Air Injection Technique Research Articles

Evaluation of low-temperature oxidation analysis and the development effect of high-pressure air injection in low-permeability reservoirs

In order to solve the problems of conventional water injection development difficulties and low recovery factor in low-permeability reservoirs, the method of high-pressure air drive is adopted to achieve the purpose of reservoir energy enhancement and efficiency improvement. This paper conducted an experimental study on the mechanism of low-temperature oxidation (LTO) for crude oil in the process of high-pressure air flooding, elaborated the relationship between the LTO properties of crude oil and the temperature, pressure, and water saturation of the reservoir, and analyzed the differences in LTO oxygen consumption and oil components under different reaction conditions. In addition, combined with the air flooding physical simulation experiment, the dynamic evolution law of recovery rate in the air flooding process was revealed. Findings from this inquiry indicate that an escalation in the oxidation temperature significantly amplifies the oxygen incorporation reaction within the crude oil matrix. This augmentation in oxidative conditions leads to an uptick in oxygen consumption, which subsequently precipitates a reduction in the lighter fractions of the oxidized oil while enriching its heavier components. Elevated pressures were found to enhance the propensity for the amalgamation of unstable hydrocarbons with oxygen, fostering comprehensive and heterogeneous oxidation reactions. Notably, an excessive presence of water was observed to detrimentally affect the thermal efficacy of crude oil oxidation processes. In the context of low-permeability reservoirs, air injection techniques have emerged as superior in effectuating oil displacement, although an increase in injection pressures has been associated with the phenomenon of gas channeling. Interestingly, adopting a sequential strategy of initiating water flooding before air flooding facilitated the conveyance of high-pressure air via established flushing channels, although it appeared to attenuate the intensity of crude oil oxidation, culminating in an oil recovery efficiency peaking at 51%.

Heat front propagation in shale oil reservoirs during air injection: Experimental and numerical studies

Air injection technique for developing shale oil has gained significant attention. However, the ability of the heat front to consistently propagate within the shale during air injection remains uncertain. To address this, we investigated the heat front propagation within oil–detritus mixtures, shale cores, and fractured shale cores using a self-designed combustion tube (CT) and experimental schemes. By integrating the results obtained from high-pressure differential scanning calorimetry and CT, we developed a comprehensive reaction kinetics model to accurately analyze the main factors influencing the heat front propagation within fractured shale. The findings revealed that in the absence of additional fractures, the heat front failed to propagate within the tight shale. The flow of gases and liquids towards the shale core was impeded, resulting in the formation of a high-pressure zone at the front region of the shale. This pressure buildup significantly hindered air injection, leading to inadequate oxygen supply and the extinguishment of the heat front. However, the study demonstrated the stable propagation of the heat front within the oil–detritus mixtures, indicating the good combustion activity of the shale oil. Furthermore, the heat front successfully propagated within the fractured shale, generating a substantial amount of heat that facilitated the creation of fractures and enhanced gas injection and shale oil flow. It was important to note that after the heat front passed through the shale, the combustion intensity decreased. The simulation results indicated that injecting air into the main fracturing layers of the shale oil reservoir enabled the establishment of a stable heat front. Increasing the reservoir temperature (from 63 to 143 °C) and oxygen concentration in the injected gas (from 11% to 21%) promoted notable heat front propagation and increased the average temperature of the heat front. It was concluded that temperature and oxygen concentration had the most important influence on the heat front propagation, followed by pressure and oil saturation.

Transient Response of Turbocharged Compression Ignition Engine under Different Load Conditions

<div>In urban roads the engine speed and the load vary suddenly and frequently, resulting in increased exhaust emissions. In such operations, the effect of air injection technique to access the transient response of the engine is of great interest. The effectiveness of air injection technique in improving the transient response under speed transient is investigated in detail [<span>1</span>]; however, it is not evaluated for the load transients. Load step demand of the engine is another important event that limits the transient response of the turbocharger. In the present study, response of a heavy-duty turbocharged diesel engine is investigated for different load conditions. Three cases of load transients are considered: constant load, load magnitude variation, and load scheduling. Air injection technique is simulated and after optimization of injection pressure based on orifice diameter, its effect on the transient response is presented. The results reveal that air injection into the intake manifold is an effective technique to improve the turbo lag of a heavy-duty turbocharged diesel engine under the transient conditions of load.</div>

Single-injection caudal thoracic paravertebral block improves pain control and recovery quality in female dogs undergoing unilateral radical mastectomy: a randomized controlled trial.

