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Sensitivity in polymer-bonded explosives (PBXs) relies on the presence of defects, such as cracks and voids, which create localized thermal energy, commonly known as hotspots, and initiate reactions through various localization phenomena. Our prior research has explored the use of internal gas pressure induced by thermite ignition to generate localized defects for PBX sensitization. However, further research is required to gain a more comprehensive understanding of the defect generation process resulting from internal gas pressure. This study investigates the process of defect generation in PBXs in response to internally induced gas pressure by applying controlled compressed gas to a fabricated cavity within the materials, simulating the gas pressure emitting from thermite. X-ray micro-computed tomography was employed to visualize the microstructure of the sample before and after gas injection. The experiments reveal the significance of gas pressure, cavity shape, temperature, and specimen compaction pressure in the defect generation. Numerical simulations using Abaqus/Standard were conducted to assess the defect generation in mock PBXs under varying gas pressures, cohesive properties, and binder thicknesses. The simulation results demonstrate the substantial influence of these properties on the ability to generate defects in mock PBXs. This study contributes to a better understanding of the factors influencing defect generation in mock PBXs. This knowledge is crucial for achieving precise control over defect generation, leading to improved ignition and detonation characteristics in PBXs. [ABSTRACT FROM AUTHOR]

The active injection system was designed to study the explosion flame propagation behavior of premixed CH 4 /H 2 /air mixtures in the closed tube with inert gas injection. The injection of inert gases (N 2 , CO 2 , and air) was controlled by the injection time, t inject , which is set from 0 ms to 210 ms. The effects of injection disturbance and inert gas dilution on flame morphology, flame tip dynamics, and overpressure build-up have been investigated. Results show that the injection of inert gas into premixed CH 4 /H 2 /air flame wrinkles the early laminar flame, changing the flame structure. The increase in t inject shortens the flame propagation time and increases the maximum explosion pressure, but the maximum value is attained at t inject = 120 ms. The linear relationship between maximum explosion pressure and maximum flame tip velocity is presented. The addition of inert gas dilutes the fuel-air mixture, but the inert gas shows some inhibition effect on the turbulent explosion flame propagation at t inject > 120 ms. The injection disturbance plays a dominant role in the flame propagation process compared to inert gas dilutions. Finally, the effect of Darrieus-Landau and Rayleigh-Taylor instabilities on explosion flame propagation behavior has been examined. The injection of inert gas into premixed CH 4 /H 2 /air flames creates local turbulence, enhances flame instabilities, and provides positive feedback on the flame's acceleration and oscillation. • Effect of inert gas injection on premixed CH 4 /H 2 /air explosions is investigated. • The injection disturbance plays a dominant role in explosion flame propagation behavior. • The injection of inert gas shortens flame propagation time and increases the explosion pressure. • Effect of inert gas type and injection time on explosion parameters are confirmed. • Injecting inert gas into the explosion flame changes the DL and RT instabilities. [ABSTRACT FROM AUTHOR]

As an efficient and clean energy, coalbed methane development and utilization have deep significance in promoting energy conservation and emission reduction, reducing greenhouse gas emissions. Therefore, molecular simulation was utilized to study the influence of N2/CO2 on the adsorption and diffusion of methane in coal under different gas injection methods and to elucidate the influence of varying gas injection methods on the efficiency of coalbed methane extraction, which provides a basis for the efficient development of coalbed methane. The results show that the adsorption effect of gases in coal decreases with the increase of temperature and increases with the rise of pressure, and the adsorption performance of the three gases in coal shows the law of CO2 > CH4 > N2. In addition, the injection of CO2/N2 had an obvious inhibition effect on CH4 adsorption, and the inhibition effect of CO2 was more significant, and the inhibition effect on CH4 adsorption reached the maximum when the two gases were mixture injected. In terms of diffusion, compared with separate injection, mixed injection of N2 + CO2 promotes CH4 diffusion more effectively, which can be reflected in the relative concentration distribution and velocity distribution. The injection of N2 helps to increase the porosity of coal, and the injection of CO2 and N2 + CO2 will lead to the decrease of porosity, but the mixed gas injection has less effect than the injection of CO2 alone. [ABSTRACT FROM AUTHOR]

The gas lift technique applies gas bubble injection into the vertical wells to raise production. Gas and liquid rates, shifts in flow regimes, and system equilibrium influence this process. This study explores the efficient implementation of gas lift techniques to maximize production from the Asmari Formation in the Abu Ghirab Field, southeastern Iraq, using a continuous gas lift for maximum production rate by PIPESIM TM software. The results of the gas lift design for the four wells (AGCS-33, 26, 28, and 36) show that the Vogel method provided the best results for the gas lift design, and faults and facies distribution impact the gas lift injection and oil production rates. These will become evident with wells AGCS-33 and 36 as their proximity to faults will increase oil production rates with a gas injection rate limit of 7 MMSCF/d. Conversely, for wells 26 and 28, the limit will marginally rise, starting at 5 MMSCF/d. In addition, the effect of gas lift is clearly in the middle western of the crest, which shows an increasing percentage of oil production of 136.6% at minimum rate and 198.5% at maximum for the well AGCS-26, 89.7% and 105.7% for the well AGCS-36. Wellhead pressure has a significant impact on gas-lift performance, and improving gas-lift efficiency can be accomplished using an electric control valve. The feasibility of implementing gas lift in the Asmari Formation depends on the water cut, well location, and water saturation distribution within the Formation. [ABSTRACT FROM AUTHOR]

The curtaining effect is a common challenge in focused ion beam (FIB) surface preparation. This study investigates methods to reduce this effect during plasma FIB milling of Inconel 718 (nickel‐based superalloy). Platinum deposition, silicon mask and XeF2 gas injection were explored as potential solutions. These methods were evaluated for two ion beam current conditions; a high ion beam intensity condition (30 kV–1 µA) and a medium one (30 kV–100 nA) and their impact on curtaining reduction and resulting cross‐section quality was assessed quantitatively thanks to topographic measurements done by atomic force microscopy (AFM). XeF2 assistance notably improved cross‐section quality at medium current level. Pt deposition and Si mask individually mitigated the curtaining effect, with greater efficacy at 100 nA. Both methods also contributed to reducing cross‐section curvature, with the Si mask outperforming Pt deposition. However, combining Pt deposition and Si mask with XeF2 injection led to deterioration of these protective layers and the reappearance of the curtaining effect after a quite short exposure time. LAY DESCRIPTION: The so‐called curtaining effect is a common challenge in focused ion beam (FIB) surface preparation. It is characterised by a relief occurring on the FIB prepared surface whereas a perfectly flat surface would ideally be expected. The issue of FIB‐induced curtaining effect represents a significant challenge in large‐scale 3D analysis applications, notably in methodologies reliant on FIB serial sectioning, such as 3D electron backscatter diffraction (3D EBSD). A strong curtaining effect can alter data quality and so their interpretation after 3D reconstruction. This study investigates methods to reduce this effect during plasma FIB milling of Inconel 718 (nickel‐based superalloy). Platinum deposition, silicon mask and XeF2 gas injection were explored as potential solutions. These methods were evaluated for two ion beam current conditions: a high ion beam intensity condition (30 kV–1 µA) and a medium one (30 kV–100 nA) and their impact on curtaining reduction, and resulting cross‐section quality was assessed quantitatively thanks to topographic measurements done by atomic force microscopy (AFM). XeF2 assistance notably improved cross‐section quality at medium current level. Pt deposition and Si mask individually mitigated the curtaining effect, with greater efficacy at 100 nA. Both methods also contributed to reducing cross‐section curvature, with the Si mask outperforming Pt deposition. However, combining Pt deposition and Si mask with XeF2 injection led to deterioration of these protective layers and the reappearance of the curtaining effect after a quite short exposure time. [ABSTRACT FROM AUTHOR]

