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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 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]

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]

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]

For the high temperature (130 °C), high pressure (30 MPa), and high salinity (2.5 × 105 mg/L) of formation water conditions in the target block of the Tarim Basin Oilfield in northwest China, dodecyl hydroxy sulfobetaine surfactant was evaluated for its foaming performance, thermal stability, adsorption performance. The evaluation results showed that the surfactant exhibited good foaming ability and thermal stability than the general carboxy betaine under the above harsh conditions. The static adsorption of the surfactant on the surface of quartz sand particles was less than 1 mg/g with a concentration of less than 0.4%, which met the requirement for foaming agent adsorption. Moreover, the results of core displacement experiments indicated that, when simultaneously injecting 0.4% foaming agent and gas at a volume ratio of 3:7 into the cores of 38 mD, 161.4 mD, and 478.7 mD, foam with low mobility of less than 2 mD/cP could be generated; in the 57.3 mD Berea core, the resistance factor of foam generated by 8 cycles of injecting gas-liquid alternately with gas-liquid volume ratio ranging from 0.2:0.1 to 0.4:0.1 was nearly 20, and the residual resistance factor was greater than 5 after 5 PV of continuous gas injection. The results of the study can guide the selection of foaming agents for gas mobility control in high-temperature and high-salinity sandstone reservoirs. [ABSTRACT FROM AUTHOR]

Behaviors of runaway electrons have been investigated by injection of argon impurity gas during the low-density hydrogen discharges in the STOR-M tokamak. Argon gas is puffed using a fast electromagnetic gas puffing valve with various amounts of gas puffed at different injection times. It has been found that puffing of an appropriate amount of gas can suppress the already generated runaway electrons evidenced by the intensity reduction of the hard X-ray (HXR) radiation caused by the impact of runaway electrons on the STOR-M chamber wall. On the other hand, excessive argon gas puffing causes earlier termination of the discharge. [ABSTRACT FROM AUTHOR]

This paper employs computational fluid dynamics (CFD) simulations with an eddy dissipation concept model (EDC) and a skeletal reaction mechanism (SK17) to analyze the impact of hydrogen addition on the premixed combustion mode of producer gas (PG) fuel in a cyclonic flow combustion chamber. The results, validated against measured wall temperature data, demonstrate a minor discrepancy between simulation and experiment. The studied result showed that injection of hydrogen into PG fuel combustion elevates the temperature of the combustion process, which can be indicated by the average temperature across the combustion chamber, outlet temperature of exhaust gas, and reactive radical species. However, increasing H2 injection over 20% results in strongly increasing CO formations. Compared to a fixed thermal input case, hydrogen injection with a variable input power resulted in a higher combustion temperature and increased emissions of both CO and NO. The maximum CO emission reached approximately 1246 ppm, while NO peaked at around 75 ppm, both observed at a 30% hydrogen injection rate. The key finding of this study revealed that direct injection of hydrogen to the combustion under the condition of a given equivalence ratio is unfavorable due to insufficient oxygen for the reaction, leading to an increase in CO emissions. The optimal condition would be a hydrogen injection below 20%, which produces low CO and NO emissions. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Water control is an effective method to enhance the oil recovery in the high water-cut reservoir. It is proved that the water production can be reduced by the entrapped gas in the oil field. But the mechanism is not well studied. In this paper, the mechanism of enhanced oil recovery by entrapped gas is studied by experiments and numerical simulation. Based on the core flooding tests and simulation study, the increments of oil recovery caused by entrapped gas are 8% and 2%, respectively. After the gas is entrapped in the core sample, the water relative permeability is decreased by 10.5% and the oil relative permeability is only decreased by 3.5%, which proved that the entrapped gas has a dramatic effect on blocking water phase. The more gas is entrapped, the more oil is produced. Different methods to achieve entrapped gas are also discussed, simultaneous water, and gas injection is a preferred entrapped gas formation method than gas injection method and water alternating gas injection method. Under the immiscible condition, the entrapped methane has a better performance on enhancing oil recovery than the entrapped nitrogen. [ABSTRACT FROM AUTHOR]

In order to determine the MMP using the slim test, the use of an appropriate criterion is inevitable. But there is no standard method or criterion for interpreting the data in this experiment to determine the MMP. However, various criteria such as linear intersection (LI), oil recovery factor (ORF), and break-over pressure (BOP) are currently used to ascertain MMP. However, these criteria are not perfect and need to be improved. In this paper, a slim test is first performed for a live-oil and methane. Then, the mentioned criteria have been modified. Modified ORF and BOP criteria are named MORF and MBOP, respectively. All the results from the various criteria are compared, and an interval for the MMP is determined. Finally, for the performed slim tube test, a pressure range of 6061.71-6258.94 psi has been determined. The novelty of this study is to provide more methods to determine the MMP interval, as well as criteria that can be used for a wider range of laboratory data. The application of the results of this study will be to determine a range for MMP, so that if the gas injection pressure is in this range, the injection conditions will be miscible. [ABSTRACT FROM AUTHOR]

The injected fluid can chemically react with reservoir rocks and fluids, which changes the properties of petroleum and rocks. Consequently, oil recovery rates are subject to change during the EOR process. Therefore, the study of chemical reactions during EOR process is important. During the CO2 injection, the deposition of asphaltene, and the change of minerals, dissolution and deposition can occur at the same time. Dissolution of rock minerals can increase permeability and effective porosity, but precipitation of asphalt and deposition of these minerals can have the opposite effect. This study investigates the CO2 flooding process in heavy oil reservoirs containing highly permeable sandstone and assesses the effect of orientation on oil recovery and rock-fluid interactions. The results show that due to the gravitational stability in the vertical configuration, there is more oil recovery, mineral solution, and asphaltene sedimentation in the vertical configuration compared to the horizontal configuration. The percentage of asphaltene in the sandpacket model was 1.92 weight percent vertically and 1.18 weight percent horizontally. The increase in porosity for vertical was 2.6% and 1.1% for horizontal infusion. From this it can be concluded that the dissolution of minerals is higher with vertical injection than with horizontal injection. [ABSTRACT FROM AUTHOR]

