The high temperature and high pressure visualization pressure-volume-temperature(PVT)experiments of different gas media-crude oil were carried using the interface disappearance method.There are two miscible temperatur...The high temperature and high pressure visualization pressure-volume-temperature(PVT)experiments of different gas media-crude oil were carried using the interface disappearance method.There are two miscible temperature domains in the miscibility of CO_(2)-crude oil during heating process under constant pressure.Under the experiment pressure of 15 MPa,when the temperature is less than 140℃,the miscible zone shows liquid phase characteristics,and increasing the temperature inhibits the miscible process;when the temperature is greater than 230℃,the miscible zone tends to show gas phase characteristics,and increasing the temperature is conducive to the miscibility formation.Under a certain pressure,with the increase of temperature,the miscibility of flue gas,nitrogen and crude oil is realized.When the temperature is low,the effect of CO_(2) on promoting miscibility is obvious,and the order of miscible temperature of gas medium and crude oil is N_(2)>flue gas>CO_(2);however,when the temperature is high,the effect of CO_(2) on promoting miscibility gradually decreases,and the miscible temperature of N_(2) and crude oil is close to that of flue gas.The miscibility is dominated by the distillation and volatilization of light components of crude oil.There are many light hydrocarbon components in the gas phase at phase equilibrium,and the miscible zone is characterized by gas phase.展开更多
CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has ...CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has constrained the broader industrial application of CO_(2)geo-sequestration.This work develops a pore-scale numerical model considering molecular convection–diffusion to investigate CO_(2)-oil miscible displacement in two-and three-dimensional porous structures of conglomerate rocks.The effects of CO_(2)injection rates and pore structure properties on convection–diffusion are analyzed.By reconstructing the distribution of unexploited pores,the CO_(2)sweep efficiency is quantitatively evaluated.Furthermore,a sequestration factor is proposed to evaluate the CO_(2)storage capacity during miscible displacement.Convection significantly enhances the CO_(2)mass fraction in fractures with high flow rates.Subsequently,CO_(2)gradually diffuses into matrix pores without velocity distribution.Both convection and diffusion contribute to improving CO_(2)displacement efficiency.Diffusion facilitates the dissolution of CO_(2)into oil within small-diameter pores,and convection effectively mobilizes oil in large pore bodies.Developed and homogeneous pore structures enhance CO_(2)displacement efficiency,whereas CO_(2)flows along the main flow channels in heterogeneous pore structures,resulting in lower displacement efficiency.Diffusion plays a crucial role in CO_(2)storage within porous media.At low injection rates,dissolved CO_(2)is trapped in poorly connected and blind-end pores.The injection rate is negatively correlated with the sequestration factor.展开更多
A modification of a finite element method of Douglas and Roberts for approximating the solution of the equations describing compressible miscible displacement in a porous medium is proposed and analyzed. The pressure ...A modification of a finite element method of Douglas and Roberts for approximating the solution of the equations describing compressible miscible displacement in a porous medium is proposed and analyzed. The pressure is treated by a parabolic mixed finite element method using a Raviart-Thomas space of index rover a quasiregular partition, An extension of the Darcy velocity along Gauss lines is used in the evaluation of the coefficients in the Galerkin procedure for the concentration. A simple computational procedure allows the superconvergence property of the fluid velocity to be retained in our total algorithm.展开更多