The effect of external gas injection near the plume on the performance of a microwave discharge cathode is investigated. Experiments were conducted under two gas injection conditions: gas addition and gas distribution. Gas distribution tended to lead to better performance than gas addition. In the gas distribution experiments, the total gas consumption was kept constant, the internal gas flow rate was reduced, and external gas was supplied. The electron current increased from 0.26 to 0.49 A at 35 V when the microwave power was 15 W. When the sum of the internal and external gas flow rates was held constant, external gas injection lowered the neutralization costs and increased the gas utilization efficiency. The neutralization current was successfully increased by 48 % at 12 W of microwave power compared with 8 W of microwave power with the same level of naturalization cost and gas utilization efficiency. The electron temperature and plasma density in the plume, as measured using a Langmuir probe, suggested that an increase of ionization in the plume by the external gas injection enhanced the cathode's performance. • Supplying gas into the plume of a microwave discharge cathode improves its performance. • Neutralization current increased by 58 % with external gas injection. • External gas injection decrease naturalization cost and increase gas utilization efficiency. • An increase of ionization in the plume by the external gas injection enhanced the cathode's performance. [ABSTRACT FROM AUTHOR]

Low thermal evolution degree of gas and connected fracture network are key features in the continental shale gas reservoirs. When the pressure decreases lower than the dew point pressure, gas condensate diminishes the mobility of subsurface fluid forms in the near well region, which further reduces the productivity and final recovery factor in addition to the low connected fracture network. This work is motivated to investigate the application of gas injection, proven to be a feasible technique in conventional/marine-shale gas condensate reservoirs, in continental shale gas condensate reservoirs. We apply a compositional model to investigate the mechanism of gas injection treatment taking a continental shale gas condensate reservoir in the Fuxing area, Sichuan Basin, China as an example. The results demonstrate that for the removal of gas condensate during CO2 injection, re-vaporization plays the main mechanism through two processes including pressurization and development of miscibility, while the former is overwhelming. Considering the variation trend of the total volume of gas condensate, we divide the whole injection process into four and six stages in the single fracture model and fracture network model, respectively, and reason the trend with respect to phase behavior and flow pattern. A sensitive study on the injected gas type indicates that the sorting of the gas injection performance to remove gas condensate produced gas followed by CH4, and followed by CO2. Finally, we investigate the performance of cyclic produced-gas injection and optimize the injection scheme. This work provides technical and theoretical support for the development of continental shale gas reservoirs. [ABSTRACT FROM AUTHOR]

To study the smelting reduction behavior of methane in the HIsarna process, the isothermal reduction experiments of HIsarna slag with 6 wt% of FeO were conducted at the temperatures of 1450, 1475, and 1550 °C, using 5 vol% CH4‐Ar. The effect of the gas injection flow rate on the overall reduction rate was investigated in the range of 0.5–1.5 L min−1. The results confirm that the decomposed carbon black acts as the dominant reductant in the reduction process compared to hydrogen. Increased gas flow rate increases the reaction rate, while temperature shows no significant effect. The reduction process could be described by the JMAEK model: by fixing the gas flow rate at 1.0 L min−1 with different temperatures, the exponent n value is around 1.5, indicating FeO mass transfer is the limiting step since there are sufficient carbon blacks as nucleation sites. The reduction process follows the first‐order model controlled by the reactant concentration with the gas flow rate being at 0.5 L min−1 and in the second reaction stage of the gas flow rate at 1.5 L min−1. The determined activation energy for the methane reduction is 59.8 kJ mol−1. [ABSTRACT FROM AUTHOR]

The use of foam injection as an enhanced oil recovery (EOR) technique has been suggested since the 1960s to address issues with gas injection. Foam is composed of gas, water, and surfactant, which is utilized to stabilize the foam. This study investigates the synergy effect of anionic surfactant and two zwitterionic surfactants on enhancing solution stability. The anionic surfactant used is sodium dodecyl sulfate, while the chosen zwitterionic surfactants are cocamidopropy hydroxy sultine and Cocamido Propyl Betaine. Analyzing the images of the generated foam showed that initially, the small and uniform bubbles are formed in all concentrations. The foam size is then increased and in concentrations higher than a critical value, the bubbles grow faster which is likely due to the formation of micelles and deposition of surfactants. This leads to early collapse of the foam structure. The quantitative half-life results approved that the most optimal compound was obtained with equal proportions of sodium dodecyl sulfate and Cocamido Propyl Betaine with concentration of 3 wt% (1:1 ratio, 0.15 wt%-0.15 wt%). To quantitatively study on foam characteristics, conductivity and interfacial tension tests were performed. The results of the conductivity tests showed that micelles were formed in concentrations of more than 0.3 wt%. Interfacial tension measurements revealed that addition of a small amount of surfactants to the base solution, led to reduction of the interfacial tension value from 29.2 (mN/m) in base solution to less than 1 mN/m for solutions treated with surfactant. [ABSTRACT FROM AUTHOR]

The power to gas (P2G) equipment serves as a critical linkage in integrated energy systems that foster bidirectional energy flow to enhance the share of renewable energy and curb uncertainty. By bringing together P2G hydrogen production and hydrogen injection into gas grid technology, the energy conversion loss associated with P2G applications can be significantly reduced. Nonetheless, the strict criteria concerning hydrogen blending ratios pose limitations on the integration of renewable energy. This paper proposes a comprehensive energy system model that couples gas grid hydrogen injection with a hybrid P2G process, aiming to reduce energy conversion losses and overcome the constraints posed by hydrogen blending ratios. This approach promotes the efficient utilization of renewable energy in integrated energy systems (IES). For wind power uncertainty, a scenario analysis method combining Latin hypercube sampling and scenario curtailment 0–1 algorithm is employed. The model's nonlinear constraints are linearized through piecewise linearization, transforming the problem into a mixed-integer programming one for solution simulation results demonstrate that the application of the hybrid P2G process in IES systems with hydrogen injection into gas grid technology reduces certain energy conversion stages and cost inputs compared to using only power to hydrogen conversion. This approach shows significant improvements in economic and environmental performance. The hybrid P2G scheme reduces the hydrogen blending ratio of the system to the minimum operating cost from 12 % to 6 %. At the same time, its minimum value is 20.1 thousand USD lower than that of the scheme using only power to hydrogen conversion, which is about 4.7 % of the total cost. [Display omitted] • An IES based on hybrid P2G and hydrogen injection into gas grid is proposed. • The conversion rate is used to analyze the effect of renewable energy consumption. • The 0–1 algorithm is used to curtailment scenarios to capture the uncertainties. • A multi-scenario model is constructed to optimize capacities and operation. • The optimal economic performance is achieved at the hydrogen blending ratio of 6 %. [ABSTRACT FROM AUTHOR]

With the development of the petroleum industry and advancements in technology, gas injection techniques have gradually matured and become an important means to enhance oil recovery in reservoir development. Gas channeling is a major challenge in the process of gas injection development. The presence of gas channeling can lead to a decrease in the swept volume of gas flooding, severely affecting the effectiveness of gas injection development. This paper focuses on low-permeability reservoirs, comprehensively analyzing the development characteristics of low-permeability reservoirs and the dynamic characteristics of gas flooding production. It selects and evaluates indicators for assessing the development degree of gas channeling and establishes a fuzzy comprehensive evaluation method for evaluating gas channeling in the gas injection development of low-permeability reservoirs. Based on the evaluation values derived from the fuzzy comprehensive evaluation, it classifies the development levels of gas channeling. Application in oilfield cases shows that the evaluation results of this method are generally consistent with the dynamic response of production data, with high evaluation accuracy. This provides strong support for implementing gas channeling prevention and control measures on site and improving the effectiveness of gas injection development. [ABSTRACT FROM AUTHOR]

