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The coalescence of two growing bubbles presents unique characteristics compared to static bubble coalescence. The gas injection flowrate significantly affects the different stages of bubble evolution, which is poorly understood. In this study, we investigate the flowrate effects on the lateral coalescence of two growing bubbles experimentally. The synchronous bubbling from adjacent needles is achieved using water to push air. During the bubble growth process, we find that the initial nonlinear evolution of bubble volume is because the bubble emerges as a small spherical cap with a large curvature radius and apparent contact angle. As the neck expands after bubble coalescence, the injection flowrate accelerates the neck evolution compared to the case without air injection. We find the neck expansion time decreases linearly with increasing flowrate, while the expansion speed increases with flowrate, but only in the early stage. Moreover, we propose a new theoretical expression that predicts the neck radius well at all the flowrates. At the post‐coalescence oscillation stage, the average projection area of the coalesced bubble increases linearly with time, except for periodic oscillations. Besides, we find that the injected air primarily influences the coalesced bubble's height, which in turn affects the projection area. [ABSTRACT FROM AUTHOR]

Ozone injection is an effective way to oxidate Hg0 in flue gas. The reacting flow field for the oxidation of Hg0 by O3 is numerically studied in detail with a reduced chemical mechanism in this paper. Based on sensitivity analysis with detailed chemical mechanism, a 12-steps reduced chemical mechanism is obtained and used in the following three-dimensional simulations of the reacting flow field. Through the reacting flow field simulation, the influence of various factors on Hg0 oxidation efficiency is calculated and analyzed, such as O3/NO molar ratios, jet velocities, moisture, temperatures, NO concentrations and Hg0 concentrations. Results show that temperature and O3/NO molar ratio are the key factors, jet velocity and NO concentration are the important factors, while water content has little effect. It is also found that the oxidation efficiency of Hg0 is shown to be highly correlated with the amount of NO3 generated in the flue gas. Increasing the local generation of NO3 may be the key to achieve efficient oxidation of Hg0. This study is good help of subsequent engineering applications. [ABSTRACT FROM AUTHOR]

Pre-cooled engines, in which the incoming air is cooled by a pre-cooler before it enters the subsequent components for operation, are one of the important developments in combined power solutions. Therefore, how to optimize the gas temperature uniformity of the high temperature gas stream at the outlet of the pre-combustion chamber to achieve higher efficiency of the pre-cooled engine will be the main research content. In this paper, grid partitioning was performed on the pre combustion chamber model, and the k-omega model and EDC model were used to simulate the internal flow field of the pre combustion chamber. And verify the correctness of the simulation through engine hot testing. Explored the changing trends of the internal velocity and temperature fields of the engine under different secondary injection structures. The larger the secondary injection flow rate, the more obvious the obstruction to high-temperature gas, and the better the uniformity of gas temperature. However, in experiments, the secondary injection components often cannot withstand a large flow rate ratio. Ultimately, the gas temperature uniformity is best when the secondary injection flow rate ratio is 65%. Circumferential deflection will cause the gas to spin, and the spinning process will make the gas temperature at the same radius more uniform. However, due to the decrease in radial velocity, the obstruction effect on the overall high-temperature gas is weakened. When the gas is deflected towards the head by 30°, the velocity of the incoming gas and the velocity of the secondary injection gas are combined and perpendicular to the axis. At this time, the gas temperature uniformity is the best. [ABSTRACT FROM AUTHOR]

The development of shale oil often encounters a series of challenges, such as insufficient natural energy, rapid declines in production, and low oil recovery. Given its wide availability and low cost, natural gas serves as an ideal injection medium to enhance shale oil recovery. Based on the foundational data from Chang 7 block X in the Ordos Basin and considering the influence of reservoir stress sensitivity, this study uses numerical simulation methods in conjunction with the random forest algorithm to examine gas flooding in shale oil. This research aims to identify the key factors influencing the effectiveness of natural gas flooding for shale oil and to establish a chart for the adaptive natural gas flooding development boundary. The findings suggest that, for reservoirs with permeability less than 0.2 × 10−3 μm2 and oil saturation below 55%, it is advisable to adopt longer fracture lengths during hydraulic fracturing to achieve better development results. After 10 years of gas flooding, continuing the use of this method is not recommended, and adjusting of the development strategy becomes essential. For extended development periods, avoiding long-length fractures is crucial to mitigate gas channeling and ensure the effectiveness of the development process. This study offers theoretical guidance and technical support for developing shale reservoirs with natural gas flooding. [ABSTRACT FROM AUTHOR]