To test clinical and analgesic effects of a single-injection caudal thoracic paravertebral block (TPVB) after localization of the thoracic paravertebral space with a loss-of-resistance to air injection technique in female dogs undergoing unilateral radical mastectomy. 14 client-owned dogs. Dogs were premedicated with methadone, anesthetized with propofol and sevoflurane, and randomly assigned to receive a TPVB or no block preoperatively. Rescue analgesia with fentanyl and methadone was provided on the basis of cardiovascular responses during surgery and postoperative pain scores assigned with a validated pain scale. Required dose of rescue opioids; mean end-tidal sevoflurane concentration; episodes of hypotension, bradycardia, and other complications; quality of recovery scores; and postoperative pain scores were compared between groups. Median intraoperative fentanyl doses were 0 µg/kg (range, 0 to 2 µg/kg) and 4 µg/kg (range, 2 to 6 µg/kg) for the TPVB and control groups, respectively. Median postoperative methadone doses were 0 mg/kg (range, 0 to 0.2 mg/kg) and 0.6 mg/kg (range, 0.4 to 0.6 mg/kg) for the TPVB and control groups, respectively. Recovery scores and pain scores assigned at the time of and 1 hour after extubation were significantly lower in the TPVB group than in the control group. A single-injection caudal TPVB improved pain control and recovery quality in female dogs undergoing unilateral radical mastectomy. Because the TPVB involves only a single injection, does not take long to perform, and requires only readily available low-cost equipment, the technique may be a valuable option in both referral and first-opinion practice.

Experimental assessment on the explosion pressure of CH4-Air mixtures at flammability limits under high pressure and temperature conditions

High-pressure air injection technique has been extensively used for enhanced oil recovery in oilfields. Yet, it is of great concern on the process safety in terms of the explosion of natural gas-air mixtures. To deeply understand the explosion characteristics in the air injection procedure, explosion experiments for methane (a main component of natural gas) and air mixture were conducted using a cylindrical vessel at elevated pressure and temperature situations. The explosion pressure, the pressure rise rate and deflagration index of CH4 and air mixtures in a closed chamber were investigated under pressure up to 15 MPa and temperature up to 100 °C, and the effect of CH4 concentration on explosion pressure was also examined. The results of this research can provide useful data to quantify the dependency of explosion risk parameters on pressure, temperature and gas concentration. The experimental results indicate that the explosion pressure at flammability limits of CH4 gradually increases with initial pressure, while it can be slightly declined at elevated temperatures. The pressure rise rate and deflagration index increase at high pressures, but these values become lower at higher temperatures. At lower flammability limits and upper flammability limits of CH4-air mixtures, the explosion pressure can be greatly reduced due to the presence of insufficient combustible gas or high content of inerting gas (N2). The explosion pressure data reported in this study can provide guidelines for the prevention and mitigation of explosion disasters in high-pressure air injection process.

Thermal Energy Estimation by In-situ Combustion in An Abandoned Oil Well

A downside of producing oil is that it can never be fully recovered. After the end of a well's life span, the residual oil remaining in the reservoir on average can be over 30%. This residual oil can be extracted using enhanced oil recovery techniques, one of which combusts the oil in the formation where the average reservoir temperature can increase to 400⁰C for light oil and over 600⁰C for heavy oils. This method can become a significant catalyst in solving Pakistan's energy need and increasing power production. This paper aims to estimate the thermal energy production by combusting this residual oil using in-situ combustion by air injection technique. The study deals with the well Kahi-01 located in the upper Indus basin having three formations. The main target is the Hangu formation and its three reservoir blocks. This formation is characterized by its high residual oil percentage of 76-85% at depths of about 1691-1741 meters. The results show that the highest thermal energy output among the three reservoirs was 34.6e6 Megajoules. The highest power output from the binary plant was 38.5e4 Kilowatt hour.

