The underground storage of CO₂ in a depleted carbonate formation is a suitable method for limiting its anthropogenic release and minimize global warming. The rock wettability is an essential factor controlling the mechanisms of CO₂ trapping and its containment safety in the geo-storage formation. The geo-storage rock contains innate organic acids which alters the wettability of the rock surface from the hydrophilic condition to the hydrophobic state, thus reduce the CO₂ storage capacity. In this study, methyl orange which is a toxic dye that is generally released into environment was used as wettability modifier to change the wettability of stearic acid aged calcite (oil wet) to water wet. This study uses the contact angle technique (sessile drop method) to examine the effects of various concentration of methyl orange (10-100 mg/L) on the wettability of the CO₂/brine/stearic-acid aged calcite system under geo-storage conditions (i.e., temperatures of 25 and 50 ℃ and pressures of 5-20 MPa). The results indicate that the advancing and receding contact angles $({\theta }_a$ and ${\theta }_r)$ of the organic-acid contaminated rock surface were drastically reduced upon exposure to methyl orange, attaining the minimum values of 62° and 58° respectively, in the presence of 100 mg/L methyl orange at 20 MPa and 50 ℃. Thus, the present results suggest that rather than discharging methyl orange into the environment, it could be injected into underground reservoirs in order to reduce the level of environmental pollution and at the same time increase the CO₂ storage capacity of carbonate formations.

Gas injection into geological storage sites displaces existing water in rock pore spaces, triggering lateral secondary imbibition. This phenomenon involves the migration of water from areas with higher water saturation to replenish the displaced water. The lateral distance over which this imbibition occurs is critical for understanding injection/withdrawal flow rates and trapped-gas saturation during hydrogen and carbon dioxide geological storage. This study investigates secondary imbibition dynamics in hydrogen and carbon dioxide systems for calcite (representing carbonates) and basalt, considering pressure and temperature effects. Utilizing the modified Lucas-Washburn equation, the results reveal that lateral distance and secondary imbibition rates of water for all gas and rock systems decline with pressure. Additionally, the lateral distance and secondary imbibition rate of water for the hydrogen system at carbonates and basalts, and the carbon dioxide system at carbonates, increase with temperature. However, the lateral distance and secondary imbibition rate of water for the carbon dioxide system at basalts decrease with temperature. This research provides crucial fundamental data with significant implications for underground hydrogen storage and carbon dioxide geological storage. The findings contribute to the understanding of lateral imbibition in carbonate and basaltic rocks, offering valuable insights for enhancing gas retention within pore spaces, thereby influencing residual trapping.

Fossil fuels are the primary global energy source, and their improved production will ensure a balance between the increasing energy demand and supply. Chemical-enhanced oil recovery has been well thought of as a promising method for increasing hydrocarbon production. However, the effectiveness of this method depends on wettability of rock-oil-brine systems’ Previous studies have shown that oil-wet rock demonstrated a water-wet state when treated with surface active chemicals like surfactants, nanofluids. Moreover, increasing attention has become focused on the application of hazardous pollutants such as methyl orange and methylene blue to enhance the CO₂/H₂ containment security of the host rock by altering its wettability. Nevertheless, the capacity of methylene blue to modify the rock wettability for the production of trapped hydrocarbons in sandstone reservoirs is yet to be explored. Thus, in the present study, methylene blue is used as a wettability modifier to enhance the oil production from quartz rocks that have been aged with stearic acid solution (10-2 mol/L). First, the organic-aged quartz is treated with various concentrations of methylene blue (10-100 mg/L) for one week at 60 ℃. Then, contact angle measurements are performed at different temperatures (25 and 50 ℃) under various pressures (10-20 MPa) and brine salinities (0-0.3 M). Thus, the quartz is found to turn hydrophobic when aged in organic acid/n-decane solution at 20 MPa and 50 ℃. However, when the rock is treated with various concentrations of methylene blue, the hydrophobicity is found to decrease, thus suggesting that oil recovery will be promoted by methylene blue treatment. Overall, the results demonstrate that the most favourable condition for reducing the hydrophobicity of the sandstone rock is via treatment with 100 mg/L methylene blue. Hence, the injection of methylene blue into deep underground sandstone reservoirs has the potential to produce more residual hydrocarbons.