Fault slip induced by gas injection and extraction cycles in underground gas storage (UGS) sites have been reported in many countries. Knowledges of the contemporary in situ stress condition and its evolution with gas injection and extraction cycles are crucial to estimate the fault-slip tendency ( T s ). Using the Wx-1 UGS reservoir in the Turpan Basin (China) as an example, we studied the evolution of the stress state and fault-slip tendency associated with the injection and extraction cycles. To assess the minimum horizontal stress (Shmin) in the storage reservoir and its caprock, we conduct flowback-assisted minifrac tests to measure the magnitudes. The magnitudes of maximum horizontal stress (Shmax) were estimated and constrained by multiple sources. The 3D in situ stress field was constructed by the finite-element method (FEM), constrained by field stress measurements. Using coupled reservoir–geomechanical simulations, we estimated the changes in stress state over time and the tendency for fault slip in response to gas injection and extraction. The results showed that (1) the in situ stress state at Wx-1 UGS field is a strike-slip (SS) faulting stress state; (2) for fault-slip analysis, decoupled analysis considering only the pore pressure-induced fault slip can overestimate the pore pressure needed to cause the fault slip ( P sf ), while coupled analysis using a poroelastic FEM formulation considers both pore pressure and injection-induced shear stress changes and can provide more reasonable estimates of P sf ; (3) both the mean effective stresses ( p ′ ) and shear stresses (τ ) changes with the injection and extraction cycles; (4) the fault-slip tendency increases continuously with gas injection and decreases with gas extraction; (5) the faults striking at low angles with respect to the orientation of Shmax are critically stressed in the contemporary in situ stress field, and the possibility of injection-induced fault slippage is the controlling factor of the maximum operation pressure (MOP) of this UGS site. Highlights: Flowback-assisted minifrac tests were conducted in the low-permeability caprock formations to measure the in situ stress conditions efficiently. 3D in situ stress field was constructed by FEM simulations and constrained by minifrac tests. Coupled reservoir–geomechanics simulations were used to investigate the in situ stress evolution with gas injection and production cycles and to analyze the fault-slip tendency. The slip tendency undergoes temporal changes due to the fluctuation of both shear stress and mean effective stress during injection and extraction cycles. The maximum operation pressure (MOP) of this UGS site is determined by the likelihood of fault slippage caused by injection. [ABSTRACT FROM AUTHOR]

The authors have presented a theoretical model of the process of hydrate formation in a porous medium on injection of gas into it in the case where the hydrate-formation kinetics is described by the Arrhenius law. It has been established that in the case of a phase-transition boundary impermeable to the gas flow hydrate formation is implemented mainly at constant pressure. It has been shown that on injection of the gas with a temperature equal to the initial temperature in the stratum, the entire water in its pores goes into a gas-hydrate state. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effectiveness and safety of adjustable and free postoperative positioning after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD).Design: Prospective, randomized controlled study.Methods: A total of 94 eyes with RRD were enrolled from April 2020 to April 2023 and monitored postoperatively for at least 3 months. All patients underwent PPV combined with silicone oil injection or gas tamponade and were randomly divided postoperatively into two groups: an adjustable positioning group and a free positioning group. The success of the outcome was based on the retinal reattachment rate, best corrected visual acuity (BCVA), postoperative complications, and ocular biometric parameters such as anterior chamber depth (ACD) and lens thickness (LT).Results: The initial retinal reattachment rate was 97.9% in the adjustable positioning group and 95.7% in the free positioning group, manifesting no statistical difference between the two groups. Similarly, no statistical difference was observed between the two groups in the final BCVA, which was significantly improved compared to the preoperative BCVA. The comparison of the 1-month postoperative ACD and LT with the preoperative values showed no statistically significant differences in the two groups. The rates of complications were not statistically different in the two groups.Conclusion: After treating RRD using PPV, neither the adjustable nor the free postoperative positioning affected the retinal reattachment rate or the incidence of complications. Therefore, our study showed that it is safe and effective to adopt free positioning postoperatively, which may provide more options for patients with RRD undergoing PPV. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies of the formation of reactive oxygen and nitrogen species in Milli-Q® deionized water (electrical conductivity of ≤0.1 µS/cm) under the influence of a multi-spark pulse discharge with gas injection into the interelectrode space. The discharge is a set of microplasma formations in a multiphase medium, for which the specific energy input is estimated. The influence of injected gases (argon, air) on the formation of a plasma discharge in the interelectrode space and long-lived chemical compounds: hydrogen peroxide, nitrite ions and nitrate ions is analyzed. The variation of the exposure duration to water from 2 to 10 min leads to a change in its chemical composition and electrical conductivity properties, but has virtually no effect on the characteristics and duration of the breakdown stage of the discharge. At the same time, changes in the concentrations of hydrogen peroxide, nitrite ions and nitrate ions are recorded within 1 h after the termination of the plasma exposure. Sputtering of stainless steel electrodes is detected, which is about 1 mg/min and leads in some cases to the formation of an insoluble precipitate. The data obtained allow the optimization of the effect of plasma-activated liquid on plants and planting material. [ABSTRACT FROM AUTHOR]

In this work, a new micro-electrode bubble generator is presented that employs a micro-electrode installed inside a small nozzle enabling the production of bubbles with controllable size and frequency. This bubble generator can be employed as a simple and potentially cheap method for the generation of single bubbles in a liquid, as long as it enables ion exchange, as an alternative to more complicated methods such as timely injection of a gas through a nozzle, which requires sophisticated nozzle design, manufacturing, and monitoring of the injected gas flow rate. A systematic investigation was conducted to assess the effect of the bubble generator dimensions, applied voltage, and electrolyte flow conditions on the size and frequency of the generated bubbles. It was shown that when the micro-electrode is thinly concealed within the nozzle, this bubble generator can successfully produce bubbles covering a wide range of diameters from 0.4 to 1.4 mm with a size distribution standard deviation of about 25%. The mechanism of single and continuous bubbles formation from the proposed bubble generator is also discussed. While this paper introduces this new micro-electrode bubble generator, further work is required to optimize it, enabling more accurate control over bubble size and frequency. [ABSTRACT FROM AUTHOR]