CO2-enhanced oil recovery (CO2-EOR) is a crucial method for CO2 utilization and sequestration, representing an important zero-carbon or even negative-carbon emission reduction technology. However, the low viscosity of CO2 and reservoir heterogeneity often result in early gas breakthrough, significantly reducing CO2 utilization and sequestration efficiency. A water-alternating-gas (WAG) injection is a technique for mitigating gas breakthrough and viscous fingering in CO2-EOR. However, it encounters challenges related to insufficient mobility control in highly heterogeneous and fractured reservoirs, resulting in gas channeling and low sweep efficiency. Despite the extensive application and research of a WAG injection in oil and gas reservoirs, the most recent comprehensive review dates back to 2018, which focuses on the mechanisms of EOR using conventional WAG. Herein, we give an updated and comprehensive review to incorporate the latest advancements in CO2-WAG flooding techniques for enhanced sweep efficiency, which includes the theory, applications, fluid displacement mechanisms, and control strategies of a CO2-WAG injection. It addresses common challenges, operational issues, and remedial measures in WAG projects by covering studies from experiments, simulations, and pore-scale modeling. This review aims to provide guidance and serve as a reference for the application and research advancement of CO2-EOR techniques in heterogeneous and fractured reservoirs. [ABSTRACT FROM AUTHOR]

In order to analyse the effect of the injection point size of the CBM (Coalbed Methane) well level monitor on the amplitude and frequency of pressure pulsations in the wellhead manifold, numerical simulations and experiments were carried out to investigate the effect of different injection point sizes on the amplitude and frequency of pressure pulsations downstream of the sudden expansion structure. Using compressed air as the fluid and the size of the injection point as the variable, the amplitude and frequency of pressure pulsations at different locations downstream of the sudden expansion structure were tested. The results show that the pressure pulsation amplitude is affected by the size of the injection point, and the larger the injection point is, the larger the pressure pulsation amplitude is; the size of the injection point has less influence on the pressure pulsation frequency downstream of the protruding and expanding structure, and the pressure pulsation frequency at 0.5 m and 1 m downstream of the protruding and expanding structure is in the vicinity of 76 Hz. Therefore, the echo signal processing should be filtered around this frequency to obtain accurate liquid level echo signals, so as to improve the accuracy of liquid level monitoring and realise the efficient development of coalbed methane wells. [ABSTRACT FROM AUTHOR]

The production and utilization of hydrogen (H 2) as a clean energy source offer a promising solution towards achieving net-zero carbon emissions. Utilizing sandstone formations for geological hydrogen storage presents a viable option for the practical implementation of the hydrogen economy, offering both safe and large-scale containment capabilities. Accurate assessment of gas displacement behavior in porous media plays a critical role in understanding gas saturation, gas residual, and long-term storage duration. However, there are limited studies available on dynamic displacements for hydrogen storage applications. This study aims to enhance the understanding of gas flow behavior in sandstone rocks for different gas types and determine the role of capillary pressure and gas wettability during hydrogen storage. A series of gas core-flooding experiments are performed on a brine-saturated sandstone core sample using three different gases (CO 2 , CH 4, and H 2). X-ray scanning technique is applied to detect the gas saturation and gas residual after the core-flooding experiments. The results indicate that the average gas saturation ranges between 25 and 40%, with zero gas residual for all gases, suggesting that the gas residuals in this clean sandstone sample are unaffected by the gas type. Initially, the capillary pressure profile for the sample displayed low brine saturation at 200 psi, indicating very low capillary pressure in the sample due to the high permeability and large pore radius, despite the strong water-wetting behavior of the sample. Moreover, the obtained results indicate the high potential for gas recovery (especially for hydrogen during withdrawal cycles), and the high displacement efficiency in sandstone rocks. The reported low gas residual suggests that the wettability of the rock is not affected by gas injection, and it appears that the wettability and capillary pressure are not the controlling factors for gas storage in this sandstone sample. This observation suggests that the structural trapping mechanism is most likely to be the dominant trapping mechanism in this shallow high permeable sandstone rock. Also, the injection of cushion gases such as CO 2 and CH 4 indicated similar results to hydrogen injection, due to the low capillary pressure and high permeability in this sandstone sample. The findings of this study can greatly enhance the understanding of gas injection, displacement behavior, and gas residuals in sandstone rocks related to underground hydrogen storage. • The behavior of gas injection and dynamic displacements in sandstone reservoirs are investigated vis X-ray core-flooding. • CO 2 displayed an average gas saturation of 40%, while the average gas saturation for H 2 and CH 4 ranged between 25 and 30%. • The residual gas saturations in the sample were almost zero for all gases. • The rock wettability was not affected by gas injection. • Structural trapping mechanism appears to be the dominant trapping mechanism for shallow high-permeable sandstone rocks. [ABSTRACT FROM AUTHOR]

Gas injection is a well-known method for enhancing oil recovery (EOR). The utilization of greenhouse gases, such as carbon dioxide (CO2) or flue gas, offers the dual advantage of reducing greenhouse gas emissions while potentially enhancing the sweep efficiency in oil recovery. Nevertheless, one of the notable challenges encountered when using these gases is the precipitation and deposition of asphaltenes, leading to formation damage and a decrease in reservoir permeability, particularly in the case of light oil reservoirs. In this study, CO2 and flue gas were injected into an elongated core sample comprising four individual core plugs under reservoir conditions to displace the light live oil. The recovery factor and asphaltene deposition along the core holder were assessed and compared as two crucial parameters within the gas injection scenario. Our results indicate a significantly higher recovery factor of 86% achieved with CO2 injection compared to 36% with flue gas injection, attributable to differences in their interfacial tension and miscibility. However, the CO2 injection method exhibits more pronounced formation damage. Individual assessment of each core plug reveals that permeability impairment is most acute in the initial two core plugs, situated closer to the injection face of the extended core. These findings enhance our understanding of the mechanisms contributing to permeability impairment resulting from asphaltene deposition during CO2 and flue gas injection for EOR. [ABSTRACT FROM AUTHOR]

Gas injection displacement is a widely used technique to enhance the recovery of coal methane (CH4) or oil reservoirs. Additionally, this method plays a crucial role in effectively developing CH4 resources in a closed goaf. In the present study, the distribution characteristics of fissures in a closed goaf were determined using a physical simulation test, and the connected fissure network was extracted and modeled. Further, CH4 extraction numerical simulation tests were conducted on the connected fissure network under gas injection conditions. The migration and distribution characteristics of CH4 were analyzed in the connected fissure network under different gas injection conditions, including gas injection position, gas injection rate, and gas injection type. The research also evaluated the impact of different gas injection conditions on CH4 production in vertical wells. Finally, a model was developed to determine characteristic parameters for CH4 production in vertical production wells, which were calculated and compared across different gas injection conditions. Results revealed a negative correlation between CH4 volume fraction and gas injection time in vertical wells under different gas injection conditions, contrary to the S-type growth curve. Gas injection positions significantly influenced the migration and distribution of gas within the connected fissure network, with higher CH4 productivity and production efficiency in the gas injection position P2 compared to P1. The increase in the gas injection rate enhanced CH4 production efficiency, albeit having little effect on CH4 productivity. Gas injection types yielded no significant influence on CH4 production efficiency, although CH4 productivity was lower with 100% CO2 injection compared to 100% N2 and mixed gas. This investigation provides the foothold for enhancing the recovery of CH4 in closed goafs and contributes to the progress of carbon emission reduction technology in coal mining areas. [ABSTRACT FROM AUTHOR]

A continuous injection of gaseous water propellant into a magnetron-type sputtering propulsion device is performed in a pseudo manner by using a combination of two high-speed solenoid-type pulsed valves and a low-pressure gas reservoir. The gas injection system provides a temporally averaged gas flow rate of about 5–10 sccm with adjustment of the repetition frequencies of the pulsed valves, while the previously used single valve system attached to a liquid water tank has caused excessive gas injection. A discharge is sustained by a high voltage dc power supply; the discharge current has pulsation synchronized with the pulsed valve repetition. A temporally averaged force induced by the magnetron sputtering thruster and exerted on a pendulum plate downstream of the thruster is measured; the results are in good agreement with the previously reported force measurement under precisely controlled gas flow rate using a commercial mass flow controller. Therefore, the precise control of the gaseous water propellant with the compact gas feeding system is achieved, while maintaining a similar thruster performance to that with the mass flow controller. • The double pulsed valves system provides the precise control of the gaseous water. • The magnetron sputtering thruster is properly operated with the pulsed valves system. • The thrust-to-power ratio of 3–4 mN/kW is obtained. [ABSTRACT FROM AUTHOR]

