A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are s...A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.展开更多
A new numerical model for low-permeability reservoirs is developed.The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient.Related n...A new numerical model for low-permeability reservoirs is developed.The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient.Related numerical solutions are obtained using a finite difference method.The correctness of the method is demonstrated using a two-dimensional inhomogeneous low permeability example.Then,the differences in the cumulative oil and water production are investigated for different starting water saturations.It is shown that when the initial water saturation grows,the water content of the block continues to rise and the cumulative oil production gradually decreases.展开更多
Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evolution of d...Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evolution of dry coal under gas adsorption equilibrium,gas flow and gas diffusion within wet coal under the generally non-equilibrium state are often ignored in the process of gas recovery.In this study,an improved apparent permeability model is proposed which accommodates the water and gas adsorption,stress dependence,water film thickness and gas flow regimes.In the process of modeling,the water adsorption is only affected by water content while the gas adsorption is time and water content dependent;based on poroelastic mechanics,the effective fracture aperture and effective pore radius are derived;and then the variation in water film thickness for different pore types under the effect of water content,stress and adsorption swelling are modeled;the flow regimes are considered based on Beskok’s model.Further,after validation with experimental data,the proposed model was applied to numerical simulations to investigate the evolution of permeability-related factors under the effect of different water contents.The gas flow in wet coal under the non-equilibrium state is explicitly revealed.展开更多
The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are ...The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.展开更多
The existence of water phase occupies oil flow area and impacts the confined oil flow behavior at the solid substrate in inorganic nanopores of shale oil reservoirs,resulting in a completely different flow pattern whe...The existence of water phase occupies oil flow area and impacts the confined oil flow behavior at the solid substrate in inorganic nanopores of shale oil reservoirs,resulting in a completely different flow pattern when compared with the single oil phase flow.This study proposes an analytical model to describe the water-oil two-phase flow.In this model,water slippage at the solid substrate is considered while oil slip is introduced to calculate the oil movement at the solid-oil boundary in dry conditions.It is proven that the oil flow profiles of both the two-phase model and single-phase model show parabolic shapes,but the oil flow capacity drops when water takes up the flow space and the impact of water is more significant when the pore dimension is smaller than 30 nm.Also,the oil flow velocity at a pore center is found to drop linearly given a larger water saturation in wet conditions.The effects of surface wettability and oil properties on water-oil flow are also discussed.Compared with the existing singlephase models,this model describes oil flow pattern in the wet condition with the incorporation of the influence of nanopore properties,which better predicts the oil transport in actual reservoir conditions.Water-oil relative permeability curves are also obtained to improve oil yield.展开更多
The two-dimensional turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbo-fan jet engines are simulated by the k-ε turbulence model and the particle trajectory model. Comparison of pre...The two-dimensional turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbo-fan jet engines are simulated by the k-ε turbulence model and the particle trajectory model. Comparison of predicted gas velocity and temperature distributions with experimental results for the cases without liquid spray shows pretty good agreement. Gas-droplet two-phase flow predictions give plausible droplet trajectories, fuel-vapor concentration distribution, gas-phase velocity and temperature field in presence of liquid droplets. One run of computation with this method is made for a particular afterburner. The results indicate that the location of the atomizers is not favorable to flame stabilization and combustion efficiency. The proposed numerical modeling can also be adopted for optimization design and performance evaluation of afterburner combustors of turbo-fan jet engines.展开更多
A three-dimensional mathematical model,based on differential balances of mass and momentum,hasbeen developed to describe the two-phase flow of gas and liquid through the dropping zone of the blast fur-nace.Agreement b...A three-dimensional mathematical model,based on differential balances of mass and momentum,hasbeen developed to describe the two-phase flow of gas and liquid through the dropping zone of the blast fur-nace.Agreement between observed and calculated values verifies the validity of this model.On the basis of this model,various parameters for the surrounding of the dry zone of Blast FurnaceNo.I-BF of the Beijing Iron and Steel Company have been computed,from which a diagram for demar-cation of fluidization of coke and flooding of slag has been proposed.展开更多