The conventional liquid acid has several shortcomings in the acidizing process of fractured-vuggy carbonate reservoirs, including high filtration loss, fast reaction rate, high friction resistance, and difficult flowback. To address these issues, a new atomizing acid acidizing technology is proposed, combining the gas injection development practice from the fractured-vuggy carbonate reservoir in the Tahe oilfield. The laboratory experiments were conducted to optimize the type and concentration of atomized acid, iron ion stabilizer, corrosion inhibitor, and atomization stabilizer. The acid atomization rate was evaluated under different combinations of gas and liquid injection flows using a self-made atomized acid well migration simulator, and the best atomization scheme was selected. Furthermore, a kinetic experiment for the acid–rock reaction was carried out to evaluate the retarding performance of the atomized acid. The optimized formula for the atomizing acid system consists of 15~25% hydrochloric acid, 0.005% atomizing stabilizer (AEO-7), 1% iron ion stabilizer (EET), 1.5% corrosion inhibitor (EEH-160), and water. The optimal gas and acid injection scheme is gas injection at 2m3/min and acid injection at 10 mL/min, which maintains an atomization rate of over 80% after the acid mist migrates through the wellbore. Compared with gelling acid, the acid–rock reaction rate of atomized acid is 8.5, 9.1, and 10.6 times slower under acid concentrations of 15%, 20%, and 25% respectively. The retarding effect of atomized acid is superior, facilitating etching and initiating underdeveloped gas drive channels and thereby increasing the probability of gas communication with new reservoirs. The research findings presented in this paper establish a theoretical foundation for the practical implementation of the atomized acid acidizing process in the field. [ABSTRACT FROM AUTHOR]

Batch experiments were conducted to collect data for obtaining insights into the chemical mechanisms and kinetics of red mud neutralization by both atmospheric (passive treatment) and injected CO2 (active treatment) in the absence and presence of gypsum. Active treatments allowed effective sequestration of CO2 within 1 h. A mixing ratio of gypsum to red mud at 0.04–0.06 enabled effective control of pH rebound, completely eliminating the causticity of the red mud by reducing the pH value of red mud to < 9. The carbonation of red mud was realized through the formation of carbon-containing minerals, mainly basic aluminium carbonates (largely dawsonite), sodium bicarbonate, sodium carbonate and calcite. The importance of calcite as a carbon carrier increased when gypsum was added. Passive treatments also allowed simultaneous causticity reduction and carbon sequestration but at a much slower rate compared to the active treatments. The research findings obtained from this study have implications for developing strategies to cost-effectively manage red mud. Where flue gas is available, active treatment could be a feasible option for simultaneously reducing the harmfulness of red mud and CO2 emission. Passive treatment can be used as a natural attenuation process for low-cost management of red mud. Where off-site utilization of red mud is feasible, gypsum addition at an optimal rate could be a more appropriate option. For future study, industrial-scale experiments are required to validate the research findings obtained from this laboratory-scale study. Highlights: • Injection of CO2 into red mud slurry with added gypsum allowed simultaneous causticity reduction and carbon capturing. • Passive treatment by exposing red mud slurry to atmospheric air had the same effects but at a much slower rate. • Carbon sequestration was via formation of dawsonite, sodium (bi)carbonate and calcite, which were stable upon aging. [ABSTRACT FROM AUTHOR]

As a response to stricter exhaust emission regulations, an increasing number of diesel-powered ships are switching to liquefied natural gas (LNG) fuel or installing post-processing devices to reduce exhaust gas. However, these methods are not feasible for small ships operating primarily along the coast. This is because the cost of the exhaust gas post-processing devices is high, while a large-volume fuel system is required in the case of LNG. Thus, this study used a propane gas fuel system based on a 5.0 L gasoline engine for easy application to existing small ships without major modifications. To optimize the control according to changes in the fuel system, a 1D simulation was performed on the engine to be developed, and ignition timing optimization was investigated. In addition, fuel consumption was compared with that of a gasoline-based engine. The propane engine achieved over 95% power in comparison to a gasoline-based engine. During cold-start tests, starting performance at −15 °C was ensured. The purpose of this study is to provide guidelines to assist the development of LPG or propane engines based on gasoline engines through these processes. [ABSTRACT FROM AUTHOR]

Plant hydraulic traits related to leaf drought tolerance, like the water potential at turgor loss point (TLP) and the water potential inducing 50% loss of hydraulic conductance (P 50), are extremely useful to predict the potential impacts of drought on plants. While novel techniques have allowed the inclusion of TLP in studies targeting a large group of species, fast and reliable protocols to measure leaf P 50 are still lacking. Recently, the optical method coupled with the gas injection (GI) technique has been proposed as a possibility to speed up the P 50 estimation. Here, we present a comparison of leaf optical vulnerability curves (OVcs) measured in three woody species, namely Acer campestre (Ac), Ostrya carpinifolia (Oc) and Populus nigra (Pn), based on bench dehydration (BD) or GI of detached branches. For Pn, we also compared optical data with direct micro-computed tomography (micro-CT) imaging in both intact saplings and cut shoots subjected to BD. Based on the BD procedure, Ac, Oc and Pn had P 50 values of −2.87, −2.47 and −2.11 MPa, respectively, while the GI procedure overestimated the leaf vulnerability (−2.68, −2.04 and −1.54 MPa for Ac, Oc and Pn, respectively). The overestimation was higher for Oc and Pn than for Ac, likely reflecting the species-specific vessel lengths. According to micro-CT observations performed on Pn, the leaf midrib showed none or very few embolized conduits at −1.2 MPa, consistent with the OVcs obtained with the BD procedure but at odds with that derived on the basis of GI. Overall, our data suggest that coupling the optical method with GI might not be a reliable technique to quantify leaf hydraulic vulnerability since it could be affected by the 'open-vessel' artifact. Accurate detection of xylem embolism in the leaf vein network should be based on BD, preferably of intact up-rooted plants. [ABSTRACT FROM AUTHOR]