Foam can effectively improve reservoir heterogeneity, increase gas–liquid flow rate, reduce viscous fingering, and help to improve sweep efficiency. This paper mainly studies the characteristics and performance of microbial foam production, and proposes an enhanced oil recovery method for profile control by in situ microbial foam production. By optimizing the carbon and nitrogen sources of the medium, Pseudomonas aeruginosa PAO1 produced single and double rhamnolipids and biogas composed of N2, CO2, and CH4, and it could also produce foam in high salt, weak acid, and weak alkali environments. Gas injection experiments were carried out using self-produced biogas, the foaming effect is good in the range of gas–liquid ratio 1:1–3:1 and gas injection speed 20–40 ml/min, which was 71.43%–91.25% more than the foam volume produced by CO2 injection, and the foam production was positively correlated with the protein concentration of the foam. In the early stage of incubation, the foam was 20–100 μm in diameter, with high protein concentration and strong foam stability, which slowed down the drainage, polymerization, and disproportionation of the liquid film of the foam system. The foam performance test results show that the foam half-lifetime is long, up to 109 min. Foam culture medium has good viscosity reduction effect, emulsifying properties and less corrosive. The displacement experiment shows that the foam generated in situ by PAO1 in the core has good stability, reproducibility, and profile control performance, which can reduce the permeability of the core to half of the initial permeability and improve the reservoir heterogeneity. Therefore, microbial in situ foam production can be an effective method to enhance oil recovery in heterogeneous reservoirs, which is low cost, low pollution, and simple operation. [ABSTRACT FROM AUTHOR]

Oscillation characteristics in a cavity are investigated under real experimental conditions through unsteady numerical simulations of the time-evolving oscillatory damping of a high-Mach-number freestream over a two-dimensional forward-facing cavity. The post-disturbance flow field is taken as the initial condition. Temporal variations in the flow field and wall resistance coefficient are obtained. The forward-facing cavity experiences underdamped oscillatory behavior when subjected to disturbances. The convergence of the oscillations is influenced by the cavity volume, with significant reductions in cavity damping observed when stagnation regions develop within the cavity. During the initial phase of disturbance, each oscillation cycle consists of gas injection and jet phases. In the former, external gas stagnates within the cavity, resulting in a gradual increase in internal density and pressure. High-temperature regions extend from the external flow into the cavity, and bow shocks approach the cavity wall, adversely affecting aerodynamic drag reduction and thermal protection for aircrafts. In the jet phase, the flow field structure resembles the opposing jet. As the gas is expelled, the internal cavity pressure decreases, forming a cold jet that envelops the cavity's surface. The temperature within the boundary layer on the surface decreases, and bow shocks are pushed away from the wall, resulting in thermal-protection and drag-reduction effects. Transitions between phases induce instability in the internal flow states within the cavity. During the transition from the gas injection phase to the jet phase, the wall drag coefficient reaches its peak value; the reverse transition results in the lowest wall drag coefficient. [ABSTRACT FROM AUTHOR]

Effects of secondary gas injection on flame shape and combustion stability of a premixed swirl methane/air flame were investigated experimentally. Without secondary gas injection, an attached M-shaped flame was observed with pressure oscillations up to a sound pressure level of 68 dB. The flame exhibited significant oscillations due to flame–vortex interactions induced by velocity fluctuations. The secondary methane or air was separately injected into the outer recirculation zone to suppress the flame oscillations at a volume flow rate of 0.5% of the primary flow rates. For lower primary air flow rates ( Q air ≤ 60 L/min), both secondary methane and air injections were able to suppress the thermoacoustic instability and performed the sound pressure level reduction of 45 dB. Meanwhile, the flame transformed from an attached unstable M-shaped flame to a detached stable V-shaped flame. The secondary methane or air injection served to stabilize the flame and anchor its spatial heat release distribution by limiting the variation of flame shape in the outer recirculation zone, suppressing thermoacoustic oscillation. For higher primary air flow rates ( Q air = 80 L/min), the secondary methane injection could reduce sound pressure levels to noise levels, while secondary air injection could not. The velocity disturbances and heat release fluctuations introduced by secondary methane injection could lead to a transformation in flame shape and achieve the suppression of thermoacoustic oscillation. However, the velocity disturbances induced by secondary air injection were insufficient to stabilize the flame. [ABSTRACT FROM AUTHOR]

Background: Dark eye circle (DEC) is one of the most common cosmetic problems. It has a great impact on the patients' quality of life. Carboxytherapy is a cosmetic technique using pure carbon dioxide for different uses in different areas of the body. The goal of this study is to evaluate the efficacy and tolerability of carboxytherapy in the cosmetic correction of DECs. Methods: This study was conducted on 27 patients requesting the correction of DEC. The treatment was performed using a carboxy device in medical grade. The gas injection was performed intradermal after local anesthesia, with a pressure of one tenth bar and a speed of 20 cc/min, 1 cc in each upper and lower eyelid. The treatment sessions were done every 2 weeks for four sessions. Results: The mean physicians' score of DECs before and after treatment was 8.7 ± 0.81 and 4.6 ± 1.1, respectively. The mean patients' score before and after treatment was 9.2 ± 0.5 versus 5.41 ± 1.37. The mean scores showed a significant reduction of skin discoloration without major side effects (p < 0.00001). Conclusion: Carboxytherapy seems to be an effective treatment option for dark circles around the eyes with a good safety profile and patient satisfaction. [ABSTRACT FROM AUTHOR]

The clastic reservoir in Tarim Oilfield has entered the middle-to-late stage of development, and consequently, enhanced oil recovery (EOR) is becoming highly challenging. Gas flooding is the practical method for EOR from this type of reservoirs. In this study, taking Tazhong 402 CIII reservoir as an example, the micro-mechanism of EOR by gas injection is investigated by conducting slim-tube, long-core displacement, and micro-visual displacement experiments. A gas injection development plan is formulated based on reservoir characteristics, laboratory experiments, and numerical simulations. The results show that miscible flooding cannot be achieved by injecting natural gas under the current formation conditions; however, natural gas flooding after light hydrocarbon flooding can significantly improve oil recovery. The studied reservoir is divided into two series of development layers: CIII1–3 layers, for which light hydrocarbon alternating natural gas flooding is adopted, and CIII4–8 layers, for which light hydrocarbon combined with natural gas gravity-assisted composite flooding is employed. The findings of this study have guiding significance for gas injection development in deep clastic reservoir in Tarim Basin. [ABSTRACT FROM AUTHOR]

Gas injection for enhanced oil and gas reservoir recovery is a crucial method in offshore Carbon Capture, Utilization, and Storage (CCUS). The B6 buried hill condensate gas reservoir, characterized by high CO2 content, a deficit in natural energy, developed fractures and low-pressure differentials between formation and saturation pressures, requires supplementary formation energy to mitigate retrograde condensation near the wellbore area through gas injection. However, due to the connected fractures, the B6 gas reservoir exhibits strong horizontal and vertical heterogeneity, resulting in severe gas channeling and a futile cycle, which affects the gas injection efficiency at various levels of fracture development. Based on these findings, we conducted gas injection experiments and numerical simulations on fractured cores. A characterization method for oil and gas relative permeability considering dissolution was established. Additionally, the gas injection development boundary for this type of condensate gas reservoir was quantified according to the degree of fracture development, and the gas injection mode of the B6 reservoir was optimized. Research indicates that the presence of fractures leads to the formation of a dominant gas channel; the greater the permeability difference, the poorer the gas injection effect. The permeability gradation (fracture permeability divided by matrix permeability) in the gas injection area should be no higher than 15; gas injection in wells A1 and A2 is likely to achieve a better development effect under the existing well pattern. Moreover, early gas injection timing and pulse gas injection prove beneficial in enhancing the recovery rate of condensate oil. The study offers significant guidance for the development of similar gas reservoirs and for reservoirs with weakly connected fractures; advancing the timing of gas injection can mitigate the retrograde condensation phenomenon, whereas initiating gas injection after depletion may reduce the impact of gas channeling for reservoirs with strongly connected fractures. [ABSTRACT FROM AUTHOR]

