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 t...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℃) 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.展开更多
This article experimentally studies the effects of air injection near the blade trailing edge on flow separation and losses in a highly loaded linear compressor cascade. Aerodynamic parameters of eight cascades with d...This article experimentally studies the effects of air injection near the blade trailing edge on flow separation and losses in a highly loaded linear compressor cascade. Aerodynamic parameters of eight cascades with different air injection slot configura- tions are measured by using a five-hole probe at the cascade outlets. Ink-trace flow visualization is performed to obtain the flow details around the air injection slots. The static pressure distribution is clarified with pressure taps on the endwalls. The...展开更多
·AIM:To evaluate the efficacy and safety of full-thickness sutures combined with intracameral air injection(FTS-AI)versus pre-Descemet’s membrane sutures combined with intracameral air injection(PDS-AI)in the ma...·AIM:To evaluate the efficacy and safety of full-thickness sutures combined with intracameral air injection(FTS-AI)versus pre-Descemet’s membrane sutures combined with intracameral air injection(PDS-AI)in the management of acute corneal hydrops in keratoconus.·METHODS:The research included 8 patients(8 eyes)suffering from acute corneal hydrops caused by keratoconus.Four patients were randomly assigned to FTS-AI.And the other four were randomly assigned to PDS-AI.Corneal oedema,visual acuity,corneal thickness were assessed during follow-up.·RESULTS:The demographics,preoperative duration of symptoms and severity of corneal hydrops between the two groups were not significantly different.The mean corneal oedema resolution time after FTS-AI and PDSAI were 11±1.15 and 15±1.41 d,respectively(P=0.005).The maximum corneal thickness of the scarred region decreased in both groups at one week postoperatively(P<0.05).No obvious difference was found in the mean maximal corneal thickness between the two groups postoperatively.The BCVA improved significantly after FTS-AI and PDS-AI at three months postoperatively.No obvious difference was found in the BCVA after FTS-AI and PDS-AI at three months postoperatively.·CONCLUSION:FTS-AI and PDS-AI are safe and effective therapies to accelerate the resolution of corneal oedema in acute corneal hydrops secondary to keratoconus.Despite faster resolution of corneal oedema in the FTS-AI group,we recommend PDS-AI to avoid potential endothelium cell damage.展开更多
The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into fo...The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.展开更多
Steady air injection upstream of the leading edge was used to increase the surge margin of a centrifugal compressor.To reveal the mechanism,steady numerical simulations were performed on a high pressure ratio centrifu...Steady air injection upstream of the leading edge was used to increase the surge margin of a centrifugal compressor.To reveal the mechanism,steady numerical simulations were performed on a high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s.Eight different injection yaw angle with four different injection mass flow was performed to determine the configuration that provide the best results for the compression system studied in this work.The injection angle,α,was fifteen degree and the injectors were placed at short distance（ten percent of the inlet tip radius upstream of the compressor face） to achieve maximum control over the leading edge flow by varying individual injection parameters.The results show that at design speed（n=50 000 r/min） with injection flow rate more than 2% of the main flow rate and yaw angle between 20° and 30°,the mass flow rate at stall decreases for approximately 8%.But with higher injection rate,other compressor parameters were affected such as compressor efficiency and compressor total pressure ratio.展开更多
From a time value of revenue point of view,it is preferred that the time between reservoir stimulation and oil production response is small.Heavy oil combustion processes have a lag time between air injection and liqu...From a time value of revenue point of view,it is preferred that the time between reservoir stimulation and oil production response is small.Heavy oil combustion processes have a lag time between air injection and liquid production,but the common practice in production data analysis uses simultaneous injection and production data when seeking a relationship between them.In this research,the time scales of production for the Kerrobert toe-to-heel air injection(THAI)heavy oil project in Saskatchewan,Canada,is analyzed by using cross correlation analysis,i.e.time delay analysis between air injection and oil production.The results reveal two time scales with respect to production response with two distinctive recovery mechanisms:(1)a short time scale response(nearly instantaneous)where oil production peaks right after air injection(directly after opening production well)reflecting cold heavy oil production mechanisms,and(2)a longer time scale(of order of 100-300 days)response where peak production occurs associated with the collective phenomena of air injection,heat generating reactions,heat transfer,and finally,heated mobilized heavy oil drainage to the production well.This understanding of the two time scales and associated production mechanisms provides a basis for improving the performance of THAI.展开更多
Cutter-suction dredger transports slurry through pipeline. But the pipeline is easy to be jammed and frayed because of huge resistance, resulting in limited exertion of dredger and high energy consumption. One of the ...Cutter-suction dredger transports slurry through pipeline. But the pipeline is easy to be jammed and frayed because of huge resistance, resulting in limited exertion of dredger and high energy consumption. One of the solutions is air injection transporting, which can reduce the resistance in pipeline. This paper makes research on the relations between pipeline distance and other factors such as slurry concentration, pressure of air injection and transportation distance, by making use of Prof. Aluf Orell＇ s slug model. The test data prove that the key factors are slurry concentration and air volume fraction, and that high slurry concentration and low air volume fraction can reduce more resistance, and such reducing effect becomes weaker with the increase of transportation distance.展开更多
