Although the slippage effect has been extensively studied,most of the previous studies focused on the impact of the slippage effect on apparent permeability within a low pore pressure range,resulting in the inability ...Although the slippage effect has been extensively studied,most of the previous studies focused on the impact of the slippage effect on apparent permeability within a low pore pressure range,resulting in the inability of matching the evolution of permeability in the remaining pressure range.In this paper,a new apparent permeability model that reveals the evolution of permeability under the combined action of effective stress and slippage in the full pore pressure range was proposed.In this model,both intrinsic permeability and slippage coefficient are stress dependent.Three experimental tests with pore pressure lower than 2 MPa and a test with pore pressure at about 10 MPa using cores from the same origin under constant confining stress and constant effective stress are conducted.By comparing experimental data and another apparent permeability model,we proved the fidelity of our newly developed model.Furthermore,the contribution factor of the slippage effect Rslip is used to determine the low pore pressure limit with significant slippage effect.Our results show that both narrow initial pore size and high effective stress increase the critical pore pressure.Finally,the evolutions of the slippage coefficient and the intrinsic permeability under different boundary conditions were analyzed.展开更多
t Taking the M2 wave as calibration signals, we extract the phase shifts of the water level relative to the Earth tide in the Zhouzhi well by utilizing the cross-correlation function. And we further obtain the apparen...t Taking the M2 wave as calibration signals, we extract the phase shifts of the water level relative to the Earth tide in the Zhouzhi well by utilizing the cross-correlation function. And we further obtain the apparent permeability variation in the aquifer of the Zhouzhi well in 2008. Comparison with the commonly used tidal analysis software Baytap-G shows that phase shifts obtained by cross-correlation function are more stable. The resulting apparent permeability of the Zhouzhi well aquifer fluctuates with time, indicating it is a dynamically controlled parameter. The 2008 Wenchuan earthquake caused the apparent permeability increasing drastically, which is interpreted as the combination effects of effective stress changes and the barriers removing in the flow channel due to seismic wave pressure pulse. After the Wenchuan earthquake, the effective stress began to recover and the impurities deposited gradually, causing the apparent permeability to decrease a month later and almost recover to the pre-earthquake level in six months.展开更多
Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering m...Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.展开更多
Oil transport is greatly affected by heterogeneous pore–throat structures present in shale.It is therefore very important to accurately characterize pore–throat structures.Additionally,it remains unclear how pore–t...Oil transport is greatly affected by heterogeneous pore–throat structures present in shale.It is therefore very important to accurately characterize pore–throat structures.Additionally,it remains unclear how pore–throat structures affect oil transport capacity.In this paper,using finite element(FE)simulation and mathematical modeling,we calculated the hydrodynamic resistance for four pore–throat structure.In addition,the influence of pore throat structure on shale oil permeability is analyzed.According to the results,the hydrodynamic resistance of different pore throat structures can vary by 300%.The contribution of additional resistance caused by streamline bending is also in excess of 40%,even without slip length.Fur-thermore,Pore–throat structures can affect apparent permeability by more than 60%on the REV scale,and this influence increases with heterogeneity of pore size distribution,organic matter content,and organic matter number.Clearly,modeling shale oil flow requires consideration of porous–throat structure and additional resistance,otherwise oil recovery and flow capacity may be overestimated.展开更多
In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results ...In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results may not reflect the real situations.In this paper,a new apparent permeability model suitable for the shale gas of real state was developed by seepage mechanics method.In this model,the influential factors(e.g.the viscous flow and Knudsen diffusion of free gas and the surface diffusion of adsorbed gas)are taken into account to present the real flowing situations of shale gas in nanopores.Then,the accuracy of this new apparent permeability model was verified by comparing its calculation results with the experimental data.Finally,all factors influencing the apparent permeability of shale gas were analyzed in this new model.It is shown that the apparent permeability of shale gas is most affected by pressure and pore radius,and less by relative molecular mass and blockage coefficient.Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat mainly affect the fraction of permeability contributed by surface diffusion.Besides,the effects of each factor on apparent permeability and permeability fraction under low pressure are different from those under high pressure.Under low pressure,the effects of temperature and pore radius on apparent permeability are more obvious,and the effects of temperature,pore radius,Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat on the fraction of permeability are also more obvious.Finally,when the pressure is low and the pore radius is small,the surface diffusion is dominant.When the pressure is high and the pore radius is large,the viscous flow is dominant.In the case of small pore radius or low pressure,the surface diffusion shall not be neglected.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
A high sensitive method based on liquid chromatography tandem mass spectrometry（LC-MS/MS） was developed and validated for the study of permeability of danshensu（DS） and paeoniflorin（PF） in Caco-2 intestinal abso...A high sensitive method based on liquid chromatography tandem mass spectrometry（LC-MS/MS） was developed and validated for the study of permeability of danshensu（DS） and paeoniflorin（PF） in Caco-2 intestinal absorption model. The DS and PF were extracted from cell culture by vacuum-lyophilizing and then separated on a Zorbax Stable Bond C18 column with 0.1% acetic acid aqueous solution and methanol as mobile phase. Detection was carried out by negative electrospray ionization（ESI ） with selected reaction monitoring（SRM） mode. The apparent permeability coefficients（Papp） of DS and PF in Caco-2 cell medium were calculated and the effects of verapamil on the coefficients Papp of the two test compounds were also illustrated. The permeability of PF was much better than that of DS when the two compounds were administrated individually. Co-administration of DS and PF led to the decrease of the transport from apical side to basolateral side for both the compounds. However, the transport in the contrary direction were accelerated. It was also observed that verapamil could accelerate the transport of the test compounds from apical side to basolateral side. However, the absorption-enhanced effect of verapamil was attenuated when DS and PF were co-administrated. These observations suggest that both passive diffusion and active efflux involved in P-gp would effect the passage of DS and PF across Caco-2 cell monolayer. At the same time, the co-administration of DS and PF to an alteration of transport behavior, which suggests that the interaction must be taken into account when ‘n-in-one＇ samples were used in Caco-2 intestinal model.展开更多
The evolution due to temperature and pressure of shale reservoir permeability affects the productivity evaluation and development decision of shale gas reservoirs,which is very important for the exploration and develo...The evolution due to temperature and pressure of shale reservoir permeability affects the productivity evaluation and development decision of shale gas reservoirs,which is very important for the exploration and development of unconventional gas reservoirs.This study analyzed the coupling effects of temperature(25,50,and 75°C),effective stress(15 and 30 MPa),and pore pressure(0.5,2.0,4.0,and 8.0 MPa)on the permeability of the shale sample in the Longmaxi Formation.As the temperature and pressure increased,the apparent permeability exhibited a downward trend,and the absolute permeability decreased with the rise of temperature or effective stress.An in‐depth analysis of the gas slippage factors under the conditions of different temperature and pressure was conducted to evaluate the trend of the average pore width with temperature and pressure.The results were then verified by scanning electron microscopy(SEM).The results provide new insights into evaluating the permeability of the Longmaxi shale and can be used to enhance the gas recovery rate of deep shale gas reservoirs.展开更多
AIM: To study the absorption properties and mechanism of two important components, trolline and veratric acid, from the flowers of Trollius chinensis, in order to better understand the contribution of these two compou...AIM: To study the absorption properties and mechanism of two important components, trolline and veratric acid, from the flowers of Trollius chinensis, in order to better understand the contribution of these two compounds to the effectiveness of these flowers. METHOD: The human Caco-2 cell monolayer model was employed to study the transport of trolline and veratric acid from apical side(AP) to basal side(BL), and from BL to AP by determining the transport rates as the function of time and concentration and calculating apparent permeability coefficients(Papp). RESULTS: Trolline and veratric acid were transported across Caco-2 cell monolayer through different mechanisms in a concentration dependent manner.Trolline was transported at a Papp level of 10-6 cm·s-1 with a Papp AP→BL/Papp BL→AP ratio of more than 1.8 or less than 0.8, while veratric acid was transported at a Papp level of 10-5 cm·s-1 with a Papp AP→BL/Papp BL→AP ratio of close to 1.0. CONCLUSION: Trolline is moderately absorbed through an associative mechanism involving active and passive transport, and veratric acid is well-absorbed mainly through passive diffusion. These factors should be taken into account when chemically assessing the pharmacodynamic material basis of the flowers of T. chinensis.展开更多