Low temperature oxidation of heavy oil in oxygen-reduced air: Effect of pressure and oxygen content on heat release

Air injection for in situ combustion (ISC) and air injection assisted cyclic steam stimulation (AACSS) techniques have a good application prospective in the development of heavy oils, while the explosion risk in the process of air injection is of great concern and has restricted the application of the technology. So that injection of oxygen-reduced air has been proposed to eliminate and control the explosion of oil/gas mixture with air. In this study, low-temperature oxidation experiments of heavy oil samples were conducted using a small batch reactor under the pressure of 5–15 MPa and oxygen content of 5%–15% at 225 °C in order to investigate the effect of oxygen content and pressure on the reaction rate and heat release during oxidation of heavy oil with oxygen-reduced air. The variations of temperature and pressure during the oxidation reaction were measured in the experiment, and the explosion phenomena of heavy oils were observed in the air with high oxygen contents (oxygen content more than 15%). The reaction rate and the exothermic heat of the reaction were calculated based on the pressure and temperature curves and using an improved heat loss model. The experimental results showed that reducing the oxygen content (e.g. reduced oxygen less than 10%) in air can effectively prevent the explosion of oil-gas mixtures, and the reaction rate and heat release during heavy oil oxidation are linearly proportional to pressure and oxygen content in the injected air when oil is in excess. The results of this study indicate that the heat generated in oil oxidation, which is important for the ISC and AACSS processes, can be controlled by pressure and oxygen content of the injected air, which can lay a good foundation for the oxygen-reduced air injection technique, especially for its application in deep heavy oil reservoirs, in which injection of oxygen-reduced air at high pressure can offset the effect of low oxygen content on heat release.

Femtosecond laser-assisted big bubble for deep anterior lamellar keratoplasty.

To assess the utility of a femtosecond laser-assisted stromal channel to assist the creation of a big bubble (BB) for deep anterior lamellar keratoplasty (DALK) surgery in cadaveric corneas. L V Prasad Eye Institute, Hyderabad, India. Experimental study. An attempt to create a BB was made on 10 donor pairs of human cadaveric corneoscleral tissues. The 20 corneas were split into 2 groups: Group A underwent femtosecond laser pretreatment and Group B had conventional manual deep lamellar technique. Laser pretreatment was performed using the VisuMax femtosecond laser system to create a stromal channel using the intracorneal ring segment treatment module for direct insertion of the 27-gauge air cannula for pneumodissection at a predetermined depth. Of the 20 corneas studied, type 1 BB was achieved in 9 of 10 corneas in Group A and in 7 of 10 corneas in Group B. One cornea from Group A had a combined type 1 and 2 BB, whereas no BB was achieved in 1 cornea. Creation of an intrastromal channel using a femtosecond laser at a predetermined depth seemed to be a promising option to increase the chances of achieving a BB when compared with the conventional air injection technique of BB DALK.

Experimental investigation of heat transfer and exergy loss in heat exchanger with air bubble injection technique

The main aim of this study is to evaluate thermal performance and exergy analysis of a shell-and-tube heat exchanger with a new technique called air bubble injection. The study has been carried out with different parameters such as flow rate, fluid inlet temperature, and different air injection techniques. The air has been injected at different locations such as the inlet of pipe, throughout the pipe, and in the outer pipe of the heat exchanger. Based on the results, the performance of the heat exchanger enhances with an increase in the flow rate and the fluid inlet temperature. The exergy loss and dimensionless exergy loss increase with a rise in the flow rate. The maximum and dimensionless exergy losses are obtained at a maximum flow rate of 3.5 l min−1. With the air bubble injection in the heat exchanger, it has been observed that the temperature difference increases, which leads to an increase in the exergy loss. The injecting air bubbles throughout the tube section shows that minimum dimensionless exergy is 27.49% concerning no air injection.