Coal bed methane (CBM) is a gas resource associated with and symbiotic with coal, which refers to the hydrocarbon gas stored in the coal seam, with methane as the main component, which belongs to unconventional natural gas. The development and utilization of CBM has the effect of achieving multiple things in one fell swoop: clean energy, commercialization can produce huge economic benefits. At present, rod pump, screw pump and other lifting technologies commonly used in CBM drainage and production have poor adaptability, short pump inspection period, and it is difficult to enter horizontal section in horizontal well. Aiming at this problem, a new method of efficient CBM lifting is proposed by adopting dual-pipe gas lift technology. In this paper, the basic principle of double tube gas lift is analyzed, the optimization design of gas injection volume, coiled tubing size and coiled tubing running depth is carried out, and the field technology application of vertical and horizontal Wells is carried out. The results show that the dual tube gas lift technology has good adaptability in the deliquification of CBM, and the field application has achieved good production results. After the process modification, gas production of CBM Wells increases continuously, while water production decreases gradually, with the maximum gas rate exceeding 2400 m3/d. According to the latest production data, well L31 has been in steady production for more than 9 months, with an average gas rate of 1294.56 m3/d, which greatly exceeds the capacity before the transformation. Because there are no moving parts in the wellbore, the pump inspection period is greatly improved, and it has the potential to be widely applied in CBM. [ABSTRACT FROM AUTHOR]

Tight glutenite reservoir in Mahu area are usually put into production by volume fracturing of horizontal wells. In the process of production, there are some problems such as rapid production decline, low recovery factor, and so on. Therefore, experimental study of natural gas flooding to improve the recovery of tight glutenite reservoir was carried out. Using cores of different diameter sizes from the target interval of the target area, the whole development process of different gas injection speeds and different development methods is simulated by the core displacement devices with high temperature and high pressure resistance. The characteristics of exhaustion, displacement, development effect, and action mechanism were evaluated and analyzed systematically. The study shows that the better the physical properties of the tight glutenite, the higher the recovery degree of the exhaustion development. As the pressure is reduced from 55MPa to 10MPa, the recovery degree can reach about 6%. Natural gas flooding after exhaustion can greatly improve oil recovery. The results of laboratory experiments show that the recovery efficiency of natural gas flooding after depletion can be improved by 38%–62%. The higher the gas injection rate is, the lower the final recovery rate is. With the displacement velocity increasing from 0.02 ml/min to 0.1 ml/min in laboratory experiments, the corresponding ultimate recovery rate decreased from 67.03% to 44.67%. Therefore, field operations need to control the gas injection rate to ensure higher gas flooding recovery. According to the experimental results of natural gas flood-soaking-natural gas flooding, the final recovery is 38.54% under miscible condition. The recovery of gas flooding stage before soaking is 27.97%. Compared with natural gas flooding, the oil displacement efficiency can be improved by nearly 10% in the development mode of natural gas flooding-soaking-natural gas flooding, which is due to its mechanism including the following three stages. First is near-miscible flooding which plays a role in intergranular pores, micro-fractures, and pressure fractures in the gas flooding stage before soaking. Second is miscible dissolution replacement which plays a role in intergranular dissolved pores in the soaking stage. Third is gas carrying oil recovery which plays a role in pressure fractures in the gas flooding stage after soaking. Finally, the development mode of natural gas flooding-soaking-natural gas flooding can achieve enhanced tight glutenite recovery. [ABSTRACT FROM AUTHOR]

The coal body's gas environment transforms during the CO2 fire prevention procedure from an oxygenated ambience to a CO2 gas ambience, which in turn prevents the coal body from continuously oxidizing. To investigate the effect of sudden changes in the gas environment to which the coal body is exposed on the microscopic group reactions, the free radical parameters such as ESR in situ spectra, line widths, g-factors, and free radical concentrations of the coal bodies during the gas atmosphere transition at different temperature moments were measured. The findings are as follows: as the injection temperature point for CO2 rises, the spectral peak height increases, and the paramagnetic center of coal shifts at lower temperature in CO2 atmosphere than in dry air atmosphere. After the abrupt change of gas environment, free radical levels first decrease and subsequently rise. Furthermore, the general development rate of free radicals can be slowed down by injecting CO2 at lower temperatures. Meanwhile, at lower temperatures, the higher the temperature point of the minimum g value is, the smaller the maximum g value is. Changes in a gas atmosphere, sudden decrease in line width of ESR spectra of coal bodies, and the line width finally stabilizes around 0.45. CO2 injection at 70°C has the best inhibitory effect on free radicals. [ABSTRACT FROM AUTHOR]

During lean gas reinjection after depletion in high-pressure and low-permeability reservoirs, the fluid composition in the formation changes greatly, the microscopic interaction process among fluids is complex, and the microscopic mechanism of lean gas flooding is not clear to us. In this article, the microscopic experiments were carried out in high-temperature and high-pressure micro-visualization experiment apparatus of independent research and development. The microscopic interaction process between lean gas and formation fluid before and after depletion was studied on the porous models made of glass by etching. The flow law of lean gas after depletion and the mechanism of microscopic oil displacement were discussed. The results from experiments conclude that lean gas flooding should alleviate the Jamin effect caused by gas separated from oil during depleted production. Under the reservoir conditions, the oil is produced by lean gas displacement force primarily, by lean gas extraction for auxiliary. The water barrier prevents the contact between lean gas and residual oil. In unswept areas of lean gas, the residual oil is difficult to be produced as the poor diffusion of lean gas through water barrier into residual oil. While in swept area, lean gas can peel off water film gradually, then contact with residual oil directly, and then drive out oil by dissolving and extracting. Lean gas flooding in high-pressure and low-permeability reservoirs can enhance oil recovery further after depleted production. [ABSTRACT FROM AUTHOR]