Objective This study was conducted to examine the absorption and translocation of conjugated bile acids(BAs)in Calculus bovis and its substitutes to detect differences in these materials.Methods A Caco-2 monolayer cel...Objective This study was conducted to examine the absorption and translocation of conjugated bile acids(BAs)in Calculus bovis and its substitutes to detect differences in these materials.Methods A Caco-2 monolayer cell model was used to compare the apparent permeability coefficient(Papp)value and efflux ratio(ER)of BAs in natural cow-bezoar(NCB),artificial cow-bezoar(ACB),and in vitro cultured cow-bezoar(Ivt-CCB).Papp and ER values were determined by liquid chromatography-mass spectrometry.Samples were separated on an analytical column.Results The distribution of BAs in NCB was significantly different from that in ACB and Ivt-CCB.The percentages of conjugated BAs were significantly higher in NCB than in the two substitutes.The distribution differences of conjugated and unconjugated BAs can be used to distinguish costly NCB from relatively inexpensive substitutes.Conclusion The transport characteristics of BAs in Ivt-CCB were more consistent with NCB than with ACB,even when the proportions of BAs in Ivt-CCB were closer to those of ACB.展开更多
Using the typical characteristics of multi-layered marine and continental transitional gas reservoirs as a basis,a model is developed to predict the related well production rate.This model relies on the fractal theory...Using the typical characteristics of multi-layered marine and continental transitional gas reservoirs as a basis,a model is developed to predict the related well production rate.This model relies on the fractal theory of tortuous capillary bundles and can take into account multiple gas flow mechanisms at the micrometer and nanometer scales,as well as the flow characteristics in different types of thin layers(tight sandstone gas,shale gas,and coalbed gas).Moreover,a source-sink function concept and a pressure drop superposition principle are utilized to introduce a coupled flow model in the reservoir.A semi-analytical solution for the production rate is obtained using a matrix iteration method.A specific well is selected for fitting dynamic production data,and the calculation results show that the tight sandstone has the highest gas production per unit thickness compared with the other types of reservoirs.Moreover,desorption and diffusion of coalbed gas and shale gas can significantly contribute to gas production,and the daily production of these two gases decreases rapidly with decreasing reservoir pressure.Interestingly,the gas production from fractures exhibits an approximately U-shaped distribution,indicating the need to optimize the spacing between clusters during hydraulic fracturing to reduce the area of overlapping fracture control.The coal matrix water saturation significantly affects the coalbed gas production,with higher water saturation leading to lower production.展开更多
Gas sorption and non-Darcy flow are two important issues for shale gas reservoirs. The sorption consists of dissolution and adsorption. Dissolved gas and adsorbed gas are different. The former is dissolved in the shal...Gas sorption and non-Darcy flow are two important issues for shale gas reservoirs. The sorption consists of dissolution and adsorption. Dissolved gas and adsorbed gas are different. The former is dissolved in the shale matrix, while the latter is concentrated near the solid walls of pores. In this paper, the Langmuir equation is used to describe adsorption and Henry’s law is used to describe dissolution. The K coefficient in Henry’s law of 0.052 mmol/(MPa g TOC) is obtained by matching experimental data. The amount of dissolved gas increases linearly when pressure increases. Using only the Langmuir equation without considering dissolution can lead to a significant underestimation of the amount of sorbed gas in shales. For non-Darcy gas flow, the apparent permeability model for free gas is established by combining slip flow and Knudsen flow. For adsorbed gas, the surface diffusion effect is also considered in this model. The surface diffu- sion coefficient is suggested to be of the same scale as the gas self-diffusion coefficient, and the corresponding effective permeability is derived. When 1/ increases,k/ kincreases, but the relationship is not linear as the Klinkenberg effect suggests. The effect of adsorption on the gas flow is significant in nanopores (r≤2 nm). Adsorption increases apparent permeability in shales at low pressures and decreases it at high pressures.展开更多