Experimental studies on reaction laws during the process of air injection into the oil reservoirs with low permeability

The low permeability oil reservoirs are widely distributed in the world, but difficult to develop with the traditional methods due to the low permeability and poor injection properties. Air injection technique not only has the common characteristics of other gas injection techniques, but also can improve the quality of crude oil in situ because of the oxidative ability of the injected air, with a unique advantage in developing low permeability reservoirs. In order to study the reaction regularity between the hydrocarbon components in crude oil under different conditions with the oxygen in the injected air, this experiment is designed for a low permeability sandstone reservoir. In this experiment, one set of self-designed static low-temperature oxidation equipment (including injection pump and high-temperature high–pressure reactor with sampling outlets) has been used. Through analysis of the results of the chromatography for over 60 oil and gas samples, conclusions can be made that after low temperature oxidation (LTO) reactions between the crude oil and the oxygen in the injected air, the concentration of the heavy components in crude oil decreased, and the concentration of the light components increased. By injecting oxygen-reduced air with 8% of oxygen, the concentration of the heavy components of crude oil in the target reservoir reduced most obviously. The formation water and associated gas can hinder the pyrolysis of heavy components, while the minerals in the formation can accelerate the pyrolysis process. The relationship between the carbon atoms number in each of the most consumed hydrocarbon molecule and different LTO reaction conditions has been proposed. According to the sensitivity analysis, it is believed that the influence of the formation water on the LTO reactions is greater than that of minerals in the formation, and influence of associated gas is less than that of minerals. Finally, combined the related physical and chemical theories, a LTO chemical reaction equation has been put forward for the targeted low permeability oil reservoir. The conclusions of the studies can provide some references for the indoor experiments and field applications of air injection in the future.

Optimization of staged combustion in a 600 MWe tangentially fired boiler with wall air injection

Low NOx combustion technology is used in coal-fired boilers to reduce the generation of NOx cost-effectively. However, this technology causes the problem of high temperature corrosion and slagging of water-cooled walls. In this study, a wall air injection technique is presented to effectively alleviate these problems, especially for the low quality coal. The wall air is injected vetically into the furnace to reduce the tangential circle diameter through the nozzles installed on the water wall. In a 600 MWe tangentially fired boiler, the wall air injection technique was retrofitted to study the influences of the wall air velocity and the tangential circle direction on the boiler combustion performance by simulation method. The applicability of the wall air injection technique for the combustion of the design coal and the low quality coal was also studied. The results showed that the wall air velocity of ~ 40 m/s was optimum for the combustion of the low quality coal. The following improvements in the combustion performance were observed at the wall air velocity of 40 m/s: 1) the actual tangential circle diameter was close to the design value of 14 m; 2) the mean flue gas temperature on the water wall decreased by about 600 K while that in the furnace center increased by about 80 K at most; 3) the mean CO mole fraction reduced by about 0.03; and 4) the NOx generation reduced by 38 mg/Nm3. When the wall air injection direction was clockwise, the NOx generation at furnace outlet decreased by 6 mg/Nm3.

Functional anatomy and xylem cavitation resistance of three species of monocotyledons grown on flooded substrates.

There are few investigations that analyze the xylem functional anatomy of monocotyledons, as the methods have been developed for woody plants. This study describes the root, rhizome and aerial stem xylem anatomy and functional anatomy of Canna indica, Cyperus papyrus and Phragmites communis grown on flooded substrates; and it aims to evaluate the relationship between the xylem anatomy and its cavitation resistance. To calculate the indexes of vulnerability, mesomorphy, collapse and relative hydraulic conductivity in the three organs mentioned, the diameter, number of vessels per mm2 , thickness of the walls and the length of the tracheal elements were recorded. In addition, the xylem specific conductivity of the aerial stem was measured with the pipette method, and its resistance to cavitation was determined experimentally by the air injection technique. The protoxylem is xeromorphic, it has longer vessel elements, smaller diameters, thin walls and scalariform perforation plates, whereas the metaxylem is mesomorphic, with shorter vessel elements, larger diameters, thicker walls and simple perforation plates. Both present low collapse resistance but have a high relative hydraulic conductivity. P. communis recorded the highest cavitation resistance, and the number of vessels per mm2 was related to xylem cavitation resistance in Canna indica and Cyperus papyrus. The experimental results of this investigation match partially the anatomical indexes and showed that the xylem of these species has a low specific conductivity and is more vulnerable to cavitation than that of other monocots.