Based on the displacement discontinuity method and the discrete fracture unified pipe network model,a sequential iterative numerical method was used to build a fracturing-production integrated numerical model of shale...Based on the displacement discontinuity method and the discrete fracture unified pipe network model,a sequential iterative numerical method was used to build a fracturing-production integrated numerical model of shale gas well considering the two-phase flow of gas and water.The model accounts for the influence of natural fractures and matrix properties on the fracturing process and directly applies post-fracturing formation pressure and water saturation distribution to subsequent well shut-in and production simulation,allowing for a more accurate fracturing-production integrated simulation.The results show that the reservoir physical properties have great impacts on fracture propagation,and the reasonable prediction of formation pressure and reservoir fluid distribution after the fracturing is critical to accurately predict the gas and fluid production of the shale gas wells.Compared with the conventional method,the proposed model can more accurately simulate the water and gas production by considering the impact of fracturing on both matrix pressure and water saturation.The established model is applied to the integrated fracturing-production simulation of practical horizontal shale gas wells.The simulation results are in good agreement with the practical production data,thus verifying the accuracy of the model.展开更多
A method is proposed to predict the flowing bottomhole pressures (FBHPs) for two-phase coalbed methane (CBM) wells. The mathematical models for both gas column pressure and two-phase fluid column pressure were dev...A method is proposed to predict the flowing bottomhole pressures (FBHPs) for two-phase coalbed methane (CBM) wells. The mathematical models for both gas column pressure and two-phase fluid column pressure were developed based on the well liquid flow equation. FBHPs during the production were predicted by considering the effect of entrained liquid on gravitational gradients. Comparison of calculated BHPs by Cullender-Smith and proposed method was also studied. The results show that the proposed algorithm gives the desired accuracy of calculating BHPs in the low- productivity and low-pressure CBM wells. FBHP is resulted from the combined action of wellhead pressure, gas column pressure and fluid column pressure. Variation of kinetic energy term, compressibility and friction factors with depth increments and liquid holdup with velocity should be considered to simulate the real BHPs adequately. BHP is a function of depth of each column segment. The small errors of less than 1.5% between the calculated and measured values are obtained with each segment within 25 m. Adjusting BHPs can effectively increase production pressure drop, which is beneficial to CBM desorption and enhances reservoir productivity. The increment of pressure drop from 5.37 MPa2 to 8.66 MPa2 leads to an increase of CBM production from 3270 m3/d to 6700 m3/d and is attributed to a decrease in BHP from 2.25 MPa to 1.33 MPa.展开更多
Water management in porous electrodes bears significance due to its strong potential in determining the performance of proton exchange membrane fuel cell.In terms of porous electrodes,internal water distribution and r...Water management in porous electrodes bears significance due to its strong potential in determining the performance of proton exchange membrane fuel cell.In terms of porous electrodes,internal water distribution and removal process have extensively attracted attention in both experimental and numerical studies.However,the structural difference among the catalyst layer(CL),microporous layer(MPL),and gas diffusion layer(GDL)leads to significant challenges in studying the two-phase flow behavior.Given the different porosities and pore scales of the CL,MPL,and GDL,the model scales in simulating each component are inconsistent.This review emphasizes the numerical simulation related to porous electrodes in the water transport process and evaluates the effectiveness and weakness of the conventional methods used during the investigation.The limitations of existing models include the following:(i)The reconstruction of geometric models is difficult to achieve when using the real characteristics of the components;(ii)the computational domain size is limited due to massive computational loads in three-dimensional(3 D)simulations;(iii)numerical associations among 3 D models are lacking because of the separate studies for each component;(iv)the effects of vapor condensation and heat transfer on the two-phase flow are disregarded;(v)compressive deformation during assembly and vibration in road conditions should be considered in two-phase flow studies given the real operating conditions.Therefore,this review is aimed at critical research gaps which need further investigation.Insightful potential research directions are also suggested for future improvements.展开更多
Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and ...Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and form of the transmitting roadways and the influence of obstacles.The following characterizes the propagation of coal and gas outbursts as two-phase gas-solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior.The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models.The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small comer roadways leading to significant attenuation of outburst shock waves.The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways.The most significant attenuation appears in small angle comers and bifurcations in roadways with the largest attenuation occurring in blocked roadways.These results provide basic parameters for simplifying transport in complex roadway networks in the far-field,and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.展开更多