The development of renewable and low‐carbon gases for injection into the gas grid obtained by different processes such as anaerobic digestion, pyrogasification, hydrothermal gasification, and methanation, followed by upgrading steps, increases the demand for analysis and characterization in order to fully manage their integration into the gas value chain. If the analysis of the main compounds (methane, carbon dioxide, hydrogen, and carbon monoxide) is well described, the analysis of impurities in renewable gases remains more challenging due to their various natures and quantities. After a brief description of renewable and low‐carbon methane production processes, the review focuses on the methods used for the analysis of the different compounds in renewable gases, from the main ones to impurities at ppbv levels. Gas chromatography (GC), coupled with different detectors, is the preferred technique, enabling the analysis and quantification of siloxanes, terpenes, oxygenates, and sulfur compounds. Recently, comprehensive two‐dimensional GC has been applied to renewable gases, increasing the number of compounds detected. Non‐chromatographic techniques are also reviewed. As sampling is of major importance in the search for reliable analyses, a whole section is devoted to this aspect. Among the available methods, pre‐concentration on adsorbent tubes emerges as the most relevant solution. [ABSTRACT FROM AUTHOR]

Gas Assisted Gravity Drainage (GAGD) process is an immiscible gas injection Improved Oil Recovery (IOR) technique that is designed to take advantage of gravity force that allow vertical segregation between injected gas and reservoir crude oil. This segregation is due to the density difference between oil and gas. The GAGD process uses vertical injection wells at the top of the reservoir, and horizontal production wells near the bottom of the pay zone. This method is preferable than the traditional gas injection process because it provides better sweep efficiency and utilizes the gravity force. In this study, the effects of several reservoir/design parameters on the performance of GAGD process are investigated using numerical reservoir simulation means. These factors include reservoir dimension, oil viscosity, reservoir permeability, and well coordination. The results show that the investigated parameters have various degrees of influence on the performance of GAGD process. [ABSTRACT FROM AUTHOR]

Conventional methods for producing porous metals involve the use of chemicals such as thickeners and foaming agents under high temperatures and pressures. However, these methods are costly and pose a risk of dust explosion. Thus, the objective of this research is to achieve the cost-effective and safe production of porous metals by introducing microbubbles generated by ultrasonic oscillation into the molten metal. One end of an ultrasonic horn was inserted into three different molten metals—white metal, Pb-free solder, and zinc—and microbubbles were generated at the horn end by the strong ultrasonic oscillation in the molten metals. The microbubbles that contained molten metal changed phase to porous metal through solidification, and the diameter, porosity, and stress–strain curve of the generated porous metals were measured. The results indicate that the porosity of white metal, Pb-free solder, and zinc foams reached 54%, 76%, and 48%, respectively, and these porous metals had many micropores less than 1 mm in diameter. It was also observed that the higher the melting point, the larger the pore diameter and the lower the porosity. Furthermore, in the case of white metal, a plateau region of large deformation at constant stress was observed in the stress–strain curve. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Acid gas injection operations function as the commercial equivalent of certain aspects within the realm of geological CO2 storage. Acid gas, composed of H2S and CO2, alongside minor quantities of hydrocarbon gases stemming from either petroleum production or processing, constitute the composition of acid gas. The primary aim of acid gas injection operations lies in the disposal of H2S. Nevertheless, substantial volumes of CO2 are concurrently injected due to the economic impracticality of segregating the two gases. This investigation delves into the comprehensive, step-by-step procedure that can be employed to determine the suitability of a field or formation for acid gas injection, utilizing all accessible data, including the literature and data from neighboring fields. This approach incorporates sensitivity analysis of various parameters to ascertain the feasibility of AGI while minimizing costs and time consumption. The focus of this study centers on evaluating the feasibility of Acid Gas Injection (AGI) in a saline aquifer offshore in Iran. The assessment encompasses the examination of reservoir properties, geomechanical aspects, caprock integrity, and gas plume dynamics. The Surmeh formation emerges as a promising candidate for AGI due to the presence of upper dolomite and lower carbonate within the rock formations. Geomechanical analysis reveals a pore pressure of 3800 psi and a fracture pressure of 6100 psi. Caprock integrity, particularly within the Hith formation, emerges as pivotal for both containment and long-term stability. Seismic mapping highlights variations in caprock thickness, influencing containment effectiveness. Capillary trapping emerges as a significant factor in short-term gas entrapment and plume distribution. Numerical simulations elucidate the impact of heterogeneous rock properties on capillary trapping and gas plume movement. The projection estimates approximately 2 TCF (Trillion Cubic Feet) of acid gas injection into the Surmeh formation. Based on the acid gas content and the gas in place at the source of injection, the recommended injection rate stands at 180 MMSCFD (million standard cubic feet per day). The formation's inherent tightness limits injectivity, allowing for a maximum achievable rate of 7 MMSCFD with a permeability of 1 mD (millidarcy). However, a higher porosity (12%) and a permeability of 100 mD enable more efficient injection without fracturing the formation. To achieve this, it becomes imperative to implement two injection wells, each with a capacity of 90 MMSCFD. [ABSTRACT FROM AUTHOR]