Evaluating underground gas storage (UGS) sealing capacity is essential for its safe construction and operational efficiency. This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal, and alternating loads. This study detailed the methodology developed by Sinopec. The approach merges disciplines like geology, geomechanics, and hydrodynamics, employing both dynamic-static and qualitative-quantitative analyses. Sinopec's evaluation methods, grounded in the in situ stress analysis, include mechanistic studies, laboratory tests, geological surveys, stress analysis, and fluid-solid interactions. Through tests on the static and dynamic sealing capacity of UGS, alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults, A geomechanics - rock damage - seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity, thereby setting the maximum operational pressures. Utilizing this evaluation technique, Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs, enabling preliminary sealing capacity evaluations at UGS sites. These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations. [ABSTRACT FROM AUTHOR]

BACKGROUND: At present, there are few studies on the technical requirements of manual bedside placement of post-pyloric tube in Intensive Care Unit patients. OBJECTIVE: To investigate the application value of downward tract adherence method in the manual bedside placement of jejunal tubes. METHODS: In the downward group, 160 patients underwent manual bedside placement of jejunal tubes by a downward tract adherence method. In the conventional group, 144 patients were treated with conventional gas injection during the placement. The success rate, average time, and adverse reactions of the placement in the two groups were investigated and compared. RESULTS: The success rate of the placement in the downward group was significantly higher (95% vs. 75%, P < 0.001) and the average time for the successful placement was shortened (23 ± 5.91 min vs. 26 ± 5.49 min, P = 0.025) than that in the conventional group. No treatment-related adverse reactions occurred in either group, and there were also no significant differences in vital sign changes. CONCLUSIONS: The use of the downward tract adherence method in the manual bedside placement of postpyloric tubes for the intensive care patients at the bedside has a higher success rate, effectivity and safety. [ABSTRACT FROM AUTHOR]

Adjusting injection and production parameters is an essential tool for studying the effect of reservoir heterogeneity on in-situ combustion (ISC) sweep and associated control strategies, as well as for achieving stable ISC. An asynchronous injection and production in-situ combustion (AIPISC) method through the coupling of the gas injector and producer in order to accomplish the balanced sweep of ISC. Using the Hongqian (HQ) ISC in Xinjiang as an example, numerical simulation was utilized to define the reservoir and investigate the sweep characteristics under various sedimentary models. The AIPISC technology was applied to several heterogeneous reservoirs, and the design scheme of AIPISC was created. Under the same heterogeneous reservoir circumstances as the conventional ISC approach, the oil saturation of the AIPISC wall increases from 0.65 to 0.72. The roundness of the combustion chamber was better, and balanced displacement can be achieved. Then the parameters of AIPISC were optimized to determine that the vertical permeability difference of the reservoir should be less than 15, the asynchronous time difference was 6 ∼ 8 months, and the gas injection amplitude was 1.5 ∼ 2.0. The results show that the experiment in HQ Oilfield was successful, and the usefulness of AIPISC was investigated using the electromagnetic approach. [ABSTRACT FROM AUTHOR]

Enhanced coalbed methane (ECBM) recovery by gas injection is regarded as a feasible method for ECBM recovery. To investigate the mechanism of CH4 displacement by N2 injection, a series of physical experiments were conducted in the laboratory under different N2 injection pressures. The experimental results showed a continuous increase in the N2 volume fraction and a decrease in the CH4 volume fraction with the N2 injection pressure. The CH4 displacement efficiency increases rapidly in the initial stage and then gradually stabilizes. Given the effect of matrix shrinkage and effective stress on coal permeability, a dynamic multi‐field coupling model of ECBM recovery by N2 injection (N2‐ECBM) was proposed in this work. Then, numerical simulations were implemented by the coupling model to analyze the key factors affecting coal permeability, N2 injection pressure and CH4 pressure during the N2–ECBM process. Furthermore, the Response Surface Methodology (RSM) was used to investigate the interactions of multiple factors, the results reveal that an increase in one factor would weaken the influence of another factor. In addition, a RSM regression model was obtained and verified by the experimental data, with a well‐fitting outcomes. Therefore, the RSM model can be used in practical engineering applications to optimize specific extraction parameters for ECBM recovery at minimum cost in a limited extraction period. [ABSTRACT FROM AUTHOR]

Gas distribution networks traditionally maintain constant pressure setpoints at regulating stations, ensuring a consistent supply to end-users with a high safety margin. However, the prospect of hydrogen injection in the gas networks necessitates rethinking operational strategies. This study examines the environmental and fluid-dynamic implications of implementing a smart pressure management approach in regulating stations within a distribution network with a localized hydrogen injection. The research introduces a novel simulation-based optimization algorithm, incorporating a steady-state fluid-dynamic model with hydrogen tracking, used to optimize the pressure setpoints in the stations. The algorithm is applied to a two-pressure levels looped gas network with multiple gas supply nodes and a single hydrogen injection. The test case results reveal that utilizing dynamic pressure setpoints leads to a 22% increase in hydrogen penetration compared to standard operation. Therefore, this study highlights that smart pressure modulation in a gas network with hydrogen injection can unlock a latent decarbonization potential, while simultaneously adhering to safety limits. [Display omitted] • Pressure modulation can increase hydrogen absorption in a distribution network. • Pressure modulation influences the gas flows in the network. • The modulation range is larger when the demand is higher. • At peak demand hydrogen injection is constrained by the node with the minimum pressure. • At minimum demand hydrogen injection is constrained by the gas quality constraint. [ABSTRACT FROM AUTHOR]

Due to the increasing world population and environmental considerations, there has been a tremendous interest in alternative energy sources. Hydrogen plays a major role as an energy carrier due to its environmentally benign nature. The combustion of hydrogen releases water vapor while it also has a vast industrial application in aerospace, pharmaceutical, and metallurgical industries. Although promising, hydrogen faces storage challenges. Underground hydrogen storage (UHS) presents a promising method of safely storing hydrogen. The selection of the appropriate cushion gas for UHS is a critical aspect of ensuring the safety, efficiency, and reliability of the storage system. Cushion gas plays a pivotal role in maintaining the necessary pressure within the storage reservoir, thereby enabling consistent injection and withdrawal rates of hydrogen. One of the key functions of the cushion gas is to act as a buffer, ensuring that the storage pressure remains within the desired range despite fluctuations in hydrogen demand or supply. This is achieved by alternately expanding and compressing the cushion gas during the injection and withdrawal cycles, thereby effectively regulating the overall pressure dynamics within the storage facility. Furthermore, the choice of cushion gas can have significant implications on the performance and long-term stability of the UHS system. Factors such as compatibility with hydrogen, cost-effectiveness, availability, and environmental impact must be carefully considered when selecting the most suitable cushion gas. The present study provides a comprehensive review of different types of cushion gases commonly used in UHS, including nitrogen, methane, and carbon dioxide. By examining the advantages, limitations, and practical considerations associated with each option, the study aims to offer valuable insights into optimizing the performance and reliability of UHS systems. Ultimately, the successful implementation of UHS hinges not only on technological innovation but also on strategic decisions regarding cushion gas selection and management. By addressing these challenges proactively, stakeholders can unlock the full potential of hydrogen as a clean and sustainable energy carrier, thereby contributing to the global transition towards a low-carbon future. [ABSTRACT FROM AUTHOR]