We extend the complexity entropy causality plane(CECP) to propose a multi-scale complexity entropy causality plane(MS-CECP) and further use the proposed method to discriminate the deterministic characteristics of ...We extend the complexity entropy causality plane(CECP) to propose a multi-scale complexity entropy causality plane(MS-CECP) and further use the proposed method to discriminate the deterministic characteristics of different oil-in-water flows. We first take several typical time series for example to investigate the characteristic of the MS-CECP and find that the MS-CECP not only describes the continuous loss of dynamical structure with the increase of scale, but also reflects the determinacy of the system. Then we calculate the MS-CECP for the conductance fluctuating signals measured from oil–water two-phase flow loop test facility. The results indicate that the MS-CECP could be an intrinsic measure for indicating oil-in-water two-phase flow structures.展开更多
Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pre...Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pressure.These lead to the difficulty of water flow,which could be described by lowvelocity non-Darcy's law known as threshold pressure gradient(TPG).In this paper we firstly employ the low-velocity non-Darcy's law to describe the water flow and use Darcy flow accounting for slip flow and free molecular flow mechanisms to model gas flow in the shale formation.The sensitive study using numerical simulation shows that the proposed flow model could model the low fracturing liquid recovery and that large pseudo TPG leads to lower fracturing liquid recovery.Thus,the proposed model would give new insight to model the low water recovery in shale formations.展开更多
The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages i...The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content (10%) of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.展开更多
A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water colu...A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water column images, displaying plume characteristics, are found in gas hydrate enriched areas in the Taixinan Basin.This indicates the presence of natural gas resources in the Taixinan Basin. The multibeam sonar system is shown to provide an accurate and effective approach for detecting sub-sea gas hydrate.展开更多
Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumpin...Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.展开更多
During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas...During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.展开更多
With the increasing number of horizontal wells with low pressure,low yield,and water production,the phenomenon of water and liquid accumulation in gas wells is becoming progressively more serious.In order to fix these...With the increasing number of horizontal wells with low pressure,low yield,and water production,the phenomenon of water and liquid accumulation in gas wells is becoming progressively more serious.In order to fix these issues,it is necessary to improve existing drainage and gas recovery technologies,increase the fluid carrying capacity of these wells,and ensure that the bottom-hole airflow has enough energy to transport the liquid to the wellhead.Among the many techniques of drainage and gas recovery,the gas lift has recently become a popular method.In the present study,through the simulation of the entire horizontal well,the flow regularity of the whole wellbore during the lift of low-pressure gas has been analyzed.The pressure distribution,liquid holdup rate,flow pattern,and energy loss(including gravity loss and friction loss)have been determined using the Beggs-brill approach.It has been found that the total pressure drop of the wellbore decreases first and increases gradually after reaching a minimum value when gas extraction is carried out via gas lift.Based on the analysis of the influence of the injection volume on wellbore pressure drop and the influence of flow pattern on the lifting efficiency,the optimal gas-lift injection parameters have been determined by taking the minimum pressure loss of wellbore as the judgment criterion.展开更多
This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensio...This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.展开更多
The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties mod...The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.展开更多
基金supported by the China Postdoctoral Science Foundation(2021M702304)and Natural Science Foundation of Shandong Province(ZR2021QE260).
文摘A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.
文摘A new numerical model for low-permeability reservoirs is developed.The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient.Related numerical solutions are obtained using a finite difference method.The correctness of the method is demonstrated using a two-dimensional inhomogeneous low permeability example.Then,the differences in the cumulative oil and water production are investigated for different starting water saturations.It is shown that when the initial water saturation grows,the water content of the block continues to rise and the cumulative oil production gradually decreases.