Because of the nature of low permeability of shale and tight reservoirs,a gas injection method has the advantage of enhancing oil recovery.Among gases,air has its vast and free resources.And one extra benefit is its t...Because of the nature of low permeability of shale and tight reservoirs,a gas injection method has the advantage of enhancing oil recovery.Among gases,air has its vast and free resources.And one extra benefit is its thermal effect resulting from combustion.However,issues of feasibility of spontaneous ignition,oil requirement,and air requirement for the continuation of combustion in shale and tight reservoirs need to be addressed.This paper is to address these issues with the aid of numerical simu lation.The relevant literature information is reviewed when discussing these issues.It is found that failure of spontaneous ignition may be caused by more factors such as vaporization,fuel displacement by air,etc.,in addition to lack of oil exothermicity and heat loss that are commonly believed;the oil saturation difference between the initial oil saturation and the remaining oil saturation after air flooding and low-temperature oxidation is proposed to define the oil content;air requirement may not be satisfied in typical shale or tight reservoirs because of the low injectivity.More factors can complicate the issues of feasibility of spontaneous ignition,oil requirement,and air requirement.Therefore,a simulation approach is more appropriate to address those issues.展开更多
This article addresses the corrosion problem of P110 tubing during the process of enhancing oil recovery by injecting air.The effects of changes in oxygen content and tensile stress on the corrosion of P110 tubing wer...This article addresses the corrosion problem of P110 tubing during the process of enhancing oil recovery by injecting air.The effects of changes in oxygen content and tensile stress on the corrosion of P110 tubing were studied using electrochemical testing methods.The results show that with an increase in oxygen content(0,10000 ppm,20000 ppm,30000 ppm,40000 ppm),the product film on the surface of P110 tubing is loose and porous,the film resistance and charge transfer resistance decrease,the selfcorrosion current density increases,and the corrosion intensifies.With an increase in tensile stress(0,20%Ϭs,50%Ϭs,70%Ϭs,100%Ϭs),the corrosion tendency of P110 tubing increases,the stability and protection of the product film are destroyed,the film resistance and charge transfer resistance decrease,the electrochemical activity of the steel surface increases,the self-corrosion current density increases,and the corrosion intensifies.Based on this,considering the effects of oxygen content and tensile stress on the corrosion of P110 tubing,anti-corrosion suggestions are given to provide a reference basis for corrosion control of air-injected tubular columns.展开更多
The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of a...The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of air injection.In this study,the tight shale sample underwent oxidation at various LTO temperatures,followed by an analysis of the resulting gas composition.Furthermore,the oxidized oil was separated from the tight shale and subjected to characte rization using electron paramagnetic resonance,nuclear magnetic resonance,and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry techniques.The primary focus was on examining the distinct LTO reaction pathways observable across different temperature ranges.The findings demonstrated a correlation between LTO temperature and the concentration of free radicals,which predominantly resided on aromatic hydrocarbons,alkanes,and oxygen atoms.Additionally,the proton count of polycyclic aromatic hydrocarbons exhibited a continuous increase from 83 to 350℃,suggesting intensified aromatization and condensation reactions involving aliphatic and aromatic compounds.With rising LTO temperature,the molecular structure of O2compounds underwent significant transformations,characterized by increased condensation degree and a decrease in low carbon nu mber molecular structu res,while higher equivale nt double bonds and carbon number molecular structures became more prevalent.The LTO reaction pathways of shale oil included cycle paths 1,2,and 3.The influence of cycle path 1 diminished at temperatures ranging from 83 to 150℃ and 250 to 350℃ whereas the significance of cycle paths 2 and 3 increased,resulting in an overall escalation of the oxidation rate with temperature elevation.It was observed that the shale oil LTO process exhibited a negative temperature coefficient within the temperature range of150 to 250℃,emphasizing the criticality of overcoming the energy barrier in this region to achieve stable combustion.This comprehensive investigation provides valuable insights into the mechanisms underlying LTO in crude oil confined within tight shale.展开更多
Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing...Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing.Air injections are a good strategy for enhancing the thermal performance of the DPHE.In the present work,the influence of air bubble injection in a DPHE was experimentally investigated,and the system’s hydrothermal performance improvement parameters were evaluated.Two modes were designed,manufactured,and used to conduct the experiments.The first mode was conducted with no air injection,named a single phase mode,while in the second mode,air was injected into the annulus of DPHE throughout different perforated rings on the side of the annular.Three different ring types were used and coded as R-1,R-2,and R-3,with an added case of insertion of the three rings inside the annulus.The airflow rate was fixed at 1.5 LPM with a 25○C inlet temperature.Also,the hot water rate in the inner pipe was maintained continuously at 3 LPM with a controlled 70○C temperature at the inlet.Five different cold water flow rates,3,3.5,4,4.5,and 5 LPM,in the annulus,were considered with a controlled inlet temperature at 17○C.Additionally,the effectiveness of the heat exchanger,the number of transfer units(NTU),and the overall heat transfer were predicted and considered for performance evaluation and comparison.The outcomes proved that the injection of air and the bubbly flow creation in the heat exchanger’s hot side is an effective method to strengthen the DPHE performance.Moreover,the total heat transfer coefficient was enhanced by 41%in R-1,58.8%in R-2,and 40.1%in R-3 at 4 LPM of cold water.The optimal ring,which yielded the most improvement,was R-2,achieving a 65%improvement in NTU,with a maximum enhancement in effectiveness of 56%.展开更多