In the geological disposal of high-level radioactive waste in argillaceous rocks, studying the barrier integrity after gas transport and the pathway closure thanks to self-sealing capacity is a crucial aspect for the safety assessment. This paper presents experimental research in Boom Clay (a potential host rock in Belgium) to evaluate the effectiveness of self-sealing and possible fissure reactivation during a second gas invasion event. Initial water permeability under oedometer conditions was first measured on samples at two bedding orientations, being higher the sample with bedding planes parallel to flow, highlighting marked anisotropy. Then, gas injection tests at a constant volume rate were performed. Results indicated that Boom Clay underwent expansion and degradation during gas injection due to the development of fissures that were quantified using microstructural techniques. The computed effective gas permeability was not significantly dependent on bedding orientation and was slightly larger than the initial intrinsic water permeability. The re-saturation of the samples led to a recovery of the initial water permeability for both orientations, replicating the original anisotropy. The microstructural analyses confirmed the gas pathways' closure, indicating good self-sealing and the regaining of the hydraulic barrier function. However, a small volume of large unconnected pores was detected on undrained unloading before the microstructural study. An additional gas injection after the self-sealing resulted in a higher effective gas permeability and a larger increase in pore volume, suggesting the reopening of fissures generated during the first injection. Finally, the experimental data were compiled within a multi-scale phenomenological model to relate the microstructural information to macroscopic flow transport properties capturing the intrinsic permeability increase on gas invasion and its recovery during self-sealing. Highlights: Gas transport on Boom Clay occurs along fissures, increasing its permeability The re-saturation process induces the recovery of the initial water permeability, demonstrating an excellent self-sealing capacity. A subsequent gas injection after the re-saturation suggests the reopening of previous gas paths. A multi-scale model is proposed to account for the permeability changes derived from a microstructural damage variable. [ABSTRACT FROM AUTHOR]

To analyze the self-sealing process in the Callovo-Oxfordian claystone, self-sealing tests were performed on initially fractured samples under different temperatures with water and gas injection. Cylindrical samples oriented in parallel and perpendicularly to the bedding plane with an artificial initial fracture were used in a triaxial compression cell transparent to X-rays. Water and gas permeability were measured and the evolution of cracks volume was analyzed from X-ray tomography 3D images to characterize the self-sealing process. All tests performed at 20 °C with water injection showed a rapid drop in permeability at the beginning followed by a progressive decrease and a stabilization after one month. The permeability of fractured samples decreases significantly after self-sealing but is still higher (by 2 orders of magnitude) than the permeability of healthy claystone. Otherwise, the less calcite the sample contains (i.e., the more clayey it is), the faster the crack self-seals. The smaller the opening of the initial crack is, the faster the water permeability decreases and the crack closes. No significant influence of the sample orientation on the self-sealing kinetic was identified at this stage. It seems that high temperature has a slight retarding effect on the self-sealing process. For the test with water and gas injection, the injection of gas delays the decrease of water permeability and the self-sealing process, which is probably due to the crack desaturation induced by gas injection. Highlights: Self-sealing tests were performed on initially fractured samples of Callovo-Oxfordian claystone with different temperatures, orientations and fluids (water, gas). Self-sealing process was analyzed thanks to permeability measurements and crack volume estimation from X-ray tomography 3D images. The self-sealing process is fast at the beginning of the test and stabilizes after about one month and the initial permeability of the healthy rock is partially restored. The less calcite the sample contains (the more clayey it is) and the smaller the opening of the initial crack is, the faster the crack self-seals. Temperature and gas seem to have a delay effect on the self-sealing process. There is no significant influence of the sample orientation. [ABSTRACT FROM AUTHOR]

Since hydrate resources play a part of the stratigraphic framework structure in sediments, establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day. Among the proposed methods, the spontaneous displacement of CH4 from hydrate cages by CO2 seems to be a perfect mechanism to address gas production and CO2 storage, especially in today's strong demand for carbon reduction and replacing clean energy. After extensive lab researches, in the past decade, injecting a mixture of CO2 and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application. However, there is a lack of in-depth research on gas flow in the reservoir, while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term, finally resulting in the decreases in gas production efficiency and produced gas quality. Therefore, we explored a new injection-production mode of alternate injection of N2 and CO2 in order to fully coordinate the advantages of N2 in enhanced hydrate decomposition and CO2 in solid storage and heat compensation. These alternate "taking" and "storing" processes perfectly repair the problem of the gas channel, achieving self-regulation effect of CH4 recovery and CO2 storage. The 3-D experimental results show that compared to the mixed gas injection, CH4 recovery is increased by >50% and CO2 storage is increased by >70%. Additionally, this alternate injection mode presented a better performance in CH4 concentration of produced gas and showed outstanding N2 utilization efficiency. Further, we analyzed its self-adaptive gas flow mechanism and proposed an application model of "one injection and multiple production". We look forward to this study accelerating the application of CO2-CH4 replacement technology. [ABSTRACT FROM AUTHOR]

For field development and drilling decisions, production assets and reservoir engineers require dynamic reservoir properties, such as saturation and pressure changes of a reservoir from the pre‐production virgin state. To date, geophysicists have produced time‐lapse (4D) seismic attributes (mostly on stacked seismic data) rather than dynamic parameters directly. In this paper, we present a new method to estimate saturation and pressure properties from time‐lapse seismic data to provide to reservoir engineers. This new three‐step method is demonstrated over the Edvard Grieg field in the North Sea. We can realize this method thanks to advanced seismic multi‐component acquisition via PP and PS seismic data and processing that allows accurate estimation of amplitude‐variation‐with‐offset parameters P‐ and S‐impedances. With time‐lapse P‐ and S‐impedances optimally resolved, we estimate a stable set of axes identifying water saturation increase (water replacing oil), gas saturation increase (gas injection or gas out of solution), pressure increase (at injectors) and pressure decrease (at producers). Once these axes are obtained, we convert every 4D P‐ and S‐impedance data points into 4D pseudo‐saturation and pseudo‐pressure using a transformation of coordinates. We next use the rock physics relationships of this field to show that a linear relationship can be used to map any 4D change in the field from impedances to saturations and pressures. Key locations in the field with largest saturation and pressure changes are used to find calibration values at these extreme points. Next, from the pseudo‐seismic 4D data, a linear mapping is used to calculate actual reservoir property changes (fractions for saturation and bars for pressure). This allows us to obtain fieldwide dynamic values for water and gas saturations and injection and production related pressure changes. The results are shown, and dynamic changes are interpreted on the Edvard Grieg field data. [ABSTRACT FROM AUTHOR]

In quasi-two-dimensional conditions, different invasion patterns can be observed when a fluid displaces another fluid with a higher viscosity. The transition from interfacial instability to fracture during gas invasion remained poorly understood, and classification criteria for different invasion patterns demanded further improvement. In this study, single-point compressed gas injection experiments were conducted in magnesium lithium phyllosilicate (MLPS) suspensions in a rectangular Hele-Shaw cell. Interestingly, with the increase of the injection pressure and the decrease of the concentration of MLPS suspension, the gas invasion pattern underwent a transition from viscous elastic fracture, elastic fracture, elastic viscous fingering to viscous fingering, in which viscous elastic fracture was observed for the first times. We detailly discuss the characteristics and occurrence conditions of each invasion pattern. Furthermore, by analyzing the velocity field of each invasion pattern, it is found that the relationship between the velocity direction around the gas and the gas growth direction varies with different invasion patterns. A simple and effective quantitative indicator is constructed to distinguish the different invasion patterns. Following the identification of invasion patterns, a further investigation was conducted into the relationship between invasion patterns and experimental conditions. By utilizing the relationships among injection conditions and material rheological properties, two dimensionless numbers, Bingham number and Weissenberg number, are conducted, which have an impact on the various invasion patterns and invasion process. A unified phase diagram based on the Bingham number and Weissenberg number was also proposed to incorporate the possible gas invasion patterns in the MLPS suspension. [ABSTRACT FROM AUTHOR]

We studied the electron spin resonance (ESR) spectra of nitrogen atoms stabilized in nitrogen-neon nanoclusters immersed in superfluid 4 He. The nanoclusters were formed during the condensation of the products of the discharge in N 2 –Ne–He gas mixtures into bulk superfluid 4 He at temperature 1.5 K. We studied nanoclusters formed by injection of gas mixtures with different ratios of heavy impurities in the helium N 2 /(Ne + N 2 ) ranging from 2% to 90%. Analysis of the ESR spectra of nitrogen atoms stabilized in nitrogen-neon nanoclusters provides important information about the environment of the stabilized atoms and a shell structure of the nanoclusters was revealed. For all samples studied, preferential stabilization of N atoms on the surfaces of the nanoclusters was observed. Annealing of the collection of the nanoclusters in the temperature range 1.1–10 K resulted in substantial changes in the structure of the nanoclusters. [ABSTRACT FROM AUTHOR]