基金the National Natural Science Foundation of China(No.52079077)the Natural Science Foundation of Shandong Province(No.ZR2021QE069).
文摘Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evolution of dry coal under gas adsorption equilibrium,gas flow and gas diffusion within wet coal under the generally non-equilibrium state are often ignored in the process of gas recovery.In this study,an improved apparent permeability model is proposed which accommodates the water and gas adsorption,stress dependence,water film thickness and gas flow regimes.In the process of modeling,the water adsorption is only affected by water content while the gas adsorption is time and water content dependent;based on poroelastic mechanics,the effective fracture aperture and effective pore radius are derived;and then the variation in water film thickness for different pore types under the effect of water content,stress and adsorption swelling are modeled;the flow regimes are considered based on Beskok’s model.Further,after validation with experimental data,the proposed model was applied to numerical simulations to investigate the evolution of permeability-related factors under the effect of different water contents.The gas flow in wet coal under the non-equilibrium state is explicitly revealed.
基金supported by the National Natural Science Foundation of China (42074142, 51527805, 41974139)China Postdoctoral Science Foundation (2020M680969, 2021T140099)the Fundamental Research Funds for the Central Universities (N2104013)。
文摘The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.
基金the NSERC/Energi Simulation and Alberta Innovates Chairs for providing research fundingthe Beijing Natural Science Foundation(2204093)Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC033)for providing research funding。
文摘The existence of water phase occupies oil flow area and impacts the confined oil flow behavior at the solid substrate in inorganic nanopores of shale oil reservoirs,resulting in a completely different flow pattern when compared with the single oil phase flow.This study proposes an analytical model to describe the water-oil two-phase flow.In this model,water slippage at the solid substrate is considered while oil slip is introduced to calculate the oil movement at the solid-oil boundary in dry conditions.It is proven that the oil flow profiles of both the two-phase model and single-phase model show parabolic shapes,but the oil flow capacity drops when water takes up the flow space and the impact of water is more significant when the pore dimension is smaller than 30 nm.Also,the oil flow velocity at a pore center is found to drop linearly given a larger water saturation in wet conditions.The effects of surface wettability and oil properties on water-oil flow are also discussed.Compared with the existing singlephase models,this model describes oil flow pattern in the wet condition with the incorporation of the influence of nanopore properties,which better predicts the oil transport in actual reservoir conditions.Water-oil relative permeability curves are also obtained to improve oil yield.
文摘The two-dimensional turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbo-fan jet engines are simulated by the k-ε turbulence model and the particle trajectory model. Comparison of predicted gas velocity and temperature distributions with experimental results for the cases without liquid spray shows pretty good agreement. Gas-droplet two-phase flow predictions give plausible droplet trajectories, fuel-vapor concentration distribution, gas-phase velocity and temperature field in presence of liquid droplets. One run of computation with this method is made for a particular afterburner. The results indicate that the location of the atomizers is not favorable to flame stabilization and combustion efficiency. The proposed numerical modeling can also be adopted for optimization design and performance evaluation of afterburner combustors of turbo-fan jet engines.
文摘A three-dimensional mathematical model,based on differential balances of mass and momentum,hasbeen developed to describe the two-phase flow of gas and liquid through the dropping zone of the blast fur-nace.Agreement between observed and calculated values verifies the validity of this model.On the basis of this model,various parameters for the surrounding of the dry zone of Blast FurnaceNo.I-BF of the Beijing Iron and Steel Company have been computed,from which a diagram for demar-cation of fluidization of coke and flooding of slag has been proposed.
基金Supported by the National Natural Science Foundation of China(52374043)Key Program of the National Natural Science Foundation of China(52234003).