Steady discrete micro air injection at the tip region in front of the first compressor rotor has been proved to be an effective method to delay the inception of rotating stall in a low speed axial compressor. Consider...Steady discrete micro air injection at the tip region in front of the first compressor rotor has been proved to be an effective method to delay the inception of rotating stall in a low speed axial compressor. Considering the practical application a new type of micro injector was designed and described in this paper, which was imbedded in the casing and could be moved along the chord. In order to verify its feasibility to other cases, such as high subsonic axial compressor or centrifugal compressor, some other cases have been studied. Experimental results of the same low speed axial compressor showed that the new injector could possess many other advantages besides successfully stabilizing the compressor. Experiments performed on a high subsonic axial compressor confirmed the effectiveness of micro air injection when the relative velocity at the blade tip is high subsonic. Meanwhile in order to explore its feasibility in centrifugal compressor, a similar micro injector was designed and tested on a low speed centrifugal compressor with vaned diffuser. The injected mass flow was a bit larger than that used in axial compressors and the results showed micro injection could also delay the onset of rotating stall in the centrifugal compressor.展开更多
Cavitation commonly induces performance deterioration and system vibration in many engineering applications.This paper aims to investigate the effects of air injection on cavitation evolution,pressure pulsation and vi...Cavitation commonly induces performance deterioration and system vibration in many engineering applications.This paper aims to investigate the effects of air injection on cavitation evolution,pressure pulsation and vibration in a centrifugal pump with inducer.In this paper,the high-speed camera is used to capture the gas flow pattern and cavitation evolution process in the inducer.The impacts of air injection on the inlet pressure pulsation and vibration are also investigated.The results show that the cavitation development in the inducer undergoes four patterns:incipient cavitation,sheet cavitation,cloud cavitation and super cavitation.During the development of cavitation,the main frequency of the pressure pulsation shifts to lower frequencies,and the amplitude of the vibration increases.In addition,air injection promotes the incipient cavitation but delays the cavitation development.A small amount of air can effectively decrease amplitudes of pressure pulsation and vibration.But as the air content increases,the fluctuations and amplitudes of pressure pulsation and vibration increase.展开更多
The aim of this study is to reveal the influence mechanism of endwall air injection with distributed holes on the corner separation of a highly loaded compressor cascade,so as to promote the application of injection i...The aim of this study is to reveal the influence mechanism of endwall air injection with distributed holes on the corner separation of a highly loaded compressor cascade,so as to promote the application of injection in aero-engines.Single-hole and double-hole endwall injection schemes featuring different axial locations,pitchwise locations,injection mass rates and injection directions,were designed and investigated.Results showed that the corner separation was eliminated by endwall injection;the optimal single-hole injection scheme achieved an endwall loss coefficient reduction of 29.7%,with injection coefficient as low as 0.48%.The optimal axial location of single-hole endwall injection was at 82%axial chord,being the center of corner separation.However,as injection hole was located at upstream of it,endwall injection resulted in severer corner separation.The mid-span flow field was deteriorated after endwall injection,which was due to 3D flow effects,i.e.,AVDR(axial velocity density ratio)effect and low-momentum fluid spanwise migration effect.The optimal injection was achieved at low injection angle and from close to the suction surface on pitchwise.Double-hole injection exhibited inferior performance compared with single-hole,which was due to the interaction of the two injection streams and mixing of injection streams with the bulk stream.展开更多
This paper is the first attempt to evaluate huff-n-puff air injection in a shale oil reservoir using a simulation approach.Recovery mechanisms and physical processes of huff-n-puff air injection in a shale oil reservo...This paper is the first attempt to evaluate huff-n-puff air injection in a shale oil reservoir using a simulation approach.Recovery mechanisms and physical processes of huff-n-puff air injection in a shale oil reservoir are investigated through investigating production performance,thermal behavior,reservoir pressure and fluid saturation features.Air flooding is used as the basic case for a comparative study.The simulation study suggests that thermal drive is the main recovery mechanism for huff-n-puff air injection in the shale oil reservoir,but not for simple air flooding.The synergic recovery mechanism of air flooding in conventional light oil reservoirs can be replicated in shale oil reservoirs by using air huff-npuff injection strategy.Reducing huff-n-puff time is better for performing the synergic recovery mechanism of air injection.O2 diffusion plays an important role in huff-n-puff air injection in shale oil reservoirs.Pressure transmissibility as well as reservoir pressure maintenance ability in huff-n-puff air injection is more pronounced than the simple air flooding after primary depletion stage.No obvious gas override is exhibited in both air flooding and air huff-n-puff injection scenarios in shale reservoirs.Huffn-puff air injection has great potential to develop shale oil reservoirs.The results from this work may stimulate further investigations.展开更多
In this work, we perform a numerical study of a water flow over a stepped spillway. This flow is described by the Reynolds averaged Navier-Stokes equation （RANS） associated with the turbulence k - model. These equat...In this work, we perform a numerical study of a water flow over a stepped spillway. This flow is described by the Reynolds averaged Navier-Stokes equation （RANS） associated with the turbulence k - model. These equations are solved using a commercial software based on the finite volume scheme and an unstructured mesh. The air-water flow was modeled using volume of fluid （VOF） and multiphasic methods. The characteristics of the profile, etc.. We analyze the effects on the flow structure of the flow were investigated including the total pressure, the velocity steps and countermarch inclination, the air injection through the countermarch into the water flow and the dynamics water discharges. Results show that the inclination of the countermarch relative to the vertical and the air injection into the water flow increase the total pressure in the neighbourhood of the steps.展开更多
Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on ...Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on the University of Florida scramjet experimental facility.Turbulence was modeled using k-u shear stress transport(SST),laminar flamelet was used for combustion modeling.Wall static pressure showed good agreement with experimental data for non-reacting and reacting flow.For non-reacting flow,dummy fuel helium mole fraction distribution in the recirculation region behind the step was validated with planar laser induced fluorescence(PLIF)images in experiments.To improve the combustion characteristics,air was injected in tandem with hydrogen at step base using various configurations.With all fuel injection as baseline,the case with 2 air jets around each fuel jet and air injected at 2 times the stagnation pressure of fuel showed the most improvement compared to other cases.It was most effective in reducing the local fuel richness,shortening the flame length and increasing combustion efficiency.展开更多
A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer gases.Expe...A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer gases.Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m.The effects of superficial velocity,SA ratio,bed inventory,and particle diameter on the SA mixing were investigated.The results indicate that there are some differences in the measurement results obtained using different tracer gases,wherein the deviation between CO and CO_(2) ranges from 42%to 66%and that between O_(2) and CO_(2) ranges from 45%to 71%in the lower part of the fluidized bed.However,these differences became less pronounced as the bed height increased.Besides,the high solid concentration and fine particle diameter in the CFB may weaken the difference.The measurement results of different tracer gases show the same trends under the variation of operating parameters.Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA.The effect of bed inventory on SA mixing is not monotonic.展开更多
Air injection is a good option to development light oil reservoir.As well-known that,reservoir heterogeneity has great effect for various EOR processes.This also applies to air injection.However,oil recovery mechanism...Air injection is a good option to development light oil reservoir.As well-known that,reservoir heterogeneity has great effect for various EOR processes.This also applies to air injection.However,oil recovery mechanisms and physical processes for air injection in heterogeneous reservoir with dip angle are still not well understood.The reported setting of reservoir heterogeneous for physical model or simulation model of air injection only simply uses different-layer permeability of porous media.In practice,reservoir heterogeneity follows the principle of geostatistics.How much of contrast in permeability actually challenges the air injection in light oil reservoir?This should be investigated by using layered porous medial settings of the classical Dykstra-Parsons style.Unfortunately,there has been no work addressing this issue for air injection in light oil reservoir.In this paper,Reservoir heterogeneity is quantified based on the use of different reservoir permeability distribution according to classical Dykstra-Parsons coefficients method.The aim of this work is to investigate the effect of reservoir heterogeneity on physical process and production performance of air injection in light oil reservoir through numerical reservoir simulation approach.The basic model is calibrated based on previous study.Total eleven pseudo compounders are included in this model and ten complexity of reactions are proposed to achieve the reaction scheme.Results show that oil recovery factor is decreased with the increasing of reservoir heterogeneity both for air and N2 injection from updip location,which is against the working behavior of air injection from updip location.Reservoir heterogeneity sometimes can act as positive effect to improve sweep efficiency as well as enhance production performance for air injection.High O2 content air injection can benefit oil recovery factor,also lead to early O2 breakthrough in heterogeneous reservoir.Well-type does not show great effect on production performance for air injection in extreme heterogeneous reservoir.While adopting horizontal producer is favourable to promote production performance for air injection in homogenous reservoir.展开更多
During air injection into an oil reservoir,an oxidation reaction generates some heat to raise the reservoir temperature.When the reservoir temperature reaches an ignition temperature,spontaneous ignition occurs.There ...During air injection into an oil reservoir,an oxidation reaction generates some heat to raise the reservoir temperature.When the reservoir temperature reaches an ignition temperature,spontaneous ignition occurs.There is a time delay from the injection to ignition.There are mixed results regarding the feasibility of spontaneous ignition in real-field projects and in laboratory experiments.No analytical model is available in the literature to estimate the oxidation time required to reach spontaneous ignition with heat loss.This paper discusses the feasibility of spontaneous ignition from theoretical points and experimental and field project observations.An analytical model considering heat loss is proposed.Analytical models with and without heat loss investigate the factors that affect spontaneous ignition.Based on the discussion and investigations,we find that it is more difficult for spontaneous ignition to occur in laboratory experiments than in oil reservoirs;spontaneous ignition is strongly affected by the initial reservoir temperature,oil activity,and heat loss;spontaneous ignition is only possible when the initial reservoir temperature is high,the oil oxidation rate is high,and the heat loss is low.展开更多
基金supported by National Natural Science Foundation of China (No. 52204049)Natural Science Foundation of Sichuan Province (No. 2024NSFSC0960)Ministry of Science and Higher Education of the Russian Federation under Agreement No. 075-15-2022-299 within the Framework of the Development Program for a World-Class Research Center “Efficient development of the global liquid hydrocarbon reserves”。
文摘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℃) 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.