Objective To study the intestinal absorption and transepithelial transport of three limoninoids: evodol (EVO), limonin (LIM), and shihulimonin A (SHIA), isolated from Fructus Evodiae [the unripe fruit of Evodia rutaec...Objective To study the intestinal absorption and transepithelial transport of three limoninoids: evodol (EVO), limonin (LIM), and shihulimonin A (SHIA), isolated from Fructus Evodiae [the unripe fruit of Evodia rutaecarpa and Evodia rutaecarpa var. bodinieri] in the human intestine. Methods The in vitro cultured human colon carcinoma cell line, Caco-2 cell monolayer model, was applied to studying the absorption and transepithelial transport of the three limoninoids from apical (AP) to basolateral (BL) side and from BL to AP side. The three limoninoids were measured by reversed-phase high performance liquid chromatography coupled with ultraviolet absorption detector. Transport parameters and apparent permeability coefficients (Papp) were then calculated and compared with those of Propranolol as a control substance of high permeability and Atenolol as a control substance of poor permeability. Results The Papp value of EVO and LIM from AP to BL side for absorption and transport were 1.78 × 10-5 cm/s and 1.16 × 10-5 cm/s, respectively, which was comparable to that of Propranolol with Papp 2.18 × 10-5 cm/s. Conclusion The absorption and transport of both EVO and LIM are main passive diffusion as the dominating process in Caco-2 cell monolayer model, and they were estimated to be high absorbed compounds. SHIA in Caco-2 cell monolayer model may be involved in metabolism in the transport processes.展开更多
Objective： To investigate the absorption and transport mechanism of magnolol in Caco-2 cell model. Methods： A human intestinal epithelial cell model Caco-2 cell in vitro cultured was applied to study the absorption ...Objective： To investigate the absorption and transport mechanism of magnolol in Caco-2 cell model. Methods： A human intestinal epithelial cell model Caco-2 cell in vitro cultured was applied to study the absorption and transport of magnolol, the effects of time, donor concentration, P-gp inhibitor verapamil, pH and temperature on the absorption and transport of magnolol were investigated. The determination of magnolol was performed by high performance liquid chromatography, then the values of apparent permeability coefficient （Papp） and Pratio Basolateral-to-Apical （BL-to-AP）/Apical-to-Basolateral （AP-to-BL） were calculated. Results： In Caco-2 cell model, comparing the amounts of transport of AP-to-BL and BL-to-AP, the latter was larger. At the same donor concentration, either the amounts of transport of AP-to-BL or BL-to-AP increased with increase in donor concentration and incubation time. Verapamil could significantly improve the amounts of transport of AP- to-BL. The transport of AP-to-BL and BL-to-AP depended on temperature, and there was no significant effect of pH on the transport of AP-to-BL. Conclusion： Magnolol could be transported through the intestinal mucosa via a passive diffusion mechanism primarily, coexisting with a carrier-mediated transport, at the same time, the efflux mechanism could be involved.展开更多
Gas transport mechanisms can be categorized into viscous flow and mass diffusion,both of which may coexist in a porous media with multiscale pore sizes.To determine the dominant transport mechanism and its contributio...Gas transport mechanisms can be categorized into viscous flow and mass diffusion,both of which may coexist in a porous media with multiscale pore sizes.To determine the dominant transport mechanism and its contribution to gas transport capacity,the gas viscous flow and mass diffusion processes are analyzed in single nanoscale pores via a theoretical method,and are simulated in 3D nanoporous media via pore-scale lattice Boltzmann methods.The apparent permeability from the viscous flow and apparent diffusivity from the mass diffusion are estimated.A dimensionless parameter,i.e.,the diffusion-flow ratio,is proposed to evaluate the dominant transport mechanism,which is a function of the apparent permeability,apparent diffusivity,bulk dynamic viscosity,and working pressure.The results show that the apparent permeability increases by approximately two orders of magnitude when the average Knudsen number(Kn_(avg))of the nanoporous media or Knudsen number(Kn)of single nanoscale pores increases from 0.1 to 10.Under the same conditions,the increment in the apparent diffusivity is only approximately one order of magnitude.When Kn<0.01,the apparent permeability has a lower bound(i.e.,absolute permeability).When Kn>10,the apparent diffusivity has an upper bound(i.e.,Knudsen diffusivity).The dominant transport mechanism in single nanoscale pores is the viscous flow for 0.01<Kn<100,where the maximum diffusion-flow ratio is less than one.In nanoporous media,the dominant transport relies heavily on Kn_(avg) and the structural parameters.For nanoporous media with the pore throat diameter of 3 nm,Kn_(avg)=0.2 is the critical point,above which the mass diffusion is dominant;otherwise,the viscous flow is dominant.As Kn_(avg) increases to 3.4,the mass diffusion is overwhelming,with the maximum diffusion-flow ratio reaching ~4.展开更多
基金supported by the National Natural Science Foundation of China(No.52079077)the Natural Science Foundation of Shandong Province(No.ZR2021QE069)China Postdoctoral Science Foundation(No.2019M662402).