This study aimed to address the challenges and strategies to determine the critical rate of CO2 injection into a carbonate depleted gas field. In this research, the critical rate is the maximum allowable injection rate before formation damage initiation. The cause of formation damage could be due to in-situ mobilization or trapping of migratory fines resulting in plugging the flow path. This study performed a thorough investigation of a different rock-fluid system to evaluate the safe injection limit, as the critical rate is different for each rock-fluid system. The geochemical effect of CO2 injection toward carbonate formation was also investigated in this research. Other than that, the porosity and permeability changes due to CO2-brine-rock multiphase flow characteristics were considered to understand the feasibility of CO2 sequestration into carbonate formation. This research discussed experimental design to mimic the CO2 injection scenario of CO2 into carbonate depleted gas field. Therefore, several core flooding experiments were conducted under reservoir conditions using representative native cores, CO2, and synthetic formation brine. Abrupt changes in differential pressure (ΔP), analysis of effluent collected after CO2 multi-rate flow, and pH reading are the key indicators to consider that the condition has reached a critical rate. The experimental result demonstrated the existence of fines migration, scale formation, and salt precipitation after the core was subjected to supercritical CO2 multi-rate flow. Considering these issues and challenges associated with injectivity, this study recommended a maximum injection rate prior to field scale injection. [ABSTRACT FROM AUTHOR]

Renewable sources of energy help mitigate the environmental concerns associated with fossil fuel combustion and in meeting the ever-increasing energy demand. The use of HHO gas in I.C. Engines becomes promising in this context. HHO gas is a mixture of hydrogen and oxygen in the ratio 2:1, produced by the electrolysis of water. In this research, alkaline electrolysis was used for producing HHO gas using KOH as an electrolyte. This HHO gas was introduced in the intake manifold of the C.I. engine, making it operate in dual-fuel mode. The effects of HHO gas addition on engine performance and emissions were investigated. The variation of diesel injector protrusion (DIP) by +/− 1 mm from its normal position was also studied. This was achieved using washers of varying thicknesses. Three different HHO gas injection locations, namely port, manifold, and upstream, were compared to determine the most suitable position. The simultaneous evaluation of the effects of DIP and HHO injection location makes this study unique. BSFC, peak pressure, HC, CO, CO2 and smoke emissions were observed to be lower, while BTE, NOx and O2 emissions were enhanced for the optimum condition of + 1 mm DIP, PI with 1.63 LPM of HHO gas. [ABSTRACT FROM AUTHOR]

Gas injection is one of the most widely used enhanced oil recovery methods in hydrocarbon reservoirs that has been attracting considerable interest of the oil and gas industry over the years. With the rapid development of research areas involved in gas injection, understanding the evolutionary pattern and significant milestones of collective knowledge development has a newfound urgency. This study used a bibliometric approach to identify knowledge domains, intellectual milestones in the development of important research areas, evolutionary stages, the technical state of the art and emerging trends concerning gas injection. The document co-citation network offers an intuitive overview of the intellectual structure and the state of the art of this specialty. The bibliometric indicators provide quantitative analysis for identifying particularly impactful contributions within a specific field of research, such as the landmark works with the most citation counts, the structurally significant articles with the highest betweenness centrality, and the most active areas detected by the strongest citation bursts. The timeline visualization draws on Shneider's scientific evolution model to track the evolutionary stages of gas injection consisting of knowledge conceptualization, research instruments accumulation, and technology integration and application along historical and philosophical lines. Through structural variation analysis, we explored potentially transformative contributions and emerging trends which may boost the development and application within and among relevant fields. The methodological approach taken in this study provides a generic method for conducting a systematic review of a scientific discipline. [ABSTRACT FROM AUTHOR]

The gas in soft cohesive sediments tends to transport through fractures or cracks, and the study on fracture toughness of soft soil is an important component of the research on gas migration. A method for measuring fracture toughness of soft sediments is proposed in this paper. The gas injection tests on soft soil at constant flow rate were conducted, and the fracture toughness of soft soil could be calculated combined with the theory of linear elastic fracture mechanics based on the gas pressure and the orifice diameter. Through direct observation of the bubble growth in Laponite RD transparent soil, the law of gas pressure variation and the mechanism of bubble fracture growth in soft soil were further verified. The methods and instruments proposed in this paper are convenient and easy for operating, which are suitable for measuring fracture toughness of soft soil in laboratory. The fracture toughness of soft soil obtained by the method presented in this paper is consistent with the measurements of the in-situ soft clay proposed in the literature, which suggests that the fracture toughness measurement method of soft soil proposed in this paper is reasonable. [ABSTRACT FROM AUTHOR]

The objectives of this article it to present a water alternating gas (WAG) process evaluation methodology for a giant middle eastern carbonate reservoir. The methodology involves enhanced oil recovery through an immiscible hydrocarbon water alternating gas (WAG) injection method. Although water alternating gas injection is a proven enhance oil recovery technique and has been around for some time now, only a limited published literature is available on complete evaluation of immiscible WAG process in field application. This article aims to bridge the gap by presenting a detailed study of immiscible water alternating gas evaluation process. In this article a complete methodology for evaluating a water alternating gas injection recovery technique is presented. It includes optimization of WAG cycle length, WAG ratio, production constraints, injected gas compositions, WAG duration, and WAG slug size. The work presented in this article could aid oil field operators to understand the impact of different parameters on immiscible WAG injection process and potentially help them to optimize production from their fields. [ABSTRACT FROM AUTHOR]