基金National Natural Science Foundation of China (50876023)Chinese Specialized Research Fund for the Doctoral Pro-gram of Higher Education (20060213007)National Basic Research Program of China (2007CB210100)
文摘This article experimentally studies the effects of air injection near the blade trailing edge on flow separation and losses in a highly loaded linear compressor cascade. Aerodynamic parameters of eight cascades with different air injection slot configura- tions are measured by using a five-hole probe at the cascade outlets. Ink-trace flow visualization is performed to obtain the flow details around the air injection slots. The static pressure distribution is clarified with pressure taps on the endwalls. The...
基金Supported by the National Natural Science Foundation of China(No.82070920)Major Clinical Research Projects of the Three-Year Action Plan for Promoting Clinical Skills and Clinical Innovation in Municipal Hospitals(No.SHDC2020CR1043B-010)。
文摘·AIM:To evaluate the efficacy and safety of full-thickness sutures combined with intracameral air injection(FTS-AI)versus pre-Descemet’s membrane sutures combined with intracameral air injection(PDS-AI)in the management of acute corneal hydrops in keratoconus.·METHODS:The research included 8 patients(8 eyes)suffering from acute corneal hydrops caused by keratoconus.Four patients were randomly assigned to FTS-AI.And the other four were randomly assigned to PDS-AI.Corneal oedema,visual acuity,corneal thickness were assessed during follow-up.·RESULTS:The demographics,preoperative duration of symptoms and severity of corneal hydrops between the two groups were not significantly different.The mean corneal oedema resolution time after FTS-AI and PDSAI were 11±1.15 and 15±1.41 d,respectively(P=0.005).The maximum corneal thickness of the scarred region decreased in both groups at one week postoperatively(P<0.05).No obvious difference was found in the mean maximal corneal thickness between the two groups postoperatively.The BCVA improved significantly after FTS-AI and PDS-AI at three months postoperatively.No obvious difference was found in the BCVA after FTS-AI and PDS-AI at three months postoperatively.·CONCLUSION:FTS-AI and PDS-AI are safe and effective therapies to accelerate the resolution of corneal oedema in acute corneal hydrops secondary to keratoconus.Despite faster resolution of corneal oedema in the FTS-AI group,we recommend PDS-AI to avoid potential endothelium cell damage.
文摘The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.
基金Supported by Chinese Specialized Research Fund for the Doctoral Program of Higher Education (20091101110014)the National Natural Science Foundation of China (51176013)National High Technology Research and Development Program of China("863" Program) (2007AA050502)
文摘Steady air injection upstream of the leading edge was used to increase the surge margin of a centrifugal compressor.To reveal the mechanism,steady numerical simulations were performed on a high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s.Eight different injection yaw angle with four different injection mass flow was performed to determine the configuration that provide the best results for the compression system studied in this work.The injection angle,α,was fifteen degree and the injectors were placed at short distance（ten percent of the inlet tip radius upstream of the compressor face） to achieve maximum control over the leading edge flow by varying individual injection parameters.The results show that at design speed（n=50 000 r/min） with injection flow rate more than 2% of the main flow rate and yaw angle between 20° and 30°,the mass flow rate at stall decreases for approximately 8%.But with higher injection rate,other compressor parameters were affected such as compressor efficiency and compressor total pressure ratio.
基金support from the Department of Chemical and Petroleum Engineering at the University of Calgary,the University of Calgary’s Canada First Research Excellence Fund program(the Global Research Initiative for Sustainable Low-Carbon Unconventional Resources)
文摘From a time value of revenue point of view,it is preferred that the time between reservoir stimulation and oil production response is small.Heavy oil combustion processes have a lag time between air injection and liquid production,but the common practice in production data analysis uses simultaneous injection and production data when seeking a relationship between them.In this research,the time scales of production for the Kerrobert toe-to-heel air injection(THAI)heavy oil project in Saskatchewan,Canada,is analyzed by using cross correlation analysis,i.e.time delay analysis between air injection and oil production.The results reveal two time scales with respect to production response with two distinctive recovery mechanisms:(1)a short time scale response(nearly instantaneous)where oil production peaks right after air injection(directly after opening production well)reflecting cold heavy oil production mechanisms,and(2)a longer time scale(of order of 100-300 days)response where peak production occurs associated with the collective phenomena of air injection,heat generating reactions,heat transfer,and finally,heated mobilized heavy oil drainage to the production well.This understanding of the two time scales and associated production mechanisms provides a basis for improving the performance of THAI.
文摘Cutter-suction dredger transports slurry through pipeline. But the pipeline is easy to be jammed and frayed because of huge resistance, resulting in limited exertion of dredger and high energy consumption. One of the solutions is air injection transporting, which can reduce the resistance in pipeline. This paper makes research on the relations between pipeline distance and other factors such as slurry concentration, pressure of air injection and transportation distance, by making use of Prof. Aluf Orell＇ s slug model. The test data prove that the key factors are slurry concentration and air volume fraction, and that high slurry concentration and low air volume fraction can reduce more resistance, and such reducing effect becomes weaker with the increase of transportation distance.
基金supported by the National Natural Science Foundation of China(No.51974334)the CNPC Innovation Found(Grant No.2021DQ02-0202)+1 种基金the Local Univer sities Reform and Development Personnel Training projects from the Central Authoritiesthe Studyon nanosystemdisplacement method of tight reservoir in Daqing Oilfield.