Physical modeling,numerical simulation and field case analysis were carried out to find out the subsurface thermal oxidation state,thermal oxidation front characteristics and production dynamic characteristics of high...Physical modeling,numerical simulation and field case analysis were carried out to find out the subsurface thermal oxidation state,thermal oxidation front characteristics and production dynamic characteristics of high pressure air injection thermal oxidation miscible flooding technology.The lighter the composition and the lower the viscosity of the crude oil,the lower the fuel consumption and the combustion temperature are.The thermal oxidation front of light oil and volatile oil can advance stably,and a medium-temperature thermal oxidation stable displacement state can be formed in the light oil reservoir under high pressure conditions.With strong thermal gasification and distillation,light oil and volatile oil are likely to form a single phase zone of gasification and distillation with thermal flue gas at the high-temperature and high-pressure heat front,finally,an air-injection thermal miscible front.In light oil reservoirs,the development process of high-pressure air-injection thermal miscible flooding can be divided into three stages:boosting pressure stage,low gas-oil ratio and high-efficiency stable production stage and high gas-oil ratio production stage.Approximately 70%of crude oil is produced during the boosting pressure stage and low gas-oil ratio high-efficiency and stable production stage.展开更多
An efficient time stepping procedure is proposed to treat the system describing compressible miscible displacement in a porous medium by employing a mixed finite element method to approximate the pressure and the flui...An efficient time stepping procedure is proposed to treat the system describing compressible miscible displacement in a porous medium by employing a mixed finite element method to approximate the pressure and the fluid velocity and a standard Galerkin method to approximate the concentration. An extension of the Darcy velocity along Gauss lines is used in the evaluation of the coefficients in the Galerkin procedure for the concentration. These results show that the total algorithm has the superconvergence property of the fluid velocity.展开更多
The miscible displacement of one incompressible fluid by another in a porous medium is considered in this paper. The concentration is split in a first-order hyberbolic equation and a homogeneous parabolic equation wit...The miscible displacement of one incompressible fluid by another in a porous medium is considered in this paper. The concentration is split in a first-order hyberbolic equation and a homogeneous parabolic equation within each lime step. The pressure and Us velocity field is computed by a mixed finite element method. Optimal order estimates are derived for the no diffusion case and the diffusion case.展开更多
The purpose of this study is to optimize the existing carbon dioxide （CO2） flood in deep dolomite formations by improving oil sweep efficiency of miscible CO2 floods and enhancing the conformance control. A full com...The purpose of this study is to optimize the existing carbon dioxide （CO2） flood in deep dolomite formations by improving oil sweep efficiency of miscible CO2 floods and enhancing the conformance control. A full compositional simulation model using a detailed geologic characterization was built to optimize the injection pattern. The model is a quarter of an inverted nine-spot and covers 20 acres of field formation. Geologic description was used to construct the simulation grids. The simulation layers represent actual flow units and resemble the large variation of reservoir properties. History match was performed to validate the model. Several sensitivity runs were made to improve the CO2 sweep efficiency and increase the oil recovery. Finally, the optimum CO2 injection rate for dolomite formations was determined approximately. Simulation results also indicate that a water-alternating-gas （WAG） ratio of 1：1 along with an ultimate CO2 slug of 100% hydrocarbon pore volume （HCPV） will allow an incremental oil recovery of 18%. The additional recovery increases to 34% if a polymer is injected as a conformance control agent during the course of the WAG process at a ratio of 1：1. According to the results, a pattern reconfiguration change from the nine spot to staggered line drive would represent an incremental oil recovery of 26%.展开更多
We consider a nonlinear parabolic system describing compressible miscibledisplacement in a porous medium [5]. Continuous time and discrete time Galerkinmethods are introduced to approximate the solution and optimal H^...We consider a nonlinear parabolic system describing compressible miscibledisplacement in a porous medium [5]. Continuous time and discrete time Galerkinmethods are introduced to approximate the solution and optimal H^1 error estimatesare obtained. One contribution of this paper is a demonstration of how moleculardispersion can be handled.展开更多
The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,a...The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.展开更多