文摘Based on the displacement discontinuity method and the discrete fracture unified pipe network model,a sequential iterative numerical method was used to build a fracturing-production integrated numerical model of shale gas well considering the two-phase flow of gas and water.The model accounts for the influence of natural fractures and matrix properties on the fracturing process and directly applies post-fracturing formation pressure and water saturation distribution to subsequent well shut-in and production simulation,allowing for a more accurate fracturing-production integrated simulation.The results show that the reservoir physical properties have great impacts on fracture propagation,and the reasonable prediction of formation pressure and reservoir fluid distribution after the fracturing is critical to accurately predict the gas and fluid production of the shale gas wells.Compared with the conventional method,the proposed model can more accurately simulate the water and gas production by considering the impact of fracturing on both matrix pressure and water saturation.The established model is applied to the integrated fracturing-production simulation of practical horizontal shale gas wells.The simulation results are in good agreement with the practical production data,thus verifying the accuracy of the model.
基金part of a key project carried out in 2009–2010financially supported by the National Key Sci-Tech Major Special Item (Grant No. 2009ZX05038)
文摘A method is proposed to predict the flowing bottomhole pressures (FBHPs) for two-phase coalbed methane (CBM) wells. The mathematical models for both gas column pressure and two-phase fluid column pressure were developed based on the well liquid flow equation. FBHPs during the production were predicted by considering the effect of entrained liquid on gravitational gradients. Comparison of calculated BHPs by Cullender-Smith and proposed method was also studied. The results show that the proposed algorithm gives the desired accuracy of calculating BHPs in the low- productivity and low-pressure CBM wells. FBHP is resulted from the combined action of wellhead pressure, gas column pressure and fluid column pressure. Variation of kinetic energy term, compressibility and friction factors with depth increments and liquid holdup with velocity should be considered to simulate the real BHPs adequately. BHP is a function of depth of each column segment. The small errors of less than 1.5% between the calculated and measured values are obtained with each segment within 25 m. Adjusting BHPs can effectively increase production pressure drop, which is beneficial to CBM desorption and enhances reservoir productivity. The increment of pressure drop from 5.37 MPa2 to 8.66 MPa2 leads to an increase of CBM production from 3270 m3/d to 6700 m3/d and is attributed to a decrease in BHP from 2.25 MPa to 1.33 MPa.
基金supported by the National Natural Science Foundation of China(No.51676135)the National Key Research and Development Program of China(No.2018YFB0105505)。
文摘Water management in porous electrodes bears significance due to its strong potential in determining the performance of proton exchange membrane fuel cell.In terms of porous electrodes,internal water distribution and removal process have extensively attracted attention in both experimental and numerical studies.However,the structural difference among the catalyst layer(CL),microporous layer(MPL),and gas diffusion layer(GDL)leads to significant challenges in studying the two-phase flow behavior.Given the different porosities and pore scales of the CL,MPL,and GDL,the model scales in simulating each component are inconsistent.This review emphasizes the numerical simulation related to porous electrodes in the water transport process and evaluates the effectiveness and weakness of the conventional methods used during the investigation.The limitations of existing models include the following:(i)The reconstruction of geometric models is difficult to achieve when using the real characteristics of the components;(ii)the computational domain size is limited due to massive computational loads in three-dimensional(3 D)simulations;(iii)numerical associations among 3 D models are lacking because of the separate studies for each component;(iv)the effects of vapor condensation and heat transfer on the two-phase flow are disregarded;(v)compressive deformation during assembly and vibration in road conditions should be considered in two-phase flow studies given the real operating conditions.Therefore,this review is aimed at critical research gaps which need further investigation.Insightful potential research directions are also suggested for future improvements.
基金the State Key Research Development Program of China(Grant No.2018YFC0808101)the National Natural Science Foundation of China(51774292,51874314,51604278,51804312)the Yue Qi Distinguished Scholar Project,China University of Mining&Technology,Beijing,the Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing.
