeline transportation. The results reveal the quantitative influence of impurities on the thermodynamic properties, pipeline characteristics, and compression performance of CO2. N2 and O2 decrease the critical temperature and increase the critical pressure of the CO2 mixture, whereas H2O exhibits the opposite effect. In terms of thermodynamic properties, the density of CO2 is more sensitive to pressure variation, whereas viscosity and thermal conductivity are more sensitive to impurity concentration. N2 and O2 exhibit similar effects, whereas the influence of H2O on viscosity and thermal conductivity is negligible. During pipeline transportation, the presence of impurities intensifies pressure loss and pressure drop, with H2O exerting the most significant influence, whereas temperature distribution is only slightly affected. In the compression process, N2 and O2 increase the compressibility factor of CO2 and shift the compression path to the right on the pressure-enthalpy (p-H) diagram, leading to a considerable rise in compression energy consumption. The total energy consumption increases with impurity concentration. This study provides a solid theoretical basis and valuable data support for the optimized design, safe operation, and economic performance of industrial processes involving CO2 mixtures containing impurities.