文摘Although the slippage effect has been extensively studied,most of the previous studies focused on the impact of the slippage effect on apparent permeability within a low pore pressure range,resulting in the inability of matching the evolution of permeability in the remaining pressure range.In this paper,a new apparent permeability model that reveals the evolution of permeability under the combined action of effective stress and slippage in the full pore pressure range was proposed.In this model,both intrinsic permeability and slippage coefficient are stress dependent.Three experimental tests with pore pressure lower than 2 MPa and a test with pore pressure at about 10 MPa using cores from the same origin under constant confining stress and constant effective stress are conducted.By comparing experimental data and another apparent permeability model,we proved the fidelity of our newly developed model.Furthermore,the contribution factor of the slippage effect Rslip is used to determine the low pore pressure limit with significant slippage effect.Our results show that both narrow initial pore size and high effective stress increase the critical pore pressure.Finally,the evolutions of the slippage coefficient and the intrinsic permeability under different boundary conditions were analyzed.
基金supported by the National Natural Science Foundation of China under grant Nos.40674024 and 41040036
文摘t Taking the M2 wave as calibration signals, we extract the phase shifts of the water level relative to the Earth tide in the Zhouzhi well by utilizing the cross-correlation function. And we further obtain the apparent permeability variation in the aquifer of the Zhouzhi well in 2008. Comparison with the commonly used tidal analysis software Baytap-G shows that phase shifts obtained by cross-correlation function are more stable. The resulting apparent permeability of the Zhouzhi well aquifer fluctuates with time, indicating it is a dynamically controlled parameter. The 2008 Wenchuan earthquake caused the apparent permeability increasing drastically, which is interpreted as the combination effects of effective stress changes and the barriers removing in the flow channel due to seismic wave pressure pulse. After the Wenchuan earthquake, the effective stress began to recover and the impurities deposited gradually, causing the apparent permeability to decrease a month later and almost recover to the pre-earthquake level in six months.
基金the National Natural Science Foundation of China(Grant Nos.12102372 and 11872324)the Open Research Fund of CNMGE Platform&NSCC-TJ(Grant No.CNMGE2023011).
文摘Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.
基金supported by the National Natural Science Foundation of China(52274056,U22B2075).
文摘Oil transport is greatly affected by heterogeneous pore–throat structures present in shale.It is therefore very important to accurately characterize pore–throat structures.Additionally,it remains unclear how pore–throat structures affect oil transport capacity.In this paper,using finite element(FE)simulation and mathematical modeling,we calculated the hydrodynamic resistance for four pore–throat structure.In addition,the influence of pore throat structure on shale oil permeability is analyzed.According to the results,the hydrodynamic resistance of different pore throat structures can vary by 300%.The contribution of additional resistance caused by streamline bending is also in excess of 40%,even without slip length.Fur-thermore,Pore–throat structures can affect apparent permeability by more than 60%on the REV scale,and this influence increases with heterogeneity of pore size distribution,organic matter content,and organic matter number.Clearly,modeling shale oil flow requires consideration of porous–throat structure and additional resistance,otherwise oil recovery and flow capacity may be overestimated.
基金Project supported by the National Major Science and Technology Project“Research on Flow Mechanism and Numerical Simulation of Shale Oil in Chang 7 in South Hubei Province”(No.:2017ZX05049-006)the National Natural Science Foundation of China“Multi-scale Transport Mechanism and Numerical Simulation of Shale Oil”(No.:51674279).
文摘In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results may not reflect the real situations.In this paper,a new apparent permeability model suitable for the shale gas of real state was developed by seepage mechanics method.In this model,the influential factors(e.g.the viscous flow and Knudsen diffusion of free gas and the surface diffusion of adsorbed gas)are taken into account to present the real flowing situations of shale gas in nanopores.Then,the accuracy of this new apparent permeability model was verified by comparing its calculation results with the experimental data.Finally,all factors influencing the apparent permeability of shale gas were analyzed in this new model.It is shown that the apparent permeability of shale gas is most affected by pressure and pore radius,and less by relative molecular mass and blockage coefficient.Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat mainly affect the fraction of permeability contributed by surface diffusion.Besides,the effects of each factor on apparent permeability and permeability fraction under low pressure are different from those under high pressure.Under low pressure,the effects of temperature and pore radius on apparent permeability are more obvious,and the effects of temperature,pore radius,Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat on the fraction of permeability are also more obvious.Finally,when the pressure is low and the pore radius is small,the surface diffusion is dominant.When the pressure is high and the pore radius is large,the viscous flow is dominant.In the case of small pore radius or low pressure,the surface diffusion shall not be neglected.