Seismic response of partially saturated soils beneath shallow foundations under sequential ground motions

Induced partial saturation is an innovative soil improvement technique intended to mitigate earthquake-induced liquefaction. Historical records indicate that successive earthquakes may occur in high seismic areas. Therefore, a comprehensive understanding of the response of partially saturated soils to sequential ground motions is of great significance for the rational design and execution of this method in engineering practice. In this study, a series of dynamic centrifuge experiments were conducted to investigate the impacts of sequential ground motions on the behavior of partially saturated soils beneath shallow foundations. Two different shallow foundation models with a bearing pressure of 135 kPa and 50 kPa were examined. Three seismic simulations, in order of increasing amplitudes, were sequentially applied to loosely-packed partially saturated sand models prepared with air injection technique. The assessment of the test results indicated that shallow foundations resting on saturated models of loose sand did suffer excessive settlements with each event, producing a large embedment of the foundation. However, much smaller settlements were recorded for partially saturated ground, and the level of the foundation embedment remained limited in this case. The deformation vector fields also indicated that different displacement mechanisms were observed for each successive event.

Catalytic Effect of Cobalt Additive on the Low Temperature Oxidation Characteristics of Changqing Tight Oil and Its SARA Fractions

Air flooding is a potential enhanced oil recovery (EOR) method to economically and efficiently develop a tight oil reservoir due to its sufficient gas source and low operational costs, during which low temperature oxidation (LTO) is the key to ensuring the success of air flooding. In addition to inefficiency of conventional LTO, air flooding has seen its limited applications due to the prolonged reaction time and safety constraints. In this paper, a novel air injection technique based on the catalyst-activated low temperature oxidation (CLTO) is developed to improve the operational safety together with its oil recovery in tight oil reservoirs. Experimentally, static oxidation experiments are conducted to examine the influence of the catalyst on the LTO reaction kinetics of Changqing tight oil and its fractions. The catalytic oxidation characteristics are identified by applying a thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR) with respect to tight oil and its SARA (i.e., saturates, aromatics, resins, and asphaltenes) fractions. Accordingly, the catalyst can obviously decrease the LTO reaction activation energy of the Changqing tight oil and its SARA fraction. Cobalt additive can change the LTO reaction pathways of the SARA fractions, i.e., promoting the formation of hydroxyl-containing oxides and CO2 from the oxidation of saturates, aromatics and resins, while inhibiting the formation of ethers from the oxidation of aromatics and resins. The LTO of each SARA fraction contains both oxygen addition reaction and bond scission reaction that can be effectively promoted with the cobalt additive. The catalytic effect on the bond scission reaction is continuously enhanced and becomes gradually stronger than that on the oxygen addition reaction as the reaction proceeds.

Performance of a Heavy-Duty Turbocharged Diesel Engine Under the Effect of Air Injection at Intake Manifold During Transient Operations

The effectiveness of an air injection technique for the improvement in transient response of heavy-duty turbocharged diesel engines has been investigated but only to a limited extent. In the present work, the investigations are performed to improve the response characteristic of a heavy-duty turbocharged diesel engine under the transient event of rapid acceleration at low engine speeds. The engine model is developed using Ricardo wave software; and after the validation with the data obtained from the real engine, wave model is used to investigate the effectiveness of an air injection system for the improvement in performance of turbocharged diesel engine. The effect of air injection is observed by varying the air injection pressure and the time of acceleration. The turbocharger’s response parameters such as the compressor exit pressure, turbine inlet temperature and turbine inlet pressure have been monitored to quantify the turbocharger lag. A pressure value of 1 bar is found to be the optimum injection pressure value that significantly reduces the turbocharger lag corresponding to all the selected parameters. Furthermore, faster recovery time is observed for the tests with 1 s duration of acceleration than that with 2 s duration of acceleration. Turbo lag reduction in percentage per unit energy is found to be 29.0%, 39.2% and 55.5% per Joule based on compressor exit pressure, turbine inlet pressure and turbine inlet temperature, respectively, at 1 bar of air injection pressure.