Carbon geological storage (CGS) is one of the key processes in carbon capture and storage (CCS) technologies, which are used to reduce CO2 emissions and achieve carbon-neutrality and net-zero emissions in developing countries. In Thailand, the Mae Moh basin is a potential site for implementing CGS due to the presence of a structural trap that can seal the CO2 storage formation. However, the cost of CGS projects needs to be subsidized by selling carbon credits in order to reach the project breakeven. Therefore, this paper estimates the economic components of a CGS project in the Mae Moh basin by designing the well completion and operating parameters for CO2 injection. The capital costs and operating costs of the process components were calculated, and the minimum carbon credit cost required to cover the total costs of the CGS project was determined. The results indicate that the designed system proposes an operating gas injection rate of 1.454 MMscf/day, which is equivalent to 29,530 tCO2e per year per well. Additionally, the minimum carbon credit cost was estimated to be USD 70.77 per tCO2e in order to achieve breakeven for the best case CGS project, which was found to be much higher than the current market price of carbon credit in Thailand, at around USD 3.5 per tCO2e. To enhance the economic prospects of this area, it is imperative to promote a policy of improving the cost of carbon credit for CGS projects in Thailand. [ABSTRACT FROM AUTHOR]

Extralow-permeability reservoirs have emerged as a significant area of focus for CO2 geological sequestration due to their stable subterranean structure and expansive storage capacity, offering substantial potential in addressing global climate change. However, the full extent of CO2 geological sequestration potential within these extralow-permeability reservoirs remains largely unexplored. To address this gap, this paper utilizes the Shahejie Formation (Es1 member) of the Shuang 229 block in the Liaohe oilfield, Bohai Bay Basin, as a case study. This section is characterized by its abundant oil-gas reserves and serves as an exemplar for conducting experimental research on CO2 storage within extralow-permeability reservoirs. The results demonstrate that the reservoir lithology of the Es1 member is fine sandstone and siltstone, with high compositional and structural maturity. Moreover, the average porosity is 14.8%, the average permeability is 1.48 mD, and the coefficient of variation of the reservoir is approximately 0.5, which indicates a low- to extralow-permeability homogeneous reservoir. In addition, the overburden pressure is >2.0 MPa, the fault can withstand a maximum gas column height of >200 m, and the reservoir exhibits favorable overburden and fault sealing characteristics. Notably, stepwise increasing gas injection in the Shuang 229-36-62 well reveals that the injected liquid CO2 near the wellhead exhibits a relatively high density, close to 1.0 g/cm3, which gradually decreases to approximately 0.78 g/cm3 near a depth of 2000 m underground. The injected fluid changes into a supercritical state upon entering the formation, and the CO2 injection speed is optimal, at 0.08 HCPV/a. According to these findings, it is predicted that the highest burial CO2 volume via the injection of 1.5 HCPVs in the Wa 128 block area is 1.11 × 105 t/year, and the cumulative burial volume reaches approximately 2.16 × 106 t. This shows that the CO2 sequestration potential of extralow-permeability reservoirs is considerable, providing confidence for similar instances worldwide. [ABSTRACT FROM AUTHOR]

Gas migration behaviour in saturated, compacted bentonite, especially under rigid-boundary conditions, is controversial. Gas breakthrough phenomena, observed under higher pressure gradient conditions in laboratory experiments, are described in literatures by adopting visco-capillary or dilatancy-controlled flow concept. Since, under rigid-boundary conditions, volumetric expansion is restricted and/or water dissipation is not detected, these concepts cannot be implemented satisfactorily. Instead, a diffusion and solubility-controlled (DSC) flow concept was previously found to be adequate for describing the behaviours at lower temperatures (20 °C). The DSC concept describes gas breakthrough as a function of gas solubility. Breakthrough occurs when concentration of dissolved gas reaches or surpasses the solubility limit in the entire specimen. In this work, the DSC flow concept is applied to validate gas migration and breakthrough experiments conducted at higher temperatures, e.g. 40 and 60 °C. Good agreements are observed between the experimental and predicted results, suggesting that the DSC flow concept can be applied to describe gas migration behaviour satisfactorily in rigidly confined saturated bentonites (under constant volume conditions) for various temperature regimes. Results also show that helium dissolution and diffusion processes in saturated bentonite are sensitive to test temperature and pressure conditions. The processes become more stable with increasing gas injection pressure and ambient temperature. [ABSTRACT FROM AUTHOR]

Foam flooding has been successfully implemented in solving problems that arise during gas flooding as it increases gas viscosity and reduces gas relative permeability resulting in favorable mobility ratios and better volumetric sweep efficiency. This research study aims to evaluate the effect of different flood patterns on field performance during foam enhanced oil recovery. A three-dimensional reservoir simulation model was developed with a reservoir simulator and each flood pattern including normal and inverted four, five, seven, and nine-spots were modeled and simulated separately under consistent conditions of field gas injection rate, bottom-hole pressure of production wells, and surfactant concentration. Field Oil Efficiency (FOE), Net Present Value (NPV), Rate of Return (ROR), and Payout Time (POT) were used in making comparisons. An Original Oil in Place of 139.43 MMSTB was found at the initialization. Simulation results showed that a normal and an inverted five-spot pattern were more effective in their respective categories as they resulted respectively in higher FOE, lower FGOR, higher NPV and ROR, and shorter POT. An inverted five-spot resulted in an FOE of 4.36 %, an NPV of $ 83.48 million, and an ROR of 13.64% higher than that obtained for a normal five spot, and a payout time of 1.54 years shorter than that obtained for the normal five spots. The findings highlight the superior efficiency of the normal and inverted five-spot patterns, with the inverted five-spot pattern demonstrating significantly better performance in terms of FOE, NPV, ROR, and POT. Based on the presented results, an inverted five-spot pattern was recommended in this paper as the best flood pattern during foam-enhanced oil recovery applications. [ABSTRACT FROM AUTHOR]

Aiming at the cementing problem of long open hole malignant leakage wells, the thermo-sensitive shape memory loss prevention spacer and foam leakage prevention cement slurry were developed, which synergistically reduce the cementing loss risk of long open hole malignant leakage loss wells. The thermo-sensitive shape memory material was developed, which resistance temperature is 150 ℃ and deformation memory temperature is 80～110 ℃, the length of thermo-sensitive shape memory mesh particles after deformation is 10 times that of normal temperature, and the diameter of shape memory expansion ball after expansion is 3 times that of normal temperature. The thermo-sensitive leak-proof spacer was developed, and the bearing-capacity of 3mm crack can reach 8.5MPa. Foaming agent and foam stabilizer were selected, and foam cement slurry were developed, and the density can be adjusted from 1.12 to 1.31 g/cm3, the difference between the upper and lower parts was less than 0.01 g/cm3, and the compressive strength of 1.12 g/cm3 foamed cement stone can reach 6.6 MPa at 30 ℃/72 h, and bubbles in set cement are uniformly dispersed. The spacer duration design method that considering the equivalent plugging time and washing efficiency was established, and the foamed cement slurry section constant gas injection method was formed. Based on thermo-sensitive anti-leakage spacer and foam cement slurry, The leak-proof cementing technology has been applied for 2 Wells, and the one-time sealing section length exceeds 4000 m, and the spacer and cement slurry returned to the surface successfully and got good results. [ABSTRACT FROM AUTHOR]