文摘Because of the nature of low permeability of shale and tight reservoirs,a gas injection method has the advantage of enhancing oil recovery.Among gases,air has its vast and free resources.And one extra benefit is its thermal effect resulting from combustion.However,issues of feasibility of spontaneous ignition,oil requirement,and air requirement for the continuation of combustion in shale and tight reservoirs need to be addressed.This paper is to address these issues with the aid of numerical simu lation.The relevant literature information is reviewed when discussing these issues.It is found that failure of spontaneous ignition may be caused by more factors such as vaporization,fuel displacement by air,etc.,in addition to lack of oil exothermicity and heat loss that are commonly believed;the oil saturation difference between the initial oil saturation and the remaining oil saturation after air flooding and low-temperature oxidation is proposed to define the oil content;air requirement may not be satisfied in typical shale or tight reservoirs because of the low injectivity.More factors can complicate the issues of feasibility of spontaneous ignition,oil requirement,and air requirement.Therefore,a simulation approach is more appropriate to address those issues.
基金support from National Natural Science Foundation of China(No.51774249)supported by Sichuan Science and Technology Program(21JCQN0066).
文摘This article addresses the corrosion problem of P110 tubing during the process of enhancing oil recovery by injecting air.The effects of changes in oxygen content and tensile stress on the corrosion of P110 tubing were studied using electrochemical testing methods.The results show that with an increase in oxygen content(0,10000 ppm,20000 ppm,30000 ppm,40000 ppm),the product film on the surface of P110 tubing is loose and porous,the film resistance and charge transfer resistance decrease,the selfcorrosion current density increases,and the corrosion intensifies.With an increase in tensile stress(0,20%Ϭs,50%Ϭs,70%Ϭs,100%Ϭs),the corrosion tendency of P110 tubing increases,the stability and protection of the product film are destroyed,the film resistance and charge transfer resistance decrease,the electrochemical activity of the steel surface increases,the self-corrosion current density increases,and the corrosion intensifies.Based on this,considering the effects of oxygen content and tensile stress on the corrosion of P110 tubing,anti-corrosion suggestions are given to provide a reference basis for corrosion control of air-injected tubular columns.
基金supported by National Natural Science Founda tion of China(No.52204049)Open Fund(PLN020-23)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)Ministry of Science and Higher Education of the Russian Federation under Agreement No.075-15-2022-299 within the framework of the development pro gram for a world-class Research Center“Efficient development of the global liquid hydrocarbon reserves”.
文摘The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of air injection.In this study,the tight shale sample underwent oxidation at various LTO temperatures,followed by an analysis of the resulting gas composition.Furthermore,the oxidized oil was separated from the tight shale and subjected to characte rization using electron paramagnetic resonance,nuclear magnetic resonance,and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry techniques.The primary focus was on examining the distinct LTO reaction pathways observable across different temperature ranges.The findings demonstrated a correlation between LTO temperature and the concentration of free radicals,which predominantly resided on aromatic hydrocarbons,alkanes,and oxygen atoms.Additionally,the proton count of polycyclic aromatic hydrocarbons exhibited a continuous increase from 83 to 350℃,suggesting intensified aromatization and condensation reactions involving aliphatic and aromatic compounds.With rising LTO temperature,the molecular structure of O2compounds underwent significant transformations,characterized by increased condensation degree and a decrease in low carbon nu mber molecular structu res,while higher equivale nt double bonds and carbon number molecular structures became more prevalent.The LTO reaction pathways of shale oil included cycle paths 1,2,and 3.The influence of cycle path 1 diminished at temperatures ranging from 83 to 150℃ and 250 to 350℃ whereas the significance of cycle paths 2 and 3 increased,resulting in an overall escalation of the oxidation rate with temperature elevation.It was observed that the shale oil LTO process exhibited a negative temperature coefficient within the temperature range of150 to 250℃,emphasizing the criticality of overcoming the energy barrier in this region to achieve stable combustion.This comprehensive investigation provides valuable insights into the mechanisms underlying LTO in crude oil confined within tight shale.
文摘Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing.Air injections are a good strategy for enhancing the thermal performance of the DPHE.In the present work,the influence of air bubble injection in a DPHE was experimentally investigated,and the system’s hydrothermal performance improvement parameters were evaluated.Two modes were designed,manufactured,and used to conduct the experiments.The first mode was conducted with no air injection,named a single phase mode,while in the second mode,air was injected into the annulus of DPHE throughout different perforated rings on the side of the annular.Three different ring types were used and coded as R-1,R-2,and R-3,with an added case of insertion of the three rings inside the annulus.The airflow rate was fixed at 1.5 LPM with a 25○C inlet temperature.Also,the hot water rate in the inner pipe was maintained continuously at 3 LPM with a controlled 70○C temperature at the inlet.Five different cold water flow rates,3,3.5,4,4.5,and 5 LPM,in the annulus,were considered with a controlled inlet temperature at 17○C.Additionally,the effectiveness of the heat exchanger,the number of transfer units(NTU),and the overall heat transfer were predicted and considered for performance evaluation and comparison.The outcomes proved that the injection of air and the bubbly flow creation in the heat exchanger’s hot side is an effective method to strengthen the DPHE performance.Moreover,the total heat transfer coefficient was enhanced by 41%in R-1,58.8%in R-2,and 40.1%in R-3 at 4 LPM of cold water.The optimal ring,which yielded the most improvement,was R-2,achieving a 65%improvement in NTU,with a maximum enhancement in effectiveness of 56%.