Visualization experiments and numerical simulations of two-phase flow are conducted to study the pressure fluctuation characteristics of oil-gas flow in horizontal pipes. The two-fluid model based on the Eulerian–Eulerian method is adopted, and the bubble number density equation (BNDE) is introduced to the simulation to predict the bubble size and distribution within the pipe. The bubble size and pressure variations in the pipe obtained from the simulations agree well with the recorded values from the experiments. The fast Fourier transform (FFT) algorithm is used to analyze the characteristics of pressure fluctuations, and the results show that the sudden pressure increase in the pipe sections is related to gas injection. The bubble number density increases with liquid flow rate (Ql), which causes the oil-gas flow to be more turbulent while increasing the amplitude of high-frequency fluctuations. The maximum amplitude for the dominant frequency is observed near the pump inlet for low liquid flow rates. At high liquid flow rates, more liquid vortices are found near the gas orifice, and there is a maximum amplitude for the dominant frequency in this section. Due to the high swirling strength at larger inlet gas volume fraction (IGVF), there is an obvious increase in the amplitude of low-frequency fluctuations, while the amplitude of high-frequency fluctuations is nearly the same under all IGVF. [ABSTRACT FROM AUTHOR]

Investigation of gas migration in saturated soil is of great theoretical and practical significance in marine science and engineering. The transport of gas bubbles in soil and its effects on soil physical and mechanical properties can be further studied. Gas injection and permeability tests were conducted using a self-developed oedometer with gas injection and water infiltration. Before the gas injection test, the remolded saturated soil was consolidated in an oedometer device to an effective vertical stress of 100 kPa. Gas injection tests were then performed to investigate the transport mechanism of bubbles in saturated soil and the changes in water permeability after gas injection. The results show that it is difficult for gas to migrate through capillary invasion and fracturing from the pore scale owing to the high gas entry pressure in fine-grained sediments. Hence, initial gas migration mechanism in pore scale is elastic-plastic expansion. The scale of cavities expands from micron to millimeter during gas injection, and gas pressure for fracturing reduces with the expansion of cavities. The fracturing initiated in millimeter scale and gas invades further into the soil. Interconnections of cavities and cracks resulting in an increasing of drainage rate and coefficient of permeability. [ABSTRACT FROM AUTHOR]

An unmanned airship was used to overcome the limitations of conventional aeromagnetic exploration systems. The airship was fabricated from non-magnetic fibre-reinforced plastic and urethane cloth, and filled with helium. The maximum payload is 10 kg and the flight time (with all equipment installed) is approximately 1 h. The airship is simple to move and store prior to gas injection, and easy to handle in the field because of its small size. An automatic flight algorithm enables stable and efficient exploration. A radiofrequency modem and long-term evolution router connect the airship to ground control even when it is not in the line of sight. Magnetic data and airship location are monitored in real time and verified using a helicopter. The airship showed high efficiency. [ABSTRACT FROM AUTHOR]

CO2 injection and water-alternating-gas injection are EOR methods for improving oil recovery. This paper shows Water alternating gas (WAG) and continuous gas injection experiments with CO2 in secondary recovery. Experiments were performed in sand-packed-model. The continuous gas injection experiments were conducted at 3800, 4200, 4600 and 5000 psi, then two WAG experiments was completed at 3800 psi. Also temperature was 190 °F (the reservoir temperature) in all experiments. Six tests were conducted to investigate continuous CO2 and WAG injection under the reservoir condition. In the first test, 1.2 PV (pore volume) of CO2 was injected into sand-packed-model at pressure of 3800 psi and temperature of 190 °F. Amount 1.2 PV of CO2 was injected into sand-packed-model at 4200 psi in the test 2. In third one, 1.2 PV of CO2 was injected at 4600 psi and 1.2 of PV CO2 was injected at 5000 psi in forth one. Water alternating gas injection experiments with CO2 were including two tests. In the first one, 0.3 PV of CO2 and 0.9 PV of brine were injected consecutively into model. In the second one, 0.3 PV of CO2 and 0.3 PV of brine were injected respectively into model and this test was completed in two cycles. The results indicate that increase of injection pressure enhances oil recovery in continuous CO2 injection and increase of injected CO2 increases oil recovery in WAG process. Also WAG injection increases oil recovery more than CO2 continuous injection. [ABSTRACT FROM AUTHOR]

Nitrogen (N2) and carbon dioxide (CO2) gases injection yield substantially various recovery ways. Here, a one-dimensional mathematical model is applied comprising of mass balances for explaining gas sorption and flow, and a geomechanical relationship to describe the permeability changes during gas injection. That's why numerical simulations for investigating the performance of injecting flue gas mixture in enhanced coal bed methane (ECBM) recovery are represented. Significant intuitive features are found regarding the gas flow dynamics at the time of displacement and influences of sorption on ECBM operation. The study revealed that the injection of pure CO2 causes much reduction in cleat permeability, but pure N2 is injected to increase the permeability without any loss of injectivity. Therefore, pure CO2 causes more efficient displacement in terms of total CH4 recovery, while the addition of N2 to the mixture assists to make quicker the initial methane recovery. [ABSTRACT FROM AUTHOR]