文摘Coal and gas outbursts compromise two-phase gas-solid mixtures as they propagate as shock waves and flows from their sources.Propagation is influenced by the form of the outburst,proximity to source,the structure and form of the transmitting roadways and the influence of obstacles.The following characterizes the propagation of coal and gas outbursts as two-phase gas-solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior.The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models.The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small comer roadways leading to significant attenuation of outburst shock waves.The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways.The most significant attenuation appears in small angle comers and bifurcations in roadways with the largest attenuation occurring in blocked roadways.These results provide basic parameters for simplifying transport in complex roadway networks in the far-field,and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41174109 and 61104148)the National Science and Technology Major Project of China(Grant No.2011ZX05020-006)the Zhejiang Key Discipline of Instrument Science and Technology,China(Grant No.JL130106)
文摘We extend the complexity entropy causality plane(CECP) to propose a multi-scale complexity entropy causality plane(MS-CECP) and further use the proposed method to discriminate the deterministic characteristics of different oil-in-water flows. We first take several typical time series for example to investigate the characteristic of the MS-CECP and find that the MS-CECP not only describes the continuous loss of dynamical structure with the increase of scale, but also reflects the determinacy of the system. Then we calculate the MS-CECP for the conductance fluctuating signals measured from oil–water two-phase flow loop test facility. The results indicate that the MS-CECP could be an intrinsic measure for indicating oil-in-water two-phase flow structures.
基金supported by the National Natural Science Foundation of China(Grant No.1217020361).
文摘Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pressure.These lead to the difficulty of water flow,which could be described by lowvelocity non-Darcy's law known as threshold pressure gradient(TPG).In this paper we firstly employ the low-velocity non-Darcy's law to describe the water flow and use Darcy flow accounting for slip flow and free molecular flow mechanisms to model gas flow in the shale formation.The sensitive study using numerical simulation shows that the proposed flow model could model the low fracturing liquid recovery and that large pseudo TPG leads to lower fracturing liquid recovery.Thus,the proposed model would give new insight to model the low water recovery in shale formations.
基金support from Subtopics of National Science and Technology Major Project(2011ZX05026-004-03)the National Natural Science Foundation of China (51104167)
文摘The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content (10%) of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.
基金The National Key R&D Program of China under contract No.2017YFC0306003the National Natural Science Foundation of China under contract Nos 41506069,41876111 and 40706038
文摘A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water column images, displaying plume characteristics, are found in gas hydrate enriched areas in the Taixinan Basin.This indicates the presence of natural gas resources in the Taixinan Basin. The multibeam sonar system is shown to provide an accurate and effective approach for detecting sub-sea gas hydrate.
基金supported by the National Natural Science Foundation of China(52176040)Shandong Provincial Natural Science Foundation of China(ZR2018LE015)。
文摘Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.
基金supported by the Youth Program of National Natural Science Foundation of China(Grant No.52104012)the Key Program of the National Natural Science Foundation of China(Grant No.51734010)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M693494)Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKBH011)the Key Natural Science Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region(Grant No.XJEDU2021I028)。
文摘During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.
基金supported by National Natural Science Foundation of China(No.61572084)the National Key Research and Development Program of China(2016ZX05056004-002,2017ZX05030-005).
文摘With the increasing number of horizontal wells with low pressure,low yield,and water production,the phenomenon of water and liquid accumulation in gas wells is becoming progressively more serious.In order to fix these issues,it is necessary to improve existing drainage and gas recovery technologies,increase the fluid carrying capacity of these wells,and ensure that the bottom-hole airflow has enough energy to transport the liquid to the wellhead.Among the many techniques of drainage and gas recovery,the gas lift has recently become a popular method.In the present study,through the simulation of the entire horizontal well,the flow regularity of the whole wellbore during the lift of low-pressure gas has been analyzed.The pressure distribution,liquid holdup rate,flow pattern,and energy loss(including gravity loss and friction loss)have been determined using the Beggs-brill approach.It has been found that the total pressure drop of the wellbore decreases first and increases gradually after reaching a minimum value when gas extraction is carried out via gas lift.Based on the analysis of the influence of the injection volume on wellbore pressure drop and the influence of flow pattern on the lifting efficiency,the optimal gas-lift injection parameters have been determined by taking the minimum pressure loss of wellbore as the judgment criterion.
文摘This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.
基金supported under the strategic academic leadership program“Priority 2030”of the Russian Federation(Agreement 075-15-2021-1333 dated 30.09.2021).
文摘The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.