The characteristics and the formation of the miscible particles in V-Ti-N microalloyed steels were studied.It was found that the vanadium to form V-Ti miscible particles starts to precipi- tate after pouring and cooli...The characteristics and the formation of the miscible particles in V-Ti-N microalloyed steels were studied.It was found that the vanadium to form V-Ti miscible particles starts to precipi- tate after pouring and cooling to temperature below 11 50℃ by means of the epitaxial precipi- tation on the pre-existing titanium nitrides.The vanadium content in the particles is markedly influenced by the cooling rate after solidification.展开更多
In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and t...In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and the approximation accuracy of Darch-Forchheimer velocity is improved one order.The concentration equation is solved by the method of mixed finite element,where the convection is discretized along the characteristic direction and the diffusion is discretized by the zero-order mixed finite element method.The characteristics can confirm strong stability at sharp fronts and avoids numerical dispersion and nonphysical oscillation.In actual computations the characteristics adopts a large time step without any loss of accuracy.The scalar unknowns and its adjoint vector function are obtained simultaneously and the law of mass conservation holds in every element by the zero-order mixed finite element discretization of diffusion flux.In order to derive the optimal 3/2-order error estimate in L^(2) norm,a post-processing technique is included in the approximation to the scalar unknowns.Numerical experiments are illustrated finally to validate theoretical analysis and efficiency.This method can be used to solve such an important problem.展开更多
The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and...The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and atomic force microscopy （AFM）, respectively. This blend exhibited a lower critical solution temperature behavior. Below 120 ℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.展开更多
There are various issues for CO_(2)flooding and storage in Shengli Oilfield,which are characterized by low light hydrocarbon content of oil and high miscible pressure,strong reservoir heterogeneity and low sweep effic...There are various issues for CO_(2)flooding and storage in Shengli Oilfield,which are characterized by low light hydrocarbon content of oil and high miscible pressure,strong reservoir heterogeneity and low sweep efficiency,gas channeling and difficult whole-process control.Through laboratory experiments,technical research and field practice,the theory and technology of CO_(2)high pressure miscible flooding and storage are established.By increasing the formation pressure to 1.2 times the minimum miscible pressure,the miscibility of the medium-heavy components can be improved,the production percentage of oil in small pores can be increased,the displacing front developed evenly,and the swept volume expanded.Rapid high-pressure miscibility is realized through advanced pressure flooding and energy replenishment,and technologies of cascade water-alternating-gas(WAG),injection and production coupling and multistage chemical plugging are used for dynamic control of flow resistance,so as to obtain the optimum of oil recovery and CO_(2)storage factor.The research results have been applied to the Gao89-Fan142 in carbon capture,utilization and storage(CCUS)demonstration site,where the daily oil production of the block has increased from 254.6 t to 358.2 t,and the recovery degree is expected to increase by 11.6 percentage points in 15 years,providing theoretical and technical support for the large-scale development of CCUS.展开更多
Recent experiments have shown that hole traps could be suppressed in polymer light-emitting diodes under current stress by diluting the light-emitting conjugated polymers within an“inert”large-bandgap host material....Recent experiments have shown that hole traps could be suppressed in polymer light-emitting diodes under current stress by diluting the light-emitting conjugated polymers within an“inert”large-bandgap host material.However,it is unclear why there is an enhanced dilution effect in partially miscible blends rather than fully miscible blends,as intuition would suggest that better miscibility leads to better dilution.In this work,we propose a cascade analysis by combining multiple fluorescence microscopic techniques and all-atom molecular dynamics simulations to study the solid-to-solid dilution of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV)inMEH-PPV/polystyrene(PS)blends and MEH-PPV/poly(vinylcarbazole)(PVK)blends.By varying the molecular weights of PS and PVK,we can regulate their miscibility with MEH-PPV.The results corroborate that the dilution effect is enhanced in partially miscible blends rather than fully miscible ones.This is because,in partially miscible blends undergoing phase separation,the concentration of MEH-PPV is notably decreased in the phase occupying the majority of the volume,leading to an overall greater dilution effect than in fully miscible blends.Moreover,MEH-PPV could adopt the more extended conformation in the fully miscible blend,causing a shorter intermolecular distance to further undermine the dilution effect.These findings explain the seemingly counterintuitive more effective dilution effect observed in the recently reported partially miscible blends and provide guidance for further enhancing the performance of future generations of polymer light-emitting diodes.展开更多