Because gas injection into geological formations is a common technology deployed for enhanced oil recovery (EOR), it is important to understand at the molecular level the relations between competitive adsorption and fluid mobility at the single-pore level. To achieve such an understanding, we report here molecular dynamics simulation results to document structural and dynamical properties of n-octane confined in slit-shaped alumina and graphite pores in the presence of CO2 or H2S. The substrates are chosen as proxy models for natural hydrophilic and hydrophobic substrates, respectively. It was found that CO2 and H2S could displace n-octane from alumina but not from graphite surfaces. Analysis of the results demonstrates that more attractive n-octane – surface and weaker CO2/H2S – surface interactions in graphite compared to alumina are responsible for this observation. Regardless of pore type, the results suggest that adding CO2 or H2S suppresses the diffusion of n-octane due to pore crowding. However, the mechanisms responsible for this observation are different, wherein preferential adsorption sites are available on the alumina surface for both CO2 and H2S, but not on graphite. To contribute to designing advanced EOR technologies, possible molecular mechanisms are proposed to interpret the results. [ABSTRACT FROM AUTHOR]

A concurrent computational and experimental study of self-excited combustion dynamics in a model configuration of a lean direct injection (LDI) gas turbine combustor is described. Both acoustically open and closed configurations are considered in the computations and analyzed using dynamic mode decomposition (DMD) to identify the frequency couplings. In the acoustically open case, simulations are carried out with unperturbed and perturbed inlet mass flow rates at the dominant frequencies observed in the acoustically closed geometry. In the unperturbed case, a vortex breakdown bubble (VBB) is shown to be the dominant flow structure, while the perturbed simulations indicate the presence of swirling hydrodynamic modes and the possibility of coupling between hydrodynamics and acoustics as a mechanism for sustaining thermo-acoustic instabilities. Detailed analysis of the acoustically closed combustor simulation reveals the presence of another important hydrodynamic mode, the precessing vortex core (PVC). The possibility of nonlinear coupling between the acoustics and PVC modes is also revealed. The thermo-acoustic coupling is further analyzed by the Rayleigh index frequency spectrum. [ABSTRACT FROM AUTHOR]

During the cyclic gas injection of gas condensate reservoir with bottom or edge water, complicate phase changes and energy conversion take place. A new calculation model for condensate oil saturation is established based on the principle of volume conservation. Moreover, the calculation model considers the influencing factors such as retrograde condensation, connate water evaporation, elastic expansion of reservoir rocks, and external dynamic water invasion. Combining the reservoir fluid property and dynamic production data, this model can calculate the condensate oil saturation under different reservoir pressures quickly. The Case study shows that the condensate oil saturation obtained by this model coincides with the indoor depletion experiment and reservoir numerical simulation. Meanwhile, the sensitivity evaluation of the above influencing factors is carried out. Furthermore, the factors impacting the calculated results from high to low are external dynamic water invasion, elastic expansion of reservoir rocks and connate water evaporation. [ABSTRACT FROM AUTHOR]

The study aims to predict the physical properties of Iran crude oils using modified pressure-volume-temperature (PVT) equation of state. The modification was theoretically developed and then performed by using data of 30 black oil samples representing all active oil producing areas of Iran. The equation enables to predict the bubble-point pressure, oil formation volume factor, gas–oil ratio, oil density, crude oil gravity, gas gravity, and gas formation volume factor of black oils with average relative errors ranging from 0.01% to 10.713%. Calculation sensitivity of the proposed Peng-Robinson is determined by testing four oil samples collected from different locations in Iran and comparing the measured PVT properties with those calculated from Peng-Robinson. These evaluations show an excellent agreement between the measured properties and calculated ones. The estimation of reservoir liquid and gas properties from Peng-Robinson is often needed when detailed laboratory PVT data are not available. [ABSTRACT FROM AUTHOR]

It has been well known that, in GMA welding, various welding phenomena are largely affected by the type of shielding gas used. However, up to the present time, almost no attempt has been made to utilize 'gas composition' for controlling welding phenomena. This study focused on this point and, thus, an investigation was made to understand how dynamic gas compositional modification affected various welding phenomena. In this study, pulsed Ar gas was injected periodically into CO2 shielding gas so that the gas composition of arc atmosphere largely modified in a very short period of time. It was found that this quick gas compositional change from CO2 to Ar led to a large decrease in arc voltage and an arc shape change from a constricted shape to a flare shape and that a molten droplet formed at the electrode tip during the CO2 period was released due to a sudden change in force balance between the molten droplet and the arc. The increase in current stimulated by the voltage drop may have assisted the metal drop detachment due to an increase in electromagnetic pinch force. If the cycle of this periodical Ar gas injection was selected to be shorter than that of repelled metal transfer in CO2 atmosphere, the repelled transfer was avoided and stable drop transfer occurred instead with far less spatter. Appropriate selections of the duration time of pulsed Ar gas injections avoided spray transfer which might cause undesirable finger-like penetration profiles. This new conceptual welding method, namely 'Pulsed Gas MAG Welding', required only a small amount of Ar gas to obtain the effects mentioned above. [ABSTRACT FROM AUTHOR]

In this work, the efficiency of CO2-foam injection for enhanced oil recovery (EOR) is investigated. Six floods were performed on sand pack columns. Pure water injection, WAG injection and simultaneous injection of CO2 and surfactant solution with various concentrations were conducted. Notable difference was observed between oil production in secondary surfactant assisted WAG and other injection scenarios. The experimental work in this research shows that increase in concentration of surfactant in the injection process results in mobilization of more oil that may not have been achievable by using water flooding and WAG flooding methods individually. [ABSTRACT FROM AUTHOR]