Water alternating gas (WAG) is a cyclical process that involves alternating water and gas injections with the primary goal to improve sweep efficiency by maintaining initial high pressure, slowing water and gas breakthrough, and lowering oil viscosity. The objective of this work is to apply and optimize a WAG strategy on a carbonate field with light oil, compare it to the initially planned water-flooding strategy, and investigate the capability of WAG to improve field production. In this research, a compositional reservoir simulator was used to model a WAG process by injecting produced gas into the reservoir, using the same well structure as an optimized water-flooding strategy. Subsequently, a WAG strategy was created, optimizing the number and locations of wells, to facilitate a comparative analysis of the two recovery methods. The WAG optimization involved a detailed assessment of variables such as bottom hole pressure (BHP), WAG cycle duration, maximum gas oil ratio (GOR), and well positioning, to achieve a high net present value (NPV). The study focuses on the application of WAG optimization modeling in unconventional reservoirs, specifically pre-salt carbonate reservoirs, and investigates its implications on production strategy and forecast, emphasizing its potential for maximizing NPV and oil recovery in a recently producing field. The results showed that WAG improved reservoir performance when compared to water injection and produced a greater amount of oil. This solution showed potential to be tested under uncertainties (reservoir heterogeneity, faults, fractures, karsts, vugs, etc.) as future steps. [ABSTRACT FROM AUTHOR]

Gas injection structures were designed for a vertical oven to improve the gas–solid flow countercurrent structure. This work measured the wall temperature distribution of the vertical oven to reflect gas velocity distribution, and simulated the basic gas–solid flow field. The effects of the number of gas orifice layers and the injection angle on the gas velocity distribution were examined. The results showed that number of gas injection layers had a significant effect on the gas velocity distribution in the lower zone. Compared with the distributions with one or three injection layers, two injection layers produce more uniform gas flow. A small particle size of 6–15 mm increased the bed resistance and solid fraction standard deviation. A nozzle angle of 45° was conducive to increase the gas velocity in the upper zone and forming a more uniform gas distribution. [ABSTRACT FROM AUTHOR]

Abstract It is necessary to improve oil production from reservoirs. Various methods have been proposed to increase oil extraction from reservoir. Each method has specific challenges. In this research, the effect of water and gas injection in to Azadegan reservoir has been analyzed. Azadegan oil field is located south of Iran. In this study, water, immiscible gas and water alternating gas injected to reservoir and its effect on enhanced oil recovery have been investigated. Finally, a comparison between results of methods is provided. Results show that effective method for enhanced oil recovery is immiscible gas injection with 46% oil production efficiency and water alternating gas injection with 36% oil production efficiency. This study shows that oil production efficiency can be increased if duration of gas injection is increased. This study shows, increasing viscosity of water in water alternating gas scenario did not improve the production of Azadegan reservoir.

Injection of natural/associated gas is widely used as an efficient method of enhanced oil recovery in carbonate oil reservoirs in both miscible and immiscible conditions. Due to reservoir oil compositional changes by injected gas, asphaltenes instability may occur. In spite of the broad reported studies on gas injection process, the effect of miscible gas injection phenomenon on asphaltenes precipitation and deposition at reservoir conditions has not been well attended. The aim of this study is to recognize the effect of miscible and immiscible injection of natural gas on the asphaltenes deposition, permeability alteration and oil recovery. Additionally, the impact of different live and recombined oil samples on asphaltenes instability is investigated. Permeability alteration by the formation of asphaltenes is analyzed through the permeability measurements before and after gas flooding. Permeability reduction is found to be function of miscibility state, injection pressure and type of oil samples. It is observed that experiments conducted with live oil and at lower injection pressures show more permeability reduction. It is assumed an additional oil recovery associated with fluid path diversion caused by asphaltenes deposition in miscible and immiscible conditions. The miscible gas flooding causes the lower asphaltenes deposition and lower recovery enhancement. These effects are due to the fluid path diversion, nevertheless, miscible natural gas injection has high potential of oil recovery. Due to miscible bank development, the composite core along with higher injection pressure respect to minimum miscibility pressure shows higher recovery in comparison to the short core sample.

Mixing in a reactor can be achieved mechanically or by the injection of a gas. This can be done by injecting a gas towards the bottom of the tank. The induced flow recirculation and then the stirring quality depends on the bubbles morphology, rising velocity and frequency detachment. This study focus on the case where the stirred fluid exhibits a yield stress. It is in line with previous studies on the gas cavity at the injection point [1], the induced flow recirculation [2] and the numerical simulation [3]. Here we quantified the bubbles diameters, aspect ratios and velocities as a function of the air flow rate, rheological parameters and tank size. Scaling laws and correlations based on the characteristic dimensionless numbers governing the flow have been proposed and validated experimentally. It was found that bubble frequencies and consequently bubble volumes and velocities are mainly governed by the balance between inertial and buoyancy forces. However, viscous and yield stress effects play an important role along buoyancy and inertial in defining the bubble aspect ratios. Weakly inertial flows are characterized by elongated bubbles while high inertial flows produce almost spherical bubbles. These experimental results are of practical interest for the design of reactor or digester where yield stress fluids have to be stirred.