Numerical simulation of two-phase (oil and water) miscible flow in porousmedia is the mathematical foundation in energy problems. For a two-dimensional posi-tive problem, Douglas put forward the well-known characteris...Numerical simulation of two-phase (oil and water) miscible flow in porousmedia is the mathematical foundation in energy problems. For a two-dimensional posi-tive problem, Douglas put forward the well-known characteristic finite difference method.However, for numerical analysis there exist difficulties. They assumed that the problem isperiodic and the diffusion matrix of the concentration equation was positive definite. Butin many practical situations the diffusion matrixes are only positive semidefinite. In thispaper, we put forward a kind of characteristic finite difference schemes and obtain optimalorder estimates in l2 norm for the error in the approximation assumptions.展开更多
A kind of compressible miscible displacement problems which include molecular diffusion and dispersion in porous media are investigated.A symmetric interior penalty discontinuous Galerkin (SIPG) method is applied to t...A kind of compressible miscible displacement problems which include molecular diffusion and dispersion in porous media are investigated.A symmetric interior penalty discontinuous Galerkin (SIPG) method is applied to the coupled system of flow and transport.Using the induction hypotheses instead of the cut-off operator and the interpolation projection properties,a priori hp error estimates are presented.The error bounds in L2(H1) norm for concentration and in L∞(L2) norm for velocity are optimal in h and suboptimal in p with a loss of power 1/2.展开更多
Under the assumptions of nonlinear finite element and △t=o(h),Ewing and Wheeler discussed a Galerkin method for the single phase incompressible miscible displacement of one fluid by another in porous media.In the pre...Under the assumptions of nonlinear finite element and △t=o(h),Ewing and Wheeler discussed a Galerkin method for the single phase incompressible miscible displacement of one fluid by another in porous media.In the present paper we give a finite element scheme which weakens the △t=o(h)-restriction to △t=o(h~ε),0<ε≤1/2.Furthermore,this scheme is suitable for both linear element and nonlinear element.We also derive the optimal approximation estimates for concentration c,its gradient ▽c and the gradient ▽p of the pressure p.展开更多
A nonlinear parabolic system is derived to describe compressible miscible displacement in a porous medium.The concentration equation is treated by a mixed finite element method with characteristics(CMFEM)and the press...A nonlinear parabolic system is derived to describe compressible miscible displacement in a porous medium.The concentration equation is treated by a mixed finite element method with characteristics(CMFEM)and the pressure equation is treated by a parabolic mixed finite element method(PMFEM).Two-grid algorithm is considered to linearize nonlinear coupled system of two parabolic partial differential equations.Moreover,the L q error estimates are conducted for the pressure,Darcy velocity and concentration variables in the two-grid solutions.Both theoretical analysis and numerical experiments are presented to show that the two-grid algorithm is very effective.展开更多
A combined method consisting of the mixed finite element method for flow and the local discontinuous Galerkin method for transport is introduced for the one-dimensional coupled system of incompressible miscible displa...A combined method consisting of the mixed finite element method for flow and the local discontinuous Galerkin method for transport is introduced for the one-dimensional coupled system of incompressible miscible displacement problem. Optimal error estimates in L∞(0,T;L2) for concentration c,in L2(0,T;L2)for cxand L∞(0,T;L2) for velocity u are derived. The main technical difficulties in the analysis include the treatment of the inter-element jump terms which arise from the discontinuous nature of the numerical method,the nonlinearity,and the coupling of the models. Numerical experiments are performed to verify the theoretical results. Finally,we apply this method to the one-dimensional compressible miscible displacement problem and give the numerical experiments to confirm the efficiency of the scheme.展开更多