Time lapse seismic is a vital component of the monitoring and verification of virtually any geosequestration project. Stage 2C of the CO2CRC Otway project is designed to test the limits of land 3D time-lapse (4D) seismic in the monitoring of small-scale CO2 injection. The 4D seismic monitoring program of Stage 2C of the Otway Project includes a baseline survey (BL); three monitor surveys (M1–M3) obtained during the injection of CO2-rich gas into the saline aquifer at a depth of 1.5 km at the injection intervals of 5, 10, and 15 kt; and two post-injection surveys (M4 and M5), acquired one and two years after the end of injection. Reliable time-lapse changes among the 4D surveys were obtained using a buried receiver array. Analysis of the seismic cubes and attributes demonstrates that during and after injection the plume spreads laterally only in southeastern direction. The results demonstrate strong time-lapse signal corresponding to the injection level and the absence of any observed leakage into the overburden. The plume evolution is reliably observed and traced from M1 to M5 surveys with most of the changes occurring between the BL and M4 surveys. [ABSTRACT FROM AUTHOR]

The methane from two coal seams are usually produced in the same production well, and the commingled production process is of low efficiency. In order to enhance the methane recovery from the two coalbeds, a 'multi-branch U-shaped' well is introduced to double-coal seams. This well structure can perform a single layer or commingled production. There are at least 10 production methods for the new well: (1) Drainage gas recovery of upper coal seam, (2) gas injection huff and puff of upper coal seam, (3) gas injection displacement of upper coal seam (including continuous gas injection or intermittent gas injection), (4) drainage gas recovery of lower coal seam,(5) gas injection huff and puff of lower coal seam, (6) gas injection displacement of lower coal seam (including continuous gas injection or intermittent gas injection), (7) drainage gas recovery of both coal seams, (8) gas injection huff and puff of upper coal seam and drainage gas recovery of lower coal seam, (9) gas injection huff and puff of lower coal seam and drainage gas recovery of upper coal seam, and (10) gas injection displacement of both coal seams. Meanwhile, five production strategies are investigated by simulations with reference to the special well structure. Combined with the coalbed methane field operation, the well is conducive to carbon dioxide huff and puff, the optimized production strategy is: water drainage in the early period, and carbon dioxide huff and puff at middle-late stages of development. The new well structure can greatly improve CBM recovery. [ABSTRACT FROM AUTHOR]

Due to the significant impacts of CO2-oil miscibility, reservoir heterogeneity, and injection pattern on oil production, a fascinating experimental investigation is provided. The outcomes express that CO2 consumption in homogeneous cores are lower than heterogeneous cores. A small amount of permeability heterogeneity as one of the indications of heterogeneity, can highly effect on the performance of miscible and immiscible injections. On the miscibility viewpoint, multi-contact miscible injections have better performance than immiscible injections in range of 7.2% − 16.4%. Also, the injection patterns comparisons express that best choice for pattern injection is water alternating gas injection. [ABSTRACT FROM AUTHOR]

In the soft coal seam with ultra-low permeability, the effect of permeability enhancement by hydraulic fracturing or stress relief methods is not ideal due to the closure of fractures. Injecting foreign gas into the coal seam can replace part of the gas adsorbed in the coal matrix and drive the coal seam gas to the drainage borehole, so as to achieve the purpose of promoting gas drainage. In this paper, we established a fluid-geomechanics coupling model for the high-pressure air injection promoting gas drainage. This mathematical model contains governing equations of ternary gases competitive sorption and transport, and deformation response of coal material, reflecting the interactions among gas mixtures and coal seam. The model is solved by the finite element method to simulate the high-pressure air injection promoting coal seam gas drainage through floor roadway drillings in studied Coal Mine. The gas pressure of CH4, N2 and O2 is comparatively analyzed, and the effective drainage area is obtained. It is confirmed that the air injection can enhance gas drainage by the competitive adsorption and pushing effect. Meanwhile, numerical simulations are carried out to optimize the borehole arrangement. When the operation continues 120 days, the effective areas in studied case are 10.1, 11.23, 11.35, and 6.23 × 103 m3 for borehole spacing of 6 m, 8 m, 10 m and 12 m respectively. The borehole spacing of 10 m is the optimal arrangement in the studied case, owing to its greater effective drainage volume and fewer boreholes. These provide a foundation for guiding the operation of air injection promoting coal seam gas drainage in the field. [ABSTRACT FROM AUTHOR]

CO2 gas-shielded arc welding, which is widely used in the industrial world, has been recognized as an efficient and economical GMA welding process. However, its characteristic repelled transfer produces a large amount of spatter which results in costly cleanup and, thus, practical methods to overcome this weakness have been highly demanded. In the series of this study, 'Pulsed Gas MAG' welding was proposed as a new approach to reducing spatter, in which Ar gas pulses were periodically injected into CO2 shielding gas so that gas composition of arc atmosphere was largely modified in a very short period of time and a metal droplet formed at the electrode tip during CO2 atmosphere was released before repelled transfer had occurred. In this report, the influence of parameters of Ar gas injections, such as frequencies, average gas flow rates and gas injection periods, on the metal transfer was investigated. It was found that synchronous metal transfer stimulated by pulsed Ar gas injections was achieved at any frequencies from 35 to 65 Hz under the conditions of gas injection periods longer than 4 ms and of Ar gas volumes larger than approximately 1mL/pulse. This is because Ar gas injections below these critical levels resulted in lack of time for arc shape changes and metal drop detachment. From these experimental results, a model to explain the metal transfer phenomena was developed. The amount of spatter was reduced to the levels as low as that of the conventional MAG welding with 80 %Ar +20 %CO2 shielding gas mix and penetration profiles were round shape like those obtained in CO2 arc welding. [ABSTRACT FROM AUTHOR]