This work contributes to study the particle projection mechanism during gas injection on a molten steel bath surface. The studied element is called "dome". It results from a cluster of particles which is propelled and molded onto the vault of the VOD installation. A bibliographical analysis of previous projection studies leads toward two main topics: an analytic model to characterize the collected projections and a chemical analysis to trace the emission droplets. The main result leads to observe that the predicted droplet size and dome quantity go hand in hand with results obtained experimentally for the studied casting. Indeed, based on semi-empirical equations in literature, an analytical model predicts an average propelled particle size of about 500 μm with a dome mass of one-Ton. Furthermore, the metallographic analysis of some samples highlight a crystallization of seeds linked each other and, the presence of spherical droplets size between 100 and 800 µm. [ABSTRACT FROM AUTHOR]

Numerous reservoirs that play a significant role in worldwide petroleum production and reserves contain fractures. Typically, the fractures must form a connected network for a reservoir to be classified as naturally fractured. Characterizing the reservoir with a focus on its fracture network is crucial for modeling and predicting production performance. To simplify the solution, dual-continuum modeling techniques are commonly employed. However, to use continuum-scale approaches, properties such as the average aperture, permeability, and matrix fracture interaction parameters must be assigned, making it necessary to improve the fracture depiction and modeling methods. This study investigated a fractured reservoir with a low matrix permeability and a well-connected fracture network. The focus was on the impact of the hierarchical fracture network on the production performance of gas-based enhanced oil recovery methods. The discrete fracture network (DFN) model was utilized to create comprehensive two-dimensional models for three processes: gas injection (GI), water alternating gas (WAG), and foam-assisted water alternating gas (FAWAG). Moreover, dimensionless numbers were employed to establish connections between properties across the entire fracture hierarchy, spanning from minor to major fractures and encompassing the fracture intensity. The results indicate that the FAWAG process was more sensitive to fracture types and networks than the WAG and GI processes. Hence, the sensitivity of the individual EOR method to the fracture network requires a respective depth of description of the fracture network. However, other factors, such as reservoir fluid properties and fracture properties, might influence the recovery when the minor fracture networks are excluded. This study determined that among the enhanced oil recovery (EOR) techniques examined, the significance of the hierarchical depth of fracture networks diminished as the ratio of major (primary fracture) aperture to the aperture of medium and minor fractures increased. Additionally, the impact of the assisted-gravity drainage method was greater with increased reservoir height; however, as the intensity ratio increased, the relative importance of the medium and minor fracture networks decreased. [ABSTRACT FROM AUTHOR]

Gas cap blow down strategy is normally deployed for Ultra-thin oil rim reservoirs with huge gas caps due to extremely high gas oil ratios from wells in such reservoirs. The current state leads to loss of production from the oil reserves due to high initial reservoir pressure thus, reducing its net present value. Data on important factors essential to the productivity of oil rim reservoirs are used to build a heterogeneous ultra-thin reservoir with a time step of 10,000 days using the Eclipse software and its embedded correlations. The reservoir is subjected to a gas cap blowdown via a gas well, then an oil well is initiated into the model at onset and after time periods of 2000 days, 4000 days, 6000 days and 8000 days to estimate the oil recovery. It is expected that due to the large nature of the gas cap, pressure decline will be drastic and leading to a low oil recovery, hence the injection of water and gas at different rates at the periods indicated. The results indicate an oil recovery of 4.3% during gas cap blow down and 10.34% at 6000 days. Peak oil recoveries of 12.64% and 10.80% are estimated under 30,000 Mscf/day at 4000 days and 1000 stb/day at 6000 days respectively. This shows an incremental oil recovery of 8.34% and 6.5% over that recorded during gas cap blow down. The results also indicate that the gas production at those periods was not greatly affected with an estimated increment of 257 Bscf recorded during 30,000 Mscf/day at 4000 days. All secondary injection schemes at the respective time steps had positive impact on the overall oil recoveries. It is recommended that extra production and injection wells be drilled, enhanced oil recovery options and injection patterns be considered to further increase oil recovery. [ABSTRACT FROM AUTHOR]

Yaha condensate gas reservoir is condensate gas reservoir developed by gas injection in the Tarim Basin. The practice of gas injection in condensate gas reservoir shows that the key to improve gas injection effect is to control gas channeling. Dynamic monitoring shows that there is no instantaneous miscibility between dry gas and condensate gas during gas injection. Based on the principle of entropy increase and mass transfer kinetics, the phase behavior of condensate gas and dry gas in reservoir is analyzed theoretically. The new technique to improve condensate recovery is adopted for condensate gas field. By using the density difference and seepage characteristics of dry gas and condensate gas, the injected dry gas cap is formed at the top of the gas reservoir, and the three-dimensional displacement is realized by the expansion of dry gas cap. Gas injection gravity assisted flooding technology is to realize vertical displacement of injected gas through the expansion of dry gas cap by using gravity differentiation caused by gas density difference. This technology can keep the front edge of gas injection advance evenly and solve the problem of gas channeling in the process of cyclic gas injection. [ABSTRACT FROM AUTHOR]

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At present, there is a common problem that the mixing mode is single and it is difficult to overcome the inherent bottleneck of multiphase mixing. A mixing device combining the advantages of jet entrainment and mixing dispersion was designed and built. In an effort to determine the mixing degree of two phases, the mixing coefficient of gas–liquid charging was measured using the cylinder method with the optimal working parameters. To explore the optimization of the mixing conditions and control mechanism of multiphase materials, the law of gas–liquid shear mixing in the process of multi-force field synergistic change was revealed. Based on the testing of the gas injection capacity under different working conditions and the calculation of the gas–liquid two-phase mixing coefficient, it was concluded that the flow rate was the direct key factor affecting the gas injection capacity. The working speed also had a certain impact on the gas injection capacity. When working at a high speed and high flow rate, the jet beam broke through the cutting barrier and presented a superposition effect. The jet impact assisted the rotation, and the suction performance of the device was significantly improved, which was conducive to the mixing of the gas and liquid phases. According to the test results of the measuring cylinder method, the calculated average inflation volume is 0.01 m 3 / (m 2 · m i n) , the inflation uniformity coefficient is 77.51, and the mixing coefficient of the gas and liquid phases is 0.12. [ABSTRACT FROM AUTHOR]