The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this pa...The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this paper,we present a mixed finite volume element method(FVEM)for the approximation of the pressure–velocity equation and a standard FVEM for the concentration equation.A priori error estimates in L^(∞)(L^(2))are derived for velocity,pressure and concentration.Numerical results are presented to substantiate the validity of the theoretical results.展开更多
基金Supported by the Petro China Science and Technology Project(2023ZG18)。
文摘The high temperature and high pressure visualization pressure-volume-temperature(PVT)experiments of different gas media-crude oil were carried using the interface disappearance method.There are two miscible temperature domains in the miscibility of CO_(2)-crude oil during heating process under constant pressure.Under the experiment pressure of 15 MPa,when the temperature is less than 140℃,the miscible zone shows liquid phase characteristics,and increasing the temperature inhibits the miscible process;when the temperature is greater than 230℃,the miscible zone tends to show gas phase characteristics,and increasing the temperature is conducive to the miscibility formation.Under a certain pressure,with the increase of temperature,the miscibility of flue gas,nitrogen and crude oil is realized.When the temperature is low,the effect of CO_(2) on promoting miscibility is obvious,and the order of miscible temperature of gas medium and crude oil is N_(2)>flue gas>CO_(2);however,when the temperature is high,the effect of CO_(2) on promoting miscibility gradually decreases,and the miscible temperature of N_(2) and crude oil is close to that of flue gas.The miscibility is dominated by the distillation and volatilization of light components of crude oil.There are many light hydrocarbon components in the gas phase at phase equilibrium,and the miscible zone is characterized by gas phase.
基金supported by National Natural Science Foundation of China(42172159,52404048)China Postdoctoral Science Foundation(2023M743870)+1 种基金Postdoctoral Fellowship Program of CPSF(GZB20230864)Frontier Interdisciplinary Exploration Research Program of China University of Petroleum,Beijing(2462024XKQY002).
文摘CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has constrained the broader industrial application of CO_(2)geo-sequestration.This work develops a pore-scale numerical model considering molecular convection–diffusion to investigate CO_(2)-oil miscible displacement in two-and three-dimensional porous structures of conglomerate rocks.The effects of CO_(2)injection rates and pore structure properties on convection–diffusion are analyzed.By reconstructing the distribution of unexploited pores,the CO_(2)sweep efficiency is quantitatively evaluated.Furthermore,a sequestration factor is proposed to evaluate the CO_(2)storage capacity during miscible displacement.Convection significantly enhances the CO_(2)mass fraction in fractures with high flow rates.Subsequently,CO_(2)gradually diffuses into matrix pores without velocity distribution.Both convection and diffusion contribute to improving CO_(2)displacement efficiency.Diffusion facilitates the dissolution of CO_(2)into oil within small-diameter pores,and convection effectively mobilizes oil in large pore bodies.Developed and homogeneous pore structures enhance CO_(2)displacement efficiency,whereas CO_(2)flows along the main flow channels in heterogeneous pore structures,resulting in lower displacement efficiency.Diffusion plays a crucial role in CO_(2)storage within porous media.At low injection rates,dissolved CO_(2)is trapped in poorly connected and blind-end pores.The injection rate is negatively correlated with the sequestration factor.
基金Supported by China State Major Rey Project for Basic Researches
文摘A modification of a finite element method of Douglas and Roberts for approximating the solution of the equations describing compressible miscible displacement in a porous medium is proposed and analyzed. The pressure is treated by a parabolic mixed finite element method using a Raviart-Thomas space of index rover a quasiregular partition, An extension of the Darcy velocity along Gauss lines is used in the evaluation of the coefficients in the Galerkin procedure for the concentration. A simple computational procedure allows the superconvergence property of the fluid velocity to be retained in our total algorithm.
基金Supported by the Science and Technology Project of PetroChina Exploration and Production Company.