Gas injection is an effective way to enhance methane drainage in a low permeability coal seam, and the reasonable distance between injection holes and drainage holes depends on effective influence distance of injection gas in a coal seam. For anisotropic permeability of coal seam, the variation of the gas-flow rate from a test hole in the anisotropic coal seam is measured as nitrogen is injected into the injection hole near the test hole. The effective distance regularity is revealed by nitrogen injection in an anisotropic coal seam, and the model of nitrogen injection is established to numerically analyze the aging characteristic of effective influence distance in the anisotropic coal seam. The results show that the permeability in coal seam reduced exponentially with the increase in gas pressure, and it is larger in the direction of parallel to bedding than that in the direction of perpendicular to bedding. The effective distance with nitrogen injection increased exponentially in the direction of parallel/perpendicular to bedding, and the effective distance in the direction of parallel to bedding is bigger than that in the direction of perpendicular to bedding. The optimum distances between injection hole and test hole, with 0.5 MPa of injection gas pressure and 8.36 h of injection gas time, are 2.05 m in parallel to bedding direction, and 1.53 m in perpendicular to bedding direction. This study will have important theoretical and practical significance for a reasonable layout of injection-drainage holes during injecting gas to enhance methane drainage. [ABSTRACT FROM AUTHOR]

Gas injection is one of the most common heavy oil recovery methods. In this study, effect of viscosity reduction of heavy oil on its recovery and production rate during gas injection were investigated. In this regard, governing equations such as continuity and stokes equations were solved using finite element method with assuming specified initial and boundary condition. Numerical results show that production rate for gas injected heavy oil is 50 times higher than that of heavy oil without considering gas injection. Also, simulation results demonstrate the location of high pressure drop zones in porous media. [ABSTRACT FROM AUTHOR]

The aim of the present study is to extract the pore solution from cement pastes and mortars with high W/C ratio by a non-destructive method. The sample is placed in a hydrostatic cell under a confining pressure and an inert gas under high pressure is applied at one end to force a movement of interstitial water. As a result of the non-destructive nature of this method, successive extractions were carried out on cement pastes with W/C ratio equal to 0.7: the first one is directly performed on three initially saturated samples and the second one after drainage and resaturation by two chemically different solutions to observe the exchanges between the saturating solution and cementitious matrix. The chemical analysis results of K+, Na+, SO42−, Mg2+, Ca2+, Li+ and Sr2+ show that the volume of extracted water is representative of concentrations of the various ionic species present in a pore solution of cement pastes. [ABSTRACT FROM AUTHOR]

In this paper, the heat transfer characteristics of a 2D gas–solid spout fluidized bed with a hot gas jet are investigated using computational fluid dynamics-discrete element method. The initial temperature of the background gas and particles in the spouted bed was set to 300 K. The particle temperature distribution after injection of 500 K gas from the bottom, center of the bed, is presented. The simulation results indicate well heat transfer behavior in the bed. Then, statistical analysis is conducted to investigate the influence of inlet gas velocity and particle thermal conductivity on the heat transfer at particle scale in detail. The results indicate that the particle mean temperature and convective heat transfer coefficient (HTC) linearly increase with the increase in inlet gas velocity, while the conductive HTC and the uniformity of particle temperature distribution are dominated by the particle thermal conductivity. The conductive and convective heat transfer play different roles in the spout fluidized bed. These results should be useful for the further research in such flow pattern and the optimization of operating such spouted fluidized beds. [ABSTRACT FROM AUTHOR]

Formation, growth, and detachment of injected air bubble from a submerged needle in stagnant liquid at the different temperature of fluid, investigated numerically. Experiments have been done for validation of numerical simulation results. The injection flow rate of air was varied between 600 and 1200 mL/h in experimental study. Bubble formation, growth, and detachment information were obtained using high speed camera and visual photography technique. Young–Laplace equation that was derived from the force balance on the bubble, was utilized in numerical simulation. A novel method was used for solution of Young–Laplace equation. The bubble diameter, instantaneous contact angle, volume, and other characteristics of bubble were studied at different temperature of operating condition. Also, the enhancement of temperature in Al2O3 nanofluid with 0.01% volume concentration (φ = 0.01%) was compared with deionized water results. The results reveal that by increasing the Al2O3 nanofluid and the deionized water temperature, the diameter, volume, and center of gravity of bubble decrease; however, the instantaneous contact angle increases. Meanwhile, the size of bubble at Al2O3 nanofluid is larger than of that in deionized water at same temperature. Also, the bubble aspect ratio is almost senseless to temperature increment in both deionized water and Al2O3 nanofluid. Eventually, the variation of operating temperature and adding of nanoparticle to the deionized water have significant influence on behavior of growing bubble. [ABSTRACT FROM AUTHOR]

In order to understand the influences of natural draft cooling tower (NDCT) with flue gas injection on pollutant concentrations of the theoretical plume downwash area, an automatic air quality monitoring station was set in the theoretical plume downwash area of NDCT in Qinling power plant to get hourly SO2 and NO2 concentrations over a year. The results show that: 100% 1h average concentrations of SO2 and 99.64% NO2 observations satisfied the requirements of Chinese ambient air quality standard. High pollutant concentrations caused by plume downwash of NDCT with flue gas injection are not observed during the monitoring period, and there are no significant differences (P > 0.05) between pollutant concentrations in the theoretical plume downwash area under the prevailing westerly wind conditions (37.2 ± 24.8 μg/m3) and easterly wind conditions (36.9 ± 22.3 μg/m3), while the concentrations under conditions of west wind speed > 5m/s are significantly lower (P < 0.01) than those under conditions of west wind speed < 1.2m/s. The observations of this study indicate that ground pollutants at high concentration owing to plume downwash would not occur in the theoretical plume downwash area of NDCT with flue gas injection. [ABSTRACT FROM AUTHOR]