Water-based enhanced oil recovery methods have been developed to improve the oil production rate from ultra-tight reservoirs. By coupling the effect of surfactant as wettability alteration and water alternating gas injection method, we aimed to determine the most efficient enhanced oil recovery technique. We performed seven injectivity scenarios to measure the oil recovery factor by introducing the alkylbenzene sulfonic acid (LABSA) as a surfactant agent during the active carbonated water alternating gas (ACWAG) injection. To consider the effect of slug size during water alternating gas injection, we used two different slug sizes (0.3, and 0.6). After the water breakthrough, a little oil volume was produced, and the maximum oil recovery factor at 1.5 Pore Volume (PV) was 26%. This issue corresponded to the water channeling after the breakthrough point. For smaller slug sizes (0.3), the maximum oil recovery factor (78%) was reached in smaller pore volumes. One of the exciting results wass the considerable influence of slug ratio during the water alternating gas (WAG) injection, in which it provided more oil recovery factor (83%) when the gas volume is higher than the water volume. Finally, by introducing the coupling effect of active carbonated water (made by LABSA surfactant) and WAG injection, the maximum oil recovery factor was 85%, corresponding to the better efficiency of active carbonated water in interfacial tension reduction. The results of this comprehensive investigation can be extended in ultra-tight sandstone reservoirs and can be applied as a further guideline in numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, a theoretical model for simulation of a solar updraft tower power plant with the assumption of axisymmetric condition is developed to study the impact of hot gas injection at the chimney base as well as extraction of a portion of hot gas after the turbine and re-entered it at the collector inlet. A new computational code is written by Matlab software and the effects of operational parameters are studied. Results show that the maximum power output is increased by 49.9% by increasing the extraction fraction from 0% to 40% at a wind velocity of 10 m/s. Besides, the obtained results show that the power output is enhanced as the mass flow rate of hot gas increases. As a result, the maximum power output at a hot gas mass flow rate of 30 kg/s is approximately 37% higher than the one at a hot gas mass flow rate of 10 kg/s. Results reveal that the optimum performance of SUTPP takes place at the ratio of pressure drop across the turbine to driving pressure potential in the range from 0.83 to 0.87. Furthermore, the power output in the presence of wind is investigated and the positive influence of wind is illustrated. Results indicate that by increasing the wind velocity from 10 m/s to 30 m/s, the maximum power output is increased by 386.1% [ABSTRACT FROM AUTHOR]

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CO2 displacement is a common technique for the enhanced oil recovery and simultaneously alleviates the greenhouse effect. However, the recent applications of CO2 displacement focus on the formations where the fluid and reservoir properties could not reach absolute miscibility. The reactions between CO2 and high pour point crude oil during the near-miscible displacement process would be far more complex. In this study, slim-tube and one-dimensional core (sand-filling model, splicing long core) displacement experiments were carried out. Group component analysis and saturated hydrocarbon analysis were applied during the process and the possibility of organic solid deposition and blockage was deduced. The indicator of permeability reduction rate of long core was introduced and used to evaluate the impact of the deposition of each short core on the permeability. Through analysis and comparison, deposition and blockage occurred in the front and middle of the long core, and the maximum permeability reduction rate reached about 0.04%. The results showed that although near-miscible displacement could improve the oil recovery, there was still the possibility of potential blockage which should be carefully considered in the design of the gas injection scheme. [ABSTRACT FROM AUTHOR]

We use numerical simulations of circumplanetary disks to determine the boundary between disks that are radially truncated by the tidal potential and those where gas escapes the Hill sphere. We consider a model problem, in which a coplanar circumplanetary disk is resupplied with gas at an injection radius smaller than the Hill radius. We evolve the disk using the Phantom smoothed particle hydrodynamics code until a steady state is reached. We find that the most significant dependence of the truncation boundary is on the disk aspect ratio H / R. Circumplanetary disks are efficiently truncated for H / R ≲ 0.2. For H / R ≃ 0.3, up to about half of the injected mass, depending on the injection radius, flows outward through the decretion disk and escapes. As expected from analytic arguments, the conditions (H / R and Shakura–Sunyaev α) required for tidal truncation are independent of planet mass. A simulation with larger α = 0.1 shows stronger outflow than one with α = 0.01, but the dependence on transport efficiency is less important than variations of H / R. Our results suggest two distinct classes of circumplanetary disks: tidally truncated thin disks with dust-poor outer regions, and thicker actively decreting disks with enhanced dust-to-gas ratios. Applying our results to the PDS 70 c system, we predict a largely truncated circumplanetary disk, but it is possible that enough mass escapes to support an outward flow of dust that could explain the observed disk size. [ABSTRACT FROM AUTHOR]