文摘Physical modeling,numerical simulation and field case analysis were carried out to find out the subsurface thermal oxidation state,thermal oxidation front characteristics and production dynamic characteristics of high pressure air injection thermal oxidation miscible flooding technology.The lighter the composition and the lower the viscosity of the crude oil,the lower the fuel consumption and the combustion temperature are.The thermal oxidation front of light oil and volatile oil can advance stably,and a medium-temperature thermal oxidation stable displacement state can be formed in the light oil reservoir under high pressure conditions.With strong thermal gasification and distillation,light oil and volatile oil are likely to form a single phase zone of gasification and distillation with thermal flue gas at the high-temperature and high-pressure heat front,finally,an air-injection thermal miscible front.In light oil reservoirs,the development process of high-pressure air-injection thermal miscible flooding can be divided into three stages:boosting pressure stage,low gas-oil ratio and high-efficiency stable production stage and high gas-oil ratio production stage.Approximately 70%of crude oil is produced during the boosting pressure stage and low gas-oil ratio high-efficiency and stable production stage.
文摘An efficient time stepping procedure is proposed to treat the system describing compressible miscible displacement in a porous medium by employing a mixed finite element method to approximate the pressure and the fluid velocity and a standard Galerkin method to approximate the concentration. An extension of the Darcy velocity along Gauss lines is used in the evaluation of the coefficients in the Galerkin procedure for the concentration. These results show that the total algorithm has the superconvergence property of the fluid velocity.
基金This work was supported by China State Major Key Project for Basic Researches.
文摘The miscible displacement of one incompressible fluid by another in a porous medium is considered in this paper. The concentration is split in a first-order hyberbolic equation and a homogeneous parabolic equation within each lime step. The pressure and Us velocity field is computed by a mixed finite element method. Optimal order estimates are derived for the no diffusion case and the diffusion case.
文摘The purpose of this study is to optimize the existing carbon dioxide （CO2） flood in deep dolomite formations by improving oil sweep efficiency of miscible CO2 floods and enhancing the conformance control. A full compositional simulation model using a detailed geologic characterization was built to optimize the injection pattern. The model is a quarter of an inverted nine-spot and covers 20 acres of field formation. Geologic description was used to construct the simulation grids. The simulation layers represent actual flow units and resemble the large variation of reservoir properties. History match was performed to validate the model. Several sensitivity runs were made to improve the CO2 sweep efficiency and increase the oil recovery. Finally, the optimum CO2 injection rate for dolomite formations was determined approximately. Simulation results also indicate that a water-alternating-gas （WAG） ratio of 1：1 along with an ultimate CO2 slug of 100% hydrocarbon pore volume （HCPV） will allow an incremental oil recovery of 18%. The additional recovery increases to 34% if a polymer is injected as a conformance control agent during the course of the WAG process at a ratio of 1：1. According to the results, a pattern reconfiguration change from the nine spot to staggered line drive would represent an incremental oil recovery of 26%.
基金The work is supported by Science Foundation of the Educational Committee of Shandong Province.
文摘We consider a nonlinear parabolic system describing compressible miscibledisplacement in a porous medium [5]. Continuous time and discrete time Galerkinmethods are introduced to approximate the solution and optimal H^1 error estimatesare obtained. One contribution of this paper is a demonstration of how moleculardispersion can be handled.
基金The financial supports from the National Natural Science Foundation of China(22178014)。
文摘The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.
文摘The characteristics and the formation of the miscible particles in V-Ti-N microalloyed steels were studied.It was found that the vanadium to form V-Ti miscible particles starts to precipi- tate after pouring and cooling to temperature below 11 50℃ by means of the epitaxial precipi- tation on the pre-existing titanium nitrides.The vanadium content in the particles is markedly influenced by the cooling rate after solidification.