基金National Natural Science Foundation of China with project No.50676094.
文摘Steady discrete micro air injection at the tip region in front of the first compressor rotor has been proved to be an effective method to delay the inception of rotating stall in a low speed axial compressor. Considering the practical application a new type of micro injector was designed and described in this paper, which was imbedded in the casing and could be moved along the chord. In order to verify its feasibility to other cases, such as high subsonic axial compressor or centrifugal compressor, some other cases have been studied. Experimental results of the same low speed axial compressor showed that the new injector could possess many other advantages besides successfully stabilizing the compressor. Experiments performed on a high subsonic axial compressor confirmed the effectiveness of micro air injection when the relative velocity at the blade tip is high subsonic. Meanwhile in order to explore its feasibility in centrifugal compressor, a similar micro injector was designed and tested on a low speed centrifugal compressor with vaned diffuser. The injected mass flow was a bit larger than that used in axial compressors and the results showed micro injection could also delay the onset of rotating stall in the centrifugal compressor.
基金supported by the National Natural Science Foundation of China(Grant No.51979126).
文摘Cavitation commonly induces performance deterioration and system vibration in many engineering applications.This paper aims to investigate the effects of air injection on cavitation evolution,pressure pulsation and vibration in a centrifugal pump with inducer.In this paper,the high-speed camera is used to capture the gas flow pattern and cavitation evolution process in the inducer.The impacts of air injection on the inlet pressure pulsation and vibration are also investigated.The results show that the cavitation development in the inducer undergoes four patterns:incipient cavitation,sheet cavitation,cloud cavitation and super cavitation.During the development of cavitation,the main frequency of the pressure pulsation shifts to lower frequencies,and the amplitude of the vibration increases.In addition,air injection promotes the incipient cavitation but delays the cavitation development.A small amount of air can effectively decrease amplitudes of pressure pulsation and vibration.But as the air content increases,the fluctuations and amplitudes of pressure pulsation and vibration increase.
基金This work was sponsored by the seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University(No.CX2020138)National Natural Science Foundation of China(Nos.51806174 and 51741601)the Fundamental Research Funds for the Central Universities of China(No.G2018KY0303).
文摘The aim of this study is to reveal the influence mechanism of endwall air injection with distributed holes on the corner separation of a highly loaded compressor cascade,so as to promote the application of injection in aero-engines.Single-hole and double-hole endwall injection schemes featuring different axial locations,pitchwise locations,injection mass rates and injection directions,were designed and investigated.Results showed that the corner separation was eliminated by endwall injection;the optimal single-hole injection scheme achieved an endwall loss coefficient reduction of 29.7%,with injection coefficient as low as 0.48%.The optimal axial location of single-hole endwall injection was at 82%axial chord,being the center of corner separation.However,as injection hole was located at upstream of it,endwall injection resulted in severer corner separation.The mid-span flow field was deteriorated after endwall injection,which was due to 3D flow effects,i.e.,AVDR(axial velocity density ratio)effect and low-momentum fluid spanwise migration effect.The optimal injection was achieved at low injection angle and from close to the suction surface on pitchwise.Double-hole injection exhibited inferior performance compared with single-hole,which was due to the interaction of the two injection streams and mixing of injection streams with the bulk stream.
基金The authors would like to acknowledge the funding from U.S.Department of Energy under Award Number DE-FE0024311In addition,this paper was supported by National Natural Science Foundation of China(No.51404202)+1 种基金Sichuan Youth Science and Technology Fund(No.2015JQ0038)scientific research starting project of SWPU(No.2014QHZ001).
文摘This paper is the first attempt to evaluate huff-n-puff air injection in a shale oil reservoir using a simulation approach.Recovery mechanisms and physical processes of huff-n-puff air injection in a shale oil reservoir are investigated through investigating production performance,thermal behavior,reservoir pressure and fluid saturation features.Air flooding is used as the basic case for a comparative study.The simulation study suggests that thermal drive is the main recovery mechanism for huff-n-puff air injection in the shale oil reservoir,but not for simple air flooding.The synergic recovery mechanism of air flooding in conventional light oil reservoirs can be replicated in shale oil reservoirs by using air huff-npuff injection strategy.Reducing huff-n-puff time is better for performing the synergic recovery mechanism of air injection.O2 diffusion plays an important role in huff-n-puff air injection in shale oil reservoirs.Pressure transmissibility as well as reservoir pressure maintenance ability in huff-n-puff air injection is more pronounced than the simple air flooding after primary depletion stage.No obvious gas override is exhibited in both air flooding and air huff-n-puff injection scenarios in shale reservoirs.Huffn-puff air injection has great potential to develop shale oil reservoirs.The results from this work may stimulate further investigations.