Physical modelling of air injection to remediate liquefaction

Seismic liquefaction of loosely packed, saturated soils poses a significant threat to the built environment. Recently, air injection into liquefiable soil deposits has been introduced as an innovative and cost-effective liquefaction mitigation technique. However, few effective guidelines are available to the engineers for its application and performance. The way that air should be injected appropriately, most particularly, in the presence of structures, is not clearly defined. The distribution of retained air bubbles within the saturated soil medium and its effect on the seismic response also need further investigation. In an effort to offer insights into this problem, an experimental programme consisting of a series of centrifuge and 1g shaking table tests was undertaken. The results have shown that the use of higher air injection pressure provides a much wider and a more uniform air-entrapped zone, but increases the risk of soil deformations developed under the foundations. The distance from the air injector and preferential flow pathways influence the distribution of the retained air bubbles and seismic response of the soil models. Moreover, it was shown in a novel way that the air injection technique is not very effective at low confining stresses to reduce liquefaction-induced deformations beneath shallow foundations.

Durability of partial saturation to counteract liquefaction

Recently, artificially introducing gas/air into liquefiable soils has been presented as a method for reducing the risks from liquefaction. Although this method offers a simple and cheap solution, its use in practical applications is still very limited. This might be primarily ascribed to the concerns of practising engineers about the durability of gas/air bubbles in soils over time. This paper discusses the durability of entrapped air bubbles under various simulated field conditions that may potentially cause the dissolution, diffusion, compression and escape of air bubbles. Multiple series of 1g vertical sand column and high-g centrifuge tests were undertaken to provide insights into the problem. Air-induced partially saturated soils were prepared using an air-injection technique. The test results showed that the majority of entrapped air bubbles in soils can persist under several simulated field conditions for a sufficient period of time, indicating the long-term reliability of the mitigation accomplished.

A new method for identifying the cut ends in canalicular laceration

To locate the proximal and distal cut ends of the canaliculus following trauma is the most difficult part of canalicular repair, especially in patients with complex acute canalicular lacerations and late presenting canalicular lacerations. Previously, irrigation and air-injection technique are reported and widely used to locate the cut ends of lacerated canaliculus. However, we have developed a novel technique in which with a 23 Ga fiber optic light pipe is used to identify the cut ends of the canaliculus allowing silicone tube intubation of the lacrimal system. The mean time from initiation of the identification of the cut ends of the canaliculus to insertion of the silicone tube was 5 minutes. In this study, the cut ends were successfully identified by using this novel method in 33 cases of acute and late presenting canalicular laceration for canalicular reconstruction without any complications. This light-guided technique may represent an improvement in the surgical repair of canalicular lacerations.

Experimental study on the influence of air injection on unsteady cloud cavitating flow dynamics

The main purpose of this study was to investigate the influence of air-injection technique on unsteady cloud cavitating flow dynamics. High-speed camera and pressure measurement system are used to record ventilated cavitation images and wall-pressure fluctuation in a convergent–divergent channel, respectively. The measured ventilated cavitation evolution process and corresponding wall-pressure fluctuation are compared with those obtained under non-ventilation condition. The results show that air-injection technique can significantly suppress pressure pulses induced by cavity collapse. Furthermore, by increasing ventilation rate, the time evolution of cavitation tends to be more stable, the wall-pressure fluctuation magnitude is reduced significantly, and the cloud shedding frequency is reduced, which is believed to be related to the interaction between injected air and re-entrant flow.

Numerical simulation of centrifuge tests to evaluate the performance of desaturation by air injection on liquefiable foundation soil of light structures

Four dynamic centrifuge tests were conducted to study the performance of a newly developed countermeasure technique against soil liquefaction: “desaturation by air injection”. In the experiment, liquefiable foundation soils below lightweight structures were desaturated by the air injection technique and base shaking was imparted to the models to obtain a comprehensive set of response data. In this study, numerical simulations of these experiments were conducted by using a two-phase (solid and fluid) fully coupled finite-element code, Coupled Analysis of Liquefaction (LIQCA-2D), to validate the numerical procedures. The mechanical properties of the soil in the saturated and desaturated zones in the models were exactly the same, with the exception of the degree of saturation. The simulation attempted to examine the desaturated models by changing the compressibility of the pore fluid, in which all input parameters for saturated and desaturated models were the same except for the bulk modulus, Kf. Numerical results were comparable with the test results in terms of excess pore pressures and settlement of structures for both saturated and desaturated models. This validates the numerical procedure and further assures the effectiveness of desaturation by the air injection technique as a liquefaction countermeasure.