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the National Basic Research Priorities Program of China(No. 2005CB523402)the Natural Science Foundation of Zhejiang Province,China(No.Y204418)the Program for New Century Excellent Talents in University of China (No.NCET-06-0515)
文摘A high sensitive method based on liquid chromatography tandem mass spectrometry（LC-MS/MS） was developed and validated for the study of permeability of danshensu（DS） and paeoniflorin（PF） in Caco-2 intestinal absorption model. The DS and PF were extracted from cell culture by vacuum-lyophilizing and then separated on a Zorbax Stable Bond C18 column with 0.1% acetic acid aqueous solution and methanol as mobile phase. Detection was carried out by negative electrospray ionization（ESI ） with selected reaction monitoring（SRM） mode. The apparent permeability coefficients（Papp） of DS and PF in Caco-2 cell medium were calculated and the effects of verapamil on the coefficients Papp of the two test compounds were also illustrated. The permeability of PF was much better than that of DS when the two compounds were administrated individually. Co-administration of DS and PF led to the decrease of the transport from apical side to basolateral side for both the compounds. However, the transport in the contrary direction were accelerated. It was also observed that verapamil could accelerate the transport of the test compounds from apical side to basolateral side. However, the absorption-enhanced effect of verapamil was attenuated when DS and PF were co-administrated. These observations suggest that both passive diffusion and active efflux involved in P-gp would effect the passage of DS and PF across Caco-2 cell monolayer. At the same time, the co-administration of DS and PF to an alteration of transport behavior, which suggests that the interaction must be taken into account when ‘n-in-one＇ samples were used in Caco-2 intestinal model.
基金National Natural Science Foundations of China,Grant/Award Numbers:51809264,52178375,52211530088Fundamental Research Funds for the Central Universities,Grant/Award Number:2023ZKPYLJ06。
文摘The evolution due to temperature and pressure of shale reservoir permeability affects the productivity evaluation and development decision of shale gas reservoirs,which is very important for the exploration and development of unconventional gas reservoirs.This study analyzed the coupling effects of temperature(25,50,and 75°C),effective stress(15 and 30 MPa),and pore pressure(0.5,2.0,4.0,and 8.0 MPa)on the permeability of the shale sample in the Longmaxi Formation.As the temperature and pressure increased,the apparent permeability exhibited a downward trend,and the absolute permeability decreased with the rise of temperature or effective stress.An in‐depth analysis of the gas slippage factors under the conditions of different temperature and pressure was conducted to evaluate the trend of the average pore width with temperature and pressure.The results were then verified by scanning electron microscopy(SEM).The results provide new insights into evaluating the permeability of the Longmaxi shale and can be used to enhance the gas recovery rate of deep shale gas reservoirs.
基金supported by the National Sciences Foundation of China(Nos.81073018,81274044)
文摘AIM: To study the absorption properties and mechanism of two important components, trolline and veratric acid, from the flowers of Trollius chinensis, in order to better understand the contribution of these two compounds to the effectiveness of these flowers. METHOD: The human Caco-2 cell monolayer model was employed to study the transport of trolline and veratric acid from apical side(AP) to basal side(BL), and from BL to AP by determining the transport rates as the function of time and concentration and calculating apparent permeability coefficients(Papp). RESULTS: Trolline and veratric acid were transported across Caco-2 cell monolayer through different mechanisms in a concentration dependent manner.Trolline was transported at a Papp level of 10-6 cm·s-1 with a Papp AP→BL/Papp BL→AP ratio of more than 1.8 or less than 0.8, while veratric acid was transported at a Papp level of 10-5 cm·s-1 with a Papp AP→BL/Papp BL→AP ratio of close to 1.0. CONCLUSION: Trolline is moderately absorbed through an associative mechanism involving active and passive transport, and veratric acid is well-absorbed mainly through passive diffusion. These factors should be taken into account when chemically assessing the pharmacodynamic material basis of the flowers of T. chinensis.