基金the ERASMUS MUNDUS AVERROES Program,for the financial support off this study
文摘In this work, we perform a numerical study of a water flow over a stepped spillway. This flow is described by the Reynolds averaged Navier-Stokes equation （RANS） associated with the turbulence k - model. These equations are solved using a commercial software based on the finite volume scheme and an unstructured mesh. The air-water flow was modeled using volume of fluid （VOF） and multiphasic methods. The characteristics of the profile, etc.. We analyze the effects on the flow structure of the flow were investigated including the total pressure, the velocity steps and countermarch inclination, the air injection through the countermarch into the water flow and the dynamics water discharges. Results show that the inclination of the countermarch relative to the vertical and the air injection into the water flow increase the total pressure in the neighbourhood of the steps.
文摘Numerical simulations were performed to model the non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base.The combustor geometry was based on the University of Florida scramjet experimental facility.Turbulence was modeled using k-u shear stress transport(SST),laminar flamelet was used for combustion modeling.Wall static pressure showed good agreement with experimental data for non-reacting and reacting flow.For non-reacting flow,dummy fuel helium mole fraction distribution in the recirculation region behind the step was validated with planar laser induced fluorescence(PLIF)images in experiments.To improve the combustion characteristics,air was injected in tandem with hydrogen at step base using various configurations.With all fuel injection as baseline,the case with 2 air jets around each fuel jet and air injected at 2 times the stagnation pressure of fuel showed the most improvement compared to other cases.It was most effective in reducing the local fuel richness,shortening the flame length and increasing combustion efficiency.
基金the Key Project of the National Research Program of China(2020YFB0606201)。
文摘A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer gases.Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m.The effects of superficial velocity,SA ratio,bed inventory,and particle diameter on the SA mixing were investigated.The results indicate that there are some differences in the measurement results obtained using different tracer gases,wherein the deviation between CO and CO_(2) ranges from 42%to 66%and that between O_(2) and CO_(2) ranges from 45%to 71%in the lower part of the fluidized bed.However,these differences became less pronounced as the bed height increased.Besides,the high solid concentration and fine particle diameter in the CFB may weaken the difference.The measurement results of different tracer gases show the same trends under the variation of operating parameters.Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA.The effect of bed inventory on SA mixing is not monotonic.
基金This work is supported by the fund of National Science Foundation of China(Award No.51404202)Sichuan Youth Science and Technology Fund(Award No.2015JQ0038)PetroChina Innovation Foundation(Award No.2017D-5007-0202).
文摘Air injection is a good option to development light oil reservoir.As well-known that,reservoir heterogeneity has great effect for various EOR processes.This also applies to air injection.However,oil recovery mechanisms and physical processes for air injection in heterogeneous reservoir with dip angle are still not well understood.The reported setting of reservoir heterogeneous for physical model or simulation model of air injection only simply uses different-layer permeability of porous media.In practice,reservoir heterogeneity follows the principle of geostatistics.How much of contrast in permeability actually challenges the air injection in light oil reservoir?This should be investigated by using layered porous medial settings of the classical Dykstra-Parsons style.Unfortunately,there has been no work addressing this issue for air injection in light oil reservoir.In this paper,Reservoir heterogeneity is quantified based on the use of different reservoir permeability distribution according to classical Dykstra-Parsons coefficients method.The aim of this work is to investigate the effect of reservoir heterogeneity on physical process and production performance of air injection in light oil reservoir through numerical reservoir simulation approach.The basic model is calibrated based on previous study.Total eleven pseudo compounders are included in this model and ten complexity of reactions are proposed to achieve the reaction scheme.Results show that oil recovery factor is decreased with the increasing of reservoir heterogeneity both for air and N2 injection from updip location,which is against the working behavior of air injection from updip location.Reservoir heterogeneity sometimes can act as positive effect to improve sweep efficiency as well as enhance production performance for air injection.High O2 content air injection can benefit oil recovery factor,also lead to early O2 breakthrough in heterogeneous reservoir.Well-type does not show great effect on production performance for air injection in extreme heterogeneous reservoir.While adopting horizontal producer is favourable to promote production performance for air injection in homogenous reservoir.
基金supported by the National Natural Science Foundation of China (No.51974334)Hainan Province Science and Technology Special Fund (ZDYF2022SHFZ107)local efficient reform and development funds for personnel training projects supported by the central government,Heilongjiang Postdoctoral Scientific Research Fund (LBH-Q21012)。
文摘During air injection into an oil reservoir,an oxidation reaction generates some heat to raise the reservoir temperature.When the reservoir temperature reaches an ignition temperature,spontaneous ignition occurs.There is a time delay from the injection to ignition.There are mixed results regarding the feasibility of spontaneous ignition in real-field projects and in laboratory experiments.No analytical model is available in the literature to estimate the oxidation time required to reach spontaneous ignition with heat loss.This paper discusses the feasibility of spontaneous ignition from theoretical points and experimental and field project observations.An analytical model considering heat loss is proposed.Analytical models with and without heat loss investigate the factors that affect spontaneous ignition.Based on the discussion and investigations,we find that it is more difficult for spontaneous ignition to occur in laboratory experiments than in oil reservoirs;spontaneous ignition is strongly affected by the initial reservoir temperature,oil activity,and heat loss;spontaneous ignition is only possible when the initial reservoir temperature is high,the oil oxidation rate is high,and the heat loss is low.