To solve the problems of high sampling requirements and low predictive accuracy resulting from the complexity, uniqueness, and randomness of predicting the risk of the CO2 and N2 injection to enhance coal seam gas drainage (CO2/N2–ECGD) technology. The principal component analysis (PCA) method to reduce the dimensionality of the factor data that contribute to the effect risk of the technology was adopted. And the particle swarm optimization (PSO) method was implemented to search for optimal hyperparameters in support vector machine (SVM) by particle search, as a solution to the traditional SVM hyperparameters optimization problem. A novel risk prediction model using machine learning algorithms for gas injection displacement technology was constructed. The prediction results were tested and compared with those of backpropagation (BP), Random Forest (RF), and Decision Tree (DT) models using data from 29 gas injection displacement field projects in China. The results demonstrated that the SVM model had greater accuracy in prediction than the other three models. Additionally, after PSO optimization and dimensionality reduction, the PCA–PSO–SVM model reached 100% prediction accuracy, while requiring less modeling and operation time. The study provided a reliable and reasonable model for predicting technical effects, along with a theoretical basis for risk management and prevention. First, the technology's influencing indicators were analyzed by examining its mechanisms. Second, we utilized the PCA method to reduce the dimensionality of the factor data that contribute to the risk of the technology's effects. Third, we implemented the PSO method to search for optimal hyperparameters in the SVM through particle search, as a solution to the traditional SVM hyperparameters optimization problem. Finally, the prediction results were tested and compared with those of BP, RF, and DT models using data from 29 gas injection displacement field projects in China. The SVM model was found to have greater accuracy in prediction than the other three models. After PSO optimization and dimensionality reduction, the PCA–PSO–SVM model achieved 100% prediction accuracy while requiring less modeling and operation time. The study presents a valid and reasonable model for predicting technical effects and a theoretical basis for risk management and prevention. [ABSTRACT FROM AUTHOR]

Gas condensate reservoirs are generally a mixed system of hydrocarbon and water. This paper is aimed to investigate the phase behavior change influenced by water vapor during the development of depletion and CO2 injection. The Gnorth reservoir of Zhanazhol oilfield in Caspian Basin is taken as an example. Two-phase flash was based on QNSS\Newton method, and multiple contact calculations were performed through cell-to-cell method. The research results indicate that, for the remaining reservoir fluid of depletion development, water vapor has the largest effect on the content change of CH4, followed by C7+, and the smallest effect on C2 to C6. The presence of water vapor makes it easier for the condensate to drop out of the gas phase. For CO2 injection, water vapor is not beneficial to re-evaporation for the formation condensate. Further, the multiple contact miscibility of CO2 and condensate is less affected by water vapor. [ABSTRACT FROM AUTHOR]

Multi-stage fractured horizontal well technology is an effective development method for unconventional reservoirs; however, shale oil reservoirs with ultra-low permeability and micro/nanopore sizes are still not ideal for production and development. Injecting CO2 into the reservoir, after hydraulic fracturing, gas injection flooding often produces a gas channeling phenomenon, which affects the production of shale oil. In comparison, CO2 huff-n-puff development has become a superior method in the development of multi-stage fractured horizontal wells in shale reservoirs. CO2 huff and injection can not only improve shale oil recovery but also store the CO2 generated in industrial production in shale reservoirs, which can reduce greenhouse gas emissions to a certain extent and achieve carbon capture, utilization, and storage (CCUS). In this paper, the critical temperature and critical parameters of fluid in shale reservoirs are corrected by the critical point correction method in this paper, and the influence of reservoir pore radius on fluid phase behavior and shale oil production is analyzed. According to the shale reservoir applied in isolation to the actual state of the reservoir and under the condition of a complex network structure, we described the seepage characteristics of shale oil and gas and CO2 in the reservoir by embedding a discrete fracture technology structure and fracture network, and we established the numerical model of the CO2 huff-n-huff development of multi-stage fractured horizontal wells for shale oil. We used the actual production data of the field for historical fitting to verify the validity of the model. On this basis, CO2 huff-n-puff development under different gas injection rates, huff-n-puff cycles, soaking times, and other factors was simulated; cumulative oil production and CO2 storage were compared; and the influence of each factor on development and storage was analyzed, which provided theoretical basis and specific ideas for the optimization of oilfield development modes and the study of CO2 storage. [ABSTRACT FROM AUTHOR]

Gas condensate reservoirs are generally a mixed system of hydrocarbon and water. This paper is aimed to investigate the phase behavior change influenced by water vapor during the development of depletion and CO2 injection. The Gnorth reservoir of Zhanazhol oilfield in Caspian Basin is taken as an example. Two-phase flash was based on QNSS\Newton method, and multiple contact calculations were performed through cell-to-cell method. The research results indicate that, for the remaining reservoir fluid of depletion development, water vapor has the largest effect on the content change of CH4, followed by C7+, and the smallest effect on C2 to C6. The presence of water vapor makes it easier for the condensate to drop out of the gas phase. For CO2 injection, water vapor is not beneficial to re-evaporation for the formation condensate. Further, the multiple contact miscibility of CO2 and condensate is less affected by water vapor. [ABSTRACT FROM AUTHOR]

The air-booster vacuum preloading method is considered a reasonable choice for alleviating clogging problems. However, research on the air-boost mode during the early consolidation stage is still lacking. In this study, a series of comparative experiments were designed to investigate the effects of applying different pressures and durations on the consolidation characteristics of dredged soil and clogging at two consolidation stages using indoor model tests and microscopic tests. The experimental results showed that the air-boost modes of low pressure and short duration should be adopted during the early consolidation stage, and as the continuous consolidation, the pressure and duration should be increased. Moreover, early gas injection had a more significant effect on alleviating clogging of the prefabricated horizontal drain (PHD), and the pore diameter of dredged soil was also smaller. The research results are an important guide for air-booster vacuum preloading to dewater high-moisture dredged soil. • The implementation of early gas injection is an effective measure in the realm of air-booster vacuum preloading. • Early gas injection can delay the formation time of clogging. • Low pressure and short duration should be used in the early consolidation stage. • This study can provide a new reference for related air-booster vacuum preloading. [ABSTRACT FROM AUTHOR]

Sustainability and longevity of existing gas grid exploitation perspective are closely related to two fundamental issues: their ability to adopt to changing gas fuel production and supply landscape in the context of methane-based fuels, mostly, biomethane, and in the context of non-methane-based fuels, mostly, low carbon and green hydrogen. Renewable gases and their ever-growing presence in gas transmission and distribution systems open up a discussion about the necessity to revise and restructure the original – vertically integrated layout of the gas systems, where gas supply is only technically possible from the transmission system towards distribution one, and not vice versa. Development of numerous decentralized biomethane production facilities connected to the gas distribution system causes a necessity to ensure the possibility to pass biomethane surplus of a certain production area into the gas transmission grid, thus avoiding necessity to install biomethane storage capacities locally and granting other regions an opportunity to use said surplus in their gas consumption immediately. The article addresses biomethane production trends and actions taken towards the development of reverse flow gas stations in France – one of biggest biomethane producers in Europe to date, and opportunities and challenges, which this technique might face in smaller and less active renewable gas markets as the one of Latvia. [ABSTRACT FROM AUTHOR]

Conventional recovery enhancement techniques are aimed at reducing the abandonment pressure, but there is an upper limit for recovery enhancement due to the energy limitation of reservoirs. Gas injection for energy supplementation has become an effective way to enhance gas recovery by reducing hydrocarbon saturation in gas reservoirs. This review systematically investigates progress in gas injection for enhanced gas recovery in three aspects: experiments, numerical simulations and field examples. It summarizes and analyzes the current research results on gas injection for EGR and explores further prospects for future research. The research results show the following: (1) Based on the differences in the physical properties of CO2, N2 and natural gas, effective cushion gas can be formed in bottom reservoirs after gas injection to achieve the effects of pressurization, energy replenishment and gravity differentiation water resistance. However, further experimental evaluation is needed for the degree of increase in penetration ability. (2) It is more beneficial to inject N2 before CO2 or the mixture of N2 and CO2 in terms of EGR effect and cost. (3) According to numerical simulation studies, water drive and condensate gas reservoirs exhibit significant recovery effects, while CO2-EGR in depleted gas reservoirs is more advantageous for burial and storage; current numerical simulations only focus on mobility mass and saturation changes and lack a mixed-phase percolation model, which leads to insufficient analysis of injection strategies and a lack of distinction among different gas extraction effects. Therefore, a mixed-phase-driven percolation model that can characterize the fluid flow path is worth studying in depth. (4) The De Wijk and Budafa Szinfelleti projects have shown that gas injection into water drive and depleted reservoirs has a large advantage for EGR, as it can enhance recovery by more than 10%. More experiments, simulation studies and demonstration projects are needed to promote the development of gas injection technology for enhanced recovery in the future. [ABSTRACT FROM AUTHOR]