Bubble formation in flowing liquid is an important process for wastewater treatment, processing of molten metals, and biological processes. Based on a global balance of force on the bubble, this report describes a new theoretical model for bubble formation during horizontal gas injection into turbulent liquid flow in a vertical tube. This work highlights the importance of choosing the correct drag law in accordance with the bubble size. Five models for drag coefficient are compared, and of these, model III is recommended. Modified detachment criteria are applicable, depending on the liquid velocity. The new analytical model yields good predictions compared with experimental data. Based on the theoretical model, this study investigates the effects of the direction of liquid flow, liquid velocity, gas velocity, and orifice diameter on the bubble formation behavior. [ABSTRACT FROM AUTHOR]

Fibrous filters are commonly used for aerosol purification and sampling. The filtration efficiency has been extensively studied using standard aerosol generators, yet the literature on experimental data and theoretical study concerning the filtration of agglomerates from real engines remains scarce. A filtration efficiency test system was developed to determine the filtration efficiency of two types of filters (uncoated and fluorocarbon coated) loaded by particulate matter (PM) emissions from a gasoline direct injection (GDI) engine. The experimental results showed that the filtration efficiency in terms of PM mass and number increased over time for both types of filters. The fractional efficiency (penetration efficiency) curves for the test fibrous filters rendered a U-shaped curve for particle sizes from 70 to 500 nm, and the most penetrating particulate size (MPPS) decreased over time. A small fraction of accumulation mode particles with the size between 70 nm to 500 nm penetrated the filters while almost all nucleation mode particles with the size below 50 nm were captured by the filters. The filtration efficiency derived from an empirical model based on classical single-fiber theory for laden filters generally agreed with the experimental data for the first 500 s, but suffered a significant deviation by approximately one order of magnitude at 948 s. A better estimate of the filtration efficiency trend with the maximum deviation of about 20% (except for large particles at the high end of the measurement spectra) was obtained by using a revised model which incorporates the effects of the increase in filter solidity, local velocity, dynamic shape factor and effective total length of fibers during the filtration process. © 2017 American Association for Aerosol Research [ABSTRACT FROM PUBLISHER]

Carbon dioxide flooding is a very complicated process, involving phase behavior that could increase oil recovery by means of swelling, evaporating, and lowering oil viscosity. The present investigation reports the results of extensive experimental and theoretical work to determine the viscosity and swelling factor changes of the live oil in the Cheshmeh Khoshk reservoir in southern part of Iran (Ilam District), and also minimum miscible pressure is determined. In this study, we want to study the potential of carbon dioxide injection application in improving oil recovery by simulating a slim-tube experiment. In order to get representative fluid samples of a reservoir, it was necessary that the right operation of mixing the separator oil and gas samples to match the bubble point pressure be carried out. The potential application of the study is that we could have a good estimate of the recovery improvement under carbon dioxide gas injection, which will be the basic input parameter for the economic feasibility study, and also a decision can then be made whether to implement or abandon the prospective project. [ABSTRACT FROM PUBLISHER]

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. Therefore, predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, a new modified cubic-plus-association (CPA) equation of state (EoS) was used to model asphaltene precipitation. This equation is based on a combination of a new physical part and an association term. The new physical part has an evolved cubic equation of state with a new attractive term in this work. The results of the new modification of CPA EoS were compared with the experimental data of two oil samples (oil samples 1 and 2) that belonged to Moradi et al. The results showed that this modified CPA EoS can predict asphaltene precipitation with good accuracy. [ABSTRACT FROM AUTHOR]

Asphaltene deposition had always been a challenge for the flow assurance issues in oil industry due to both high removal costs and complex behavior in various temperature and composition conditions. These conditions could occur in any enhanced oil recovery (EOR) in the reservoir, and production of oil in tubing or surface facilities. The central composite experimental design of orthogonal type and response surface methodology (RSM) were used to develop reliable models to investigate the effects of input variables on asphaltene onset pressure (AOP). The considered input variables were the temperature and the gas mole% in CO2and N2gas injection scenarios. Regression analysis showed agreement of the experimental data with the determination coefficient (R2) values of 0.991 and 0.987 for CO2and N2gas injection models, respectively. Analysis of variance (ANOVA) was employed to test the significance of the RSM polynomial models. ANOVA study showed, in CO2injection model, the effect of temperature was greater than the gas mole%, while in N2injection model, the gas mole% effect was dominant over the temperature effect. By investigating the models, it was seen that in N2gas injection, any amount of gas increased the AOP at different temperatures. But in CO2gas injection, depending on the temperature, AOP might rise or fall upon adding gas. [ABSTRACT FROM AUTHOR]

Maintaining the flow of multiphase fluid from the reservoir to the surface has been an important issue with wide economic importance for the petroleum industry. Asphaltene precipitation due to change in temperature, pressure, and composition of oil can adversely affect the oil flow to the surface by reducing the available diameter of the tubing. In this study, the precipitation of asphaltene from an Iranian crude oil was investigated. To do our study, through information about asphaltene instability in the live oil during both natural depletion and gas injection conditions about oil sample from Iranian oil field was gathered. Then, the solid model and scaling model were utilized to predict the weight percent of precipitated asphaltene at a wide range of the pressure and temperature. Results of the work revealed that both models predict the increase in weight percent of precipitated asphaltene when lean gas injected to the live oil at the maximum point of asphaltene instability. In addition, the study showed that both models are capable of predicting the experimental data of asphaltene precipitation; while scaling modeling is more reliable when the gas is injected to the oil. [ABSTRACT FROM PUBLISHER]