Airlift reactors (ALRs) are widely used in the chemical, petrochemical biological industry. A fundamental understanding of the flow field in these airlift reactors are necessary for efficient design and scaling up. In this work, the behavior of the flow field is investigated using the Euler–Eulerian approach. The liquid phase is modeled as continuous and the gas phase is dispersed in the form of bubbles. Three dimensional (3 D) transient computational fluid dynamics (CFD) simulations are performed to characterize flow behavior in ALR. The spatio-temporal variations in the flow field are quantified and an optimum liquid level in the ALR is determined. Various gas source locations are chosen and their effects on bubble plume motion are analyzed to find an optimum gas injection point that supports plume oscillation. Further, CFD simulations are performed to identify the prevailing flow regime in ALR for various gas source locations, and it is compared with experimental observations. The homogeneous and heterogeneous flow regimes are observed at lower and higher flow rates, respectively. The bubble size distribution is predicted using population balance equations through bubble coalescence and breakage models with interphase force formulations. This is computed through the discrete method of moments. The bubble size distribution is found to be narrow at lower gas flow rates and wider at higher gas flow rates. These predictions provide a unified description to characterize flow regimes in ALR. [ABSTRACT FROM AUTHOR]

For fault-controlled fractured-vuggy reservoirs, the development characteristics of bottom water flooding and water and gas injection flooding under multi-well conditions must be clarified due to the structural complexity. To address this issue, we designed and manufactured fault-controlled physical experimental models based on the geological model of Tarim Oilfield and conducted flooding experiments. The results demonstrate significant variations in bottom water flooding characteristics due to differences in flow capacity within fractures, cavity area in caves, and filled area in caves under different filling modes. Different bottom water rates exhibit varying abilities to overcome gravity and breakthrough capillary resistance, significantly impacting the bottom water flooding characteristics. During the bottom water flooding period, the positioning of production wells primarily affects the macroscopic sweep range, while the filling modes significantly influence the distribution of remaining oil within individual caves. Throughout the three periods of multi-well water and gas injection, the early water injection stage mainly focuses on mobilizing "insufficiently controlled remaining oil" and some "attic remaining oil," and the middle gas injection stage primarily targets the attic remaining oil. Finally, the late water injection stage aims to lift the oil–gas–water interface and improve oil displacement efficiency. Furthermore, different water and gas flooding directions affect displacement resistance in each channel and the longitudinal sweep range. This paper identifies the direction for the life cycle production of fault-controlled fractured-vuggy reservoirs and presents a mechanistic explanation. [ABSTRACT FROM AUTHOR]

The problem of optimizing water and gas injection to displace heavier oil components used in fuel production is solved. Several initial oil compositions in the reservoir and various mixtures of injected substances are considered. Numerical optimization is automated in such a way that for a fixed amount of injected pore volumes, the composition of the injected mixture is automatically changed and the most favorable composition is selected, which increases the oil-recovery factor. It is shown that for various initial oil compositions, the displacement efficiency, depending on the amount of injected pore volumes of more valuable components, qualitatively coincides. In this regard, optimization of the injection of a mixture consisting of four components is studied for one of the initial compositions. The processes occurring during injection of the optimal composition are calculated on a finer grid. [ABSTRACT FROM AUTHOR]

The formation of the plasma current spike at the end of the thermal quench (TQ) phase is studied systematically, which is found to strongly correlate with the onset of the 1/1 kink-tearing reconnection only in the simulation results presented here. The magnetohydrodynamic activity on the q = 1 surface plays a critical role in the spike formation and the disruption process. In particular, when the safety factor in the magnetic axis q0 exceeds 1, the plasma major disruption transits into successive minor disruptions, and the start of the TQ phase is delayed. [ABSTRACT FROM AUTHOR]

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Intensifying hydrogen use in the blast furnace is a key technology for significant coke and CO2 emissions reductions. The most straightforward approach is the implementation of high hydrogenous gas injection rates in the BF tuyeres. Yet this solution has not been widely implemented due to a lack of understanding of the impact on the furnace's internal state. In this paper, a newly developed BF mathematical model is presented and validated on operation data. The model is next applied to investigate the effect of hydrogenous gas injection on the overall performance and internal state of the furnace. The current state of an industrial BF is used as a starting point, increasing the injection of coke oven gas, natural gas or pure H2 to the maximum where the limits for a safe and stable process are still obeyed. All three gases were found capable of significantly decreasing the coke rate, but only coke oven gas and pure H2 allowed for a significant reduction of the CO2 emissions. It was found that the indirect reduction of H2 is intensified by hydrogen enrichment partially at the expense of indirect reduction by CO. Furthermore, the water gas shift reaction is intensified at increased hydrogenous gas injection, affecting the CO and H2 utilization of the top gas. The study gives an insight into the feasibility of BF processes with high hydrogenous gases injection into the tuyeres and the resulting coke savings. [ABSTRACT FROM AUTHOR]

A fully transient 3D CFD model of an industrial argon bottom-stirred ladle with two eccentric porous plugs was developed. The computational domain included molten steel, slag, air and refractory phases. The slag-air interface was set as a free surface to ensure that the influence of the flow and the heat dissipation at the slag free surface on the temperature of the molten steel can be considered simultaneously. As a result, the model reasonably predicted the velocity and temperature distribution of molten steel, heat losses from the top slag layer and the temperature distribution in the refractory walls due to bottom gas injection. Previous numerical models on heat transfer in ladles have either neglected bottom gas injection, assumed a constant heat flux through the top slag layer or assumed a flat surface. The current mathematical model overcomes the previous limitations, it is capable to predict fluid flow and temperature distribution under transient conditions comparing a flat and a free surface. It is shown that the assumption of a flat surface leads to errors in the numerical predictions, it also predicts heat losses by the top slag surface and the refractory walls. [ABSTRACT FROM AUTHOR]