Natural gas, an essential energy source, often contains undesirable acidic components such as hydrogen sulfide (H2S) and carbon dioxide (CO2), which must be removed to prevent corrosion, environmental pollution, and efficiency loss. During the dehydration of acid gases, the formation of carbonyl sulfide (COS) and elemental sulfur poses significant operational challenges, particularly in temperature swing adsorption (TSA) units using molecular sieves. Although COS is initially non-corrosive, it can hydrolyze to form H2S and CO2, exacerbating corrosion and reducing process reliability. In this study, molecular simulations using the RASPA (Version 2) code were employed to investigate the adsorption behavior of H2O, H2S, and CO2, and to explore the reaction pathways leading to COS and elemental sulfur formation in Na-LTA4A zeolite. The Langmuir–Freundlich model was applied to describe the adsorption isotherms, while the Aspen Adsorption (Version 12.1) software was used to simulate the TSA process under various operational conditions. Simulation results reveal that Na-LTA4A enhances H2S conversion to COS up to 81
Carbonate reservoirs pose substantial challenges for enhanced oil recovery (EOR) due to their inherently oil-wet surfaces and complex brine–rock interactions, necessitating environmentally benign yet high-efficiency solutions. To address this, a mechanistically designed ternary nanofluid system was developed, integrating Equisetum-derived nanosilica (NS), a novel cationic gemini surfactant (GS), and sulfate-enriched low-salinity brine (Na₂SO₄) to achieve multi-scale interfacial modification. Experimental procedures included comprehensive physicochemical characterization of the components, zeta potential and adsorption analyses, interfacial tension (IFT) measurements, contact angle (CA) evaluation, and spontaneous imbibition tests under controlled salinity conditions. Zeta potential results showed tunable surface charge from approximately − 70 mV to + 30 mV through sulfate-mediated adsorption and double-layer compression. The optimized ternary formulation achieved ultralow IFT of 0.51 mN/m at 5500 ppm Na₂SO₄ and significant wettability alteration with CA reduction from 138° to 34° at 2000 ppm Na₂SO₄. Langmuir adsorption modeling confirmed cooperative binding between NS and T14S3, and spontaneous imbibition demonstrated that the 2000 ppm Na₂SO₄ blend recovered 25.4
This study presented a procedure for predicting slope stability using four machine learning algorithms (extreme gradient boosting, support vector machine, logistic regression, and random forest). Based on a real-case database of 168 multinational slopes, this study analyzed the impact of six influential inputs: slope angle, friction angle, cohesion, height, pore pressure ratio, and unit weight. Notably, the results showed that the extreme gradient boosting algorithm surpassed other algorithms, achieving approximately 94
Background: The rising atmospheric CO2 levels, driven primarily by growing global energy demands, pose urgent climate challenges. In support of the International Energy Agency's ambitious carbon reduction goals, this study investigates CO2/ CH4 hydrate systems as a potential carbon capture solution. We specifically examine hydrate behavior under conditions mimicking deep-sea environments, with particular attention to sodium chloride's influence. Methods: Laboratory experiments employed a high-pressure system to analyze CH4 and CO2 hydrate equilibrium conditions in reservoir rock samples featuring 20 nm pores. The isochoric pressure-search method was applied to perform tests in saltwater solutions (3.5% NaCl). Key parameters-including concentration, pressure, and temperature-were rigorously controlled to accurately simulate hydrate formation and dissociation processes. Significant Findings: It was observed that increasing CO2 levels reduce the equilibrium pressure of CH4 + CO(2 )mixtures. The thermodynamic model used exhibited a strong predictive ability with an average absolute deviation of 3.38%. It was found that in nanopores (<20 nm), capillary forces govern hydrate formation while salinity effects become marginal, as evidenced by comparative water/salt system analyses. The study highlights the role of pore size, water salinity, and capillary pressures on hydrate stability, which are critical for improving CO2 sequestration methods and advancing natural gas recovery techniques.
Liquefaction, a crucial concern in geoengineering, is an imminent threat to infrastructures if the cyclic stress reduces effective stress to zero in the soil mass. This natural disaster relies on various factors. Scholars predominantly concentrate on the silica sands' liquefaction response, which contradicts that of carbonates. Few papers address contaminated carbonate sand liquefaction. Therefore, this investigation aims to study the liquefaction resistance of Bushehr carbonate sand (BCS) in clean, crude oil-contaminated, and treated conditions with eco-friendly techniques. The stabilization process uses natural zeolite, a novel material in geotechnical engineering, to stabilize oil-contaminated soils. Zeolite is a clean, safe, ample, and environmentally friendly material. The investigation uncovers that using 6 wt% zeolite has the most significant influence on the treatment of the liquefaction of BCS, yielding a 1.94-fold growth in the number of required cycles for triggering liquefaction. SEM and FTIR results verify the physical experiments, demonstrating that C-H bonds decrease sharply in zeolite-treated BCS specimens. This paper's findings reveal the significant role of zeolite's porous surface in the better adsorption of crude oil from the soil mass. This considerable adsorbing capacity causes outstanding improvement in cyclic strength, leading to a more convincing performance of this agent than other stabilization techniques suggested.