基金supported by the Natural ScienceFoundation of Shandong Province(ZR2021MA019)。
文摘In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and the approximation accuracy of Darch-Forchheimer velocity is improved one order.The concentration equation is solved by the method of mixed finite element,where the convection is discretized along the characteristic direction and the diffusion is discretized by the zero-order mixed finite element method.The characteristics can confirm strong stability at sharp fronts and avoids numerical dispersion and nonphysical oscillation.In actual computations the characteristics adopts a large time step without any loss of accuracy.The scalar unknowns and its adjoint vector function are obtained simultaneously and the law of mass conservation holds in every element by the zero-order mixed finite element discretization of diffusion flux.In order to derive the optimal 3/2-order error estimate in L^(2) norm,a post-processing technique is included in the approximation to the scalar unknowns.Numerical experiments are illustrated finally to validate theoretical analysis and efficiency.This method can be used to solve such an important problem.
基金supported by the Major International (Regional) Joint Research Project of the National Natural Science Foundation of China (No. 51210004)the National Natural Science Foundation of China (No. 50903035)Chinese Ministry of Education (NCET-11-0174)
文摘The miscibility of poly（vinyl chloride）/poly（n-butyl methacrylate） （PVC/PnBMA） blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry （DSC） and atomic force microscopy （AFM）, respectively. This blend exhibited a lower critical solution temperature behavior. Below 120 ℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.
基金Supported by the Sinopec"Ten Dragon"Major ProjectKey Research Projects of Sinopec(P22180)。
文摘There are various issues for CO_(2)flooding and storage in Shengli Oilfield,which are characterized by low light hydrocarbon content of oil and high miscible pressure,strong reservoir heterogeneity and low sweep efficiency,gas channeling and difficult whole-process control.Through laboratory experiments,technical research and field practice,the theory and technology of CO_(2)high pressure miscible flooding and storage are established.By increasing the formation pressure to 1.2 times the minimum miscible pressure,the miscibility of the medium-heavy components can be improved,the production percentage of oil in small pores can be increased,the displacing front developed evenly,and the swept volume expanded.Rapid high-pressure miscibility is realized through advanced pressure flooding and energy replenishment,and technologies of cascade water-alternating-gas(WAG),injection and production coupling and multistage chemical plugging are used for dynamic control of flow resistance,so as to obtain the optimum of oil recovery and CO_(2)storage factor.The research results have been applied to the Gao89-Fan142 in carbon capture,utilization and storage(CCUS)demonstration site,where the daily oil production of the block has increased from 254.6 t to 358.2 t,and the recovery degree is expected to increase by 11.6 percentage points in 15 years,providing theoretical and technical support for the large-scale development of CCUS.
基金support from the National Natural Science Foundation of China(no.22073091)the National Key Research and Development Program of China(no.2021YFC2101700)+2 种基金the Youth Growth Science and Technology Program of Jilin Province(no.20220508023RC)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(no.ZDBS-LY-SLH033)the Technological Innovation Project of Instrument and Equipment Function Development,Chinese Academy of Sciences.
文摘Recent experiments have shown that hole traps could be suppressed in polymer light-emitting diodes under current stress by diluting the light-emitting conjugated polymers within an“inert”large-bandgap host material.However,it is unclear why there is an enhanced dilution effect in partially miscible blends rather than fully miscible blends,as intuition would suggest that better miscibility leads to better dilution.In this work,we propose a cascade analysis by combining multiple fluorescence microscopic techniques and all-atom molecular dynamics simulations to study the solid-to-solid dilution of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV)inMEH-PPV/polystyrene(PS)blends and MEH-PPV/poly(vinylcarbazole)(PVK)blends.By varying the molecular weights of PS and PVK,we can regulate their miscibility with MEH-PPV.The results corroborate that the dilution effect is enhanced in partially miscible blends rather than fully miscible ones.This is because,in partially miscible blends undergoing phase separation,the concentration of MEH-PPV is notably decreased in the phase occupying the majority of the volume,leading to an overall greater dilution effect than in fully miscible blends.Moreover,MEH-PPV could adopt the more extended conformation in the fully miscible blend,causing a shorter intermolecular distance to further undermine the dilution effect.These findings explain the seemingly counterintuitive more effective dilution effect observed in the recently reported partially miscible blends and provide guidance for further enhancing the performance of future generations of polymer light-emitting diodes.