Underbalanced perforation can substantially reduce formation damage and improve the efficiency of production operation. The field in question is a giant oil field in Southwest Iran, with over 350,000 bbl/day production rates. Reservoir X is the main reservoir of the field and includes 139 horizontal wells out of the total of 185 production wells drilled in the field. Despite its technical difficulties, under-balance perforation has been proven to result in high productivity ratios and has been shown to reduce workover costs if appropriately conducted. Therefore, this study investigated a customized underbalanced tubing conveyed perforation to enhance oil production. First, post-drilling formation damage was estimated using Perforating Completion Solution Kits. Next, high-density guns (types 73 and 127) with high melting explosives were selected based on the reservoir and well specifications. By conducting a sensitivity analysis using schlumberger perforating analyzer program, shot angles of 60 ${}^{\circ }$ and 90 ${}^{\circ }$, shot densities of 16 and 20 shots per meter, perforation diameters of 8 and 10 mm, and helix hole distribution were selected as optimized perforation parameters and resulted in productivity ratios up to 1.18. The current study provides a case study of applying a combination of two previously proven technologies, tubing convoyed and underbalanced perforation, in Iran’s giant oilfield. The method used and the outcome could be used to analyze the efficiency of applying the technology in other green or mature fields.

Unconventional reservoir resources are important to supplement energy consumption and maintain the balance of supply and demand in the oil and gas market. However, due to the complex geological conditions, it is a significant challenge to develop unconventional reservoirs efficiently and economically. At present, unconventional reservoirs are extensively studied, covering a wide range of areas, with special attention to the multiscale characterization of pore structures and fracture networks, description of complex fluid transport mechanisms, mathematical modeling of flow properties, and coupled analysis with multiphysics fields. This work briefly describes the multiscale and multiphysics influences on fluids in unconventional reservoirs, and the modeling and simulation work conducted to analyze them, with the aim to provide some theoretical basis for enhanced recovery from these geo-energy resources. The present article also aims to enhance the community's knowledge of other potential utilizations associated with some unconventional reservoirs, specially related to environmentally-driven projects, including permanent greenhouse gas storage and cyclic underground energy storage.

Underground hydrogen storage has been recognized as a key technology for storing enormous amounts of hydrogen, thus aiding in the industrial-scale application of a hydrogen economy. However, underground hydrogen storage is only poorly understood, which leads to high project risk. This research thus examined the effect of caprock availability and hydrogen injection rate on hydrogen recovery factor and hydrogen leakage rate to address some fundamental questions related to underground hydrogen storage. A three dimensional heterogeneous reservoir model was developed, and the impact of caprock and hydrogen injected rate on hydrogen underground storage efficiency were analysed with the model. The results indicate that both caprock and injection rate have an important impact on hydrogen leakage, and the quantities of trapped and recovered hydrogen. It is concluded that higher injection rate increases H ${}_2$ leakage when caprocks are absent. In addition, lower injection rates and caprock availability increases the amount of recovered hydrogen. This work therefore provided fundamental information regarding underground hydrogen storage project assessment, and supports the decarbonisation of the energy supply chain.

Fully understanding the mechanism of pore-scale immiscible displacement dominated by capillary forces, especially local instabilities and their influence on flow patterns, is essential for various industrial and environmental applications such as enhanced oil recovery, ${\mathrm{CO}}_{\mathrm{2}}$ geo-sequestration and remediation of contaminated aquifers. It is well known that such immiscible displacement is extremely sensitive to the fluid properties and pore structure, especially the wetting properties of the porous medium which affect not only local interfacial instabilities at the micro-scale, but also displacement patterns at the macro-scale. In this review, local interfacial instabilities under three typical wetting conditions, namely Haines jump events during weakly-wetting drainage, snap-off events during strongly-wetting imbibition, and the co-existence of concave and convex interfaces under intermediate-wet condition, are reviewed to help understand the microscale physics and macroscopic consequences resulting in natural porous media.