基金support from the Youth Development Research Foundation of NIFDC(2014A1)National Science and Technology Major Project(2017ZX09101002-002-008)the National Natural Science Foundation of China(No.81403171 and No.81603517)
文摘Objective This study was conducted to examine the absorption and translocation of conjugated bile acids(BAs)in Calculus bovis and its substitutes to detect differences in these materials.Methods A Caco-2 monolayer cell model was used to compare the apparent permeability coefficient(Papp)value and efflux ratio(ER)of BAs in natural cow-bezoar(NCB),artificial cow-bezoar(ACB),and in vitro cultured cow-bezoar(Ivt-CCB).Papp and ER values were determined by liquid chromatography-mass spectrometry.Samples were separated on an analytical column.Results The distribution of BAs in NCB was significantly different from that in ACB and Ivt-CCB.The percentages of conjugated BAs were significantly higher in NCB than in the two substitutes.The distribution differences of conjugated and unconjugated BAs can be used to distinguish costly NCB from relatively inexpensive substitutes.Conclusion The transport characteristics of BAs in Ivt-CCB were more consistent with NCB than with ACB,even when the proportions of BAs in Ivt-CCB were closer to those of ACB.
文摘Using the typical characteristics of multi-layered marine and continental transitional gas reservoirs as a basis,a model is developed to predict the related well production rate.This model relies on the fractal theory of tortuous capillary bundles and can take into account multiple gas flow mechanisms at the micrometer and nanometer scales,as well as the flow characteristics in different types of thin layers(tight sandstone gas,shale gas,and coalbed gas).Moreover,a source-sink function concept and a pressure drop superposition principle are utilized to introduce a coupled flow model in the reservoir.A semi-analytical solution for the production rate is obtained using a matrix iteration method.A specific well is selected for fitting dynamic production data,and the calculation results show that the tight sandstone has the highest gas production per unit thickness compared with the other types of reservoirs.Moreover,desorption and diffusion of coalbed gas and shale gas can significantly contribute to gas production,and the daily production of these two gases decreases rapidly with decreasing reservoir pressure.Interestingly,the gas production from fractures exhibits an approximately U-shaped distribution,indicating the need to optimize the spacing between clusters during hydraulic fracturing to reduce the area of overlapping fracture control.The coal matrix water saturation significantly affects the coalbed gas production,with higher water saturation leading to lower production.
基金supported by the Department of Energy under Award Number DE-FE0024311
文摘Gas sorption and non-Darcy flow are two important issues for shale gas reservoirs. The sorption consists of dissolution and adsorption. Dissolved gas and adsorbed gas are different. The former is dissolved in the shale matrix, while the latter is concentrated near the solid walls of pores. In this paper, the Langmuir equation is used to describe adsorption and Henry’s law is used to describe dissolution. The K coefficient in Henry’s law of 0.052 mmol/(MPa g TOC) is obtained by matching experimental data. The amount of dissolved gas increases linearly when pressure increases. Using only the Langmuir equation without considering dissolution can lead to a significant underestimation of the amount of sorbed gas in shales. For non-Darcy gas flow, the apparent permeability model for free gas is established by combining slip flow and Knudsen flow. For adsorbed gas, the surface diffusion effect is also considered in this model. The surface diffu- sion coefficient is suggested to be of the same scale as the gas self-diffusion coefficient, and the corresponding effective permeability is derived. When 1/ increases,k/ kincreases, but the relationship is not linear as the Klinkenberg effect suggests. The effect of adsorption on the gas flow is significant in nanopores (r≤2 nm). Adsorption increases apparent permeability in shales at low pressures and decreases it at high pressures.