文摘Numerical simulation of two-phase (oil and water) miscible flow in porousmedia is the mathematical foundation in energy problems. For a two-dimensional posi-tive problem, Douglas put forward the well-known characteristic finite difference method.However, for numerical analysis there exist difficulties. They assumed that the problem isperiodic and the diffusion matrix of the concentration equation was positive definite. Butin many practical situations the diffusion matrixes are only positive semidefinite. In thispaper, we put forward a kind of characteristic finite difference schemes and obtain optimalorder estimates in l2 norm for the error in the approximation assumptions.
基金supported by National Natural Science Foundation of China (Grant No.10971074)the Foundation for Talent Introduction of Guangdong Provincial University,Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2008)+2 种基金the National Basic Research Program (Grant No.2005CB321703)Hunan Provincial Natural Science Foundation of China (Grant No.10JJ3021)Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province
文摘A kind of compressible miscible displacement problems which include molecular diffusion and dispersion in porous media are investigated.A symmetric interior penalty discontinuous Galerkin (SIPG) method is applied to the coupled system of flow and transport.Using the induction hypotheses instead of the cut-off operator and the interpolation projection properties,a priori hp error estimates are presented.The error bounds in L2(H1) norm for concentration and in L∞(L2) norm for velocity are optimal in h and suboptimal in p with a loss of power 1/2.
文摘Under the assumptions of nonlinear finite element and △t=o(h),Ewing and Wheeler discussed a Galerkin method for the single phase incompressible miscible displacement of one fluid by another in porous media.In the present paper we give a finite element scheme which weakens the △t=o(h)-restriction to △t=o(h~ε),0<ε≤1/2.Furthermore,this scheme is suitable for both linear element and nonlinear element.We also derive the optimal approximation estimates for concentration c,its gradient ▽c and the gradient ▽p of the pressure p.
基金Natural Science Foundation of Guangdong province,China(2018A0303100016)Educational Commission of Guangdong Province,China(2019KTSCX174)+1 种基金The second author's work is supported by the State Key Program of National Natural Science Foundation of China(11931003)National Natural Science Foundation of China(41974133,11671157).
文摘A nonlinear parabolic system is derived to describe compressible miscible displacement in a porous medium.The concentration equation is treated by a mixed finite element method with characteristics(CMFEM)and the pressure equation is treated by a parabolic mixed finite element method(PMFEM).Two-grid algorithm is considered to linearize nonlinear coupled system of two parabolic partial differential equations.Moreover,the L q error estimates are conducted for the pressure,Darcy velocity and concentration variables in the two-grid solutions.Both theoretical analysis and numerical experiments are presented to show that the two-grid algorithm is very effective.
基金supported by National Natural Science Foundation of China(Grant No.11101431)the Fundamental Research Funds for the Central Universities
文摘A combined method consisting of the mixed finite element method for flow and the local discontinuous Galerkin method for transport is introduced for the one-dimensional coupled system of incompressible miscible displacement problem. Optimal error estimates in L∞(0,T;L2) for concentration c,in L2(0,T;L2)for cxand L∞(0,T;L2) for velocity u are derived. The main technical difficulties in the analysis include the treatment of the inter-element jump terms which arise from the discontinuous nature of the numerical method,the nonlinearity,and the coupling of the models. Numerical experiments are performed to verify the theoretical results. Finally,we apply this method to the one-dimensional compressible miscible displacement problem and give the numerical experiments to confirm the efficiency of the scheme.
文摘The incompressible miscible displacement problem in porous media is modeled by a coupled system of two nonlinear partial differential equations,the pressure–velocity equation and the concentration equation.In this paper,we present a mixed finite volume element method(FVEM)for the approximation of the pressure–velocity equation and a standard FVEM for the concentration equation.A priori error estimates in L^(∞)(L^(2))are derived for velocity,pressure and concentration.Numerical results are presented to substantiate the validity of the theoretical results.