基金supported partly by the Beijing Science Foundation (No. Z0004105040311)National High Technology Program (No. 2002AA2Z343C+2 种基金 No. 2004AA2Z3783)National Sciences and Technology Program (No. 2006BAI 06A01-02 No. 2006BAI08B03-09) of China
文摘Objective To study the intestinal absorption and transepithelial transport of three limoninoids: evodol (EVO), limonin (LIM), and shihulimonin A (SHIA), isolated from Fructus Evodiae [the unripe fruit of Evodia rutaecarpa and Evodia rutaecarpa var. bodinieri] in the human intestine. Methods The in vitro cultured human colon carcinoma cell line, Caco-2 cell monolayer model, was applied to studying the absorption and transepithelial transport of the three limoninoids from apical (AP) to basolateral (BL) side and from BL to AP side. The three limoninoids were measured by reversed-phase high performance liquid chromatography coupled with ultraviolet absorption detector. Transport parameters and apparent permeability coefficients (Papp) were then calculated and compared with those of Propranolol as a control substance of high permeability and Atenolol as a control substance of poor permeability. Results The Papp value of EVO and LIM from AP to BL side for absorption and transport were 1.78 × 10-5 cm/s and 1.16 × 10-5 cm/s, respectively, which was comparable to that of Propranolol with Papp 2.18 × 10-5 cm/s. Conclusion The absorption and transport of both EVO and LIM are main passive diffusion as the dominating process in Caco-2 cell monolayer model, and they were estimated to be high absorbed compounds. SHIA in Caco-2 cell monolayer model may be involved in metabolism in the transport processes.
基金Supported by the National Key Technology Program(No. 2006BAI11B08-04)
文摘Objective： To investigate the absorption and transport mechanism of magnolol in Caco-2 cell model. Methods： A human intestinal epithelial cell model Caco-2 cell in vitro cultured was applied to study the absorption and transport of magnolol, the effects of time, donor concentration, P-gp inhibitor verapamil, pH and temperature on the absorption and transport of magnolol were investigated. The determination of magnolol was performed by high performance liquid chromatography, then the values of apparent permeability coefficient （Papp） and Pratio Basolateral-to-Apical （BL-to-AP）/Apical-to-Basolateral （AP-to-BL） were calculated. Results： In Caco-2 cell model, comparing the amounts of transport of AP-to-BL and BL-to-AP, the latter was larger. At the same donor concentration, either the amounts of transport of AP-to-BL or BL-to-AP increased with increase in donor concentration and incubation time. Verapamil could significantly improve the amounts of transport of AP- to-BL. The transport of AP-to-BL and BL-to-AP depended on temperature, and there was no significant effect of pH on the transport of AP-to-BL. Conclusion： Magnolol could be transported through the intestinal mucosa via a passive diffusion mechanism primarily, coexisting with a carrier-mediated transport, at the same time, the efflux mechanism could be involved.
基金supported by the National Science Foundation for Distinguished Young Scholars(52025065)the China Scholarship Council(201906280349)for its financial support during her study at The University of Texas at Austin.
文摘Gas transport mechanisms can be categorized into viscous flow and mass diffusion,both of which may coexist in a porous media with multiscale pore sizes.To determine the dominant transport mechanism and its contribution to gas transport capacity,the gas viscous flow and mass diffusion processes are analyzed in single nanoscale pores via a theoretical method,and are simulated in 3D nanoporous media via pore-scale lattice Boltzmann methods.The apparent permeability from the viscous flow and apparent diffusivity from the mass diffusion are estimated.A dimensionless parameter,i.e.,the diffusion-flow ratio,is proposed to evaluate the dominant transport mechanism,which is a function of the apparent permeability,apparent diffusivity,bulk dynamic viscosity,and working pressure.The results show that the apparent permeability increases by approximately two orders of magnitude when the average Knudsen number(Kn_(avg))of the nanoporous media or Knudsen number(Kn)of single nanoscale pores increases from 0.1 to 10.Under the same conditions,the increment in the apparent diffusivity is only approximately one order of magnitude.When Kn<0.01,the apparent permeability has a lower bound(i.e.,absolute permeability).When Kn>10,the apparent diffusivity has an upper bound(i.e.,Knudsen diffusivity).The dominant transport mechanism in single nanoscale pores is the viscous flow for 0.01<Kn<100,where the maximum diffusion-flow ratio is less than one.In nanoporous media,the dominant transport relies heavily on Kn_(avg) and the structural parameters.For nanoporous media with the pore throat diameter of 3 nm,Kn_(avg)=0.2 is the critical point,above which the mass diffusion is dominant;otherwise,the viscous flow is dominant.As Kn_(avg) increases to 3.4,the mass diffusion is overwhelming,with the maximum diffusion-flow ratio reaching ~4.
