In order to build a model for the Chang-8 low permeability sandstone reservoir in the Yanchang formation of the Xifeng oil field,we studied sedimentation and diagenesis of sandstone and analyzed major factors controll...In order to build a model for the Chang-8 low permeability sandstone reservoir in the Yanchang formation of the Xifeng oil field,we studied sedimentation and diagenesis of sandstone and analyzed major factors controlling this low permeability reservoir.By doing so,we have made clear that the spatial distribution of reservoir attribute parameters is controlled by the spatial distribution of various kinds of sandstone bodies.By taking advantage of many coring wells and high quality logging data,we used regression analysis for a single well with geological conditions as constraints,to build the interpretation model for logging data and to calculate attribute parameters for a single well,which ensured accuracy of the 1-D vertical model.On this basis,we built a litho-facies model to replace the sedimentary facies model.In addition,we also built a porosity model by using a sequential Gaussian simulation with the lithofacies model as the constraint.In the end,we built a permeability model by using Markov-Bayes simula-tion,with the porosity attribute as the covariate.The results show that the permeability model reflects very well the relative differences between low permeability values,which is of great importance for locating high permeability zones and forecasting zones favorable for exploration and exploitation.展开更多
The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid ...The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.展开更多
Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the c...Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the complicated phase behavior and various multiphase flow characteristics,gas tends to break through early in production wells in heterogeneous formations because of overriding,fingering,and channeling,which may result in unfavorable recovery performance.On the basis of phase behavior studies,minimum miscibility pressure measurements,and immiscible WAG coreflood experiments,the cubic B-spline model（CBM） was employed to describe the three-phase relative permeability curve.Using the Levenberg-Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially,optimization of production performance including pressure drop,water cut,and the cumulative gas-oil ratio was performed.A novel numerical inversion method was established for estimation of the water-oil-gas relative permeability curve during the immiscible WAG process.Based on the quantitative characterization of major recovery mechanisms,the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment.The proposed method is reliable and can meet engineering requirements.It provides a basic calculation theory for implicit estimation of oil-water-gas relative permeability curve.展开更多
Extraction of uranium from low-permeability sandstone is a long-standing challenge in mining.The improvement of sandstone permeability has therefore become a key research focus to improve the uranium leaching effect.T...Extraction of uranium from low-permeability sandstone is a long-standing challenge in mining.The improvement of sandstone permeability has therefore become a key research focus to improve the uranium leaching effect.To address the low-permeability problem and corresponding leaching limits,leaching experiments are performed using newly developed equipment that could apply low-frequency vibration to the sandstone samples.The test results indicate that low-frequency vibration significantly improves the uranium leaching performance and permeability of the sandstone samples.The leaching effect of low-frequency vibration treatment is approximately nine times more effective than ultrasonic vibration treatment,whereas the concentration of uranium ions generated without vibration treatment is not detectable.Mathematical model that considers the combined action of physico-mechanical vibration and chemical erosion is established to describe the effect of low-frequency vibration on the permeability.The calculated results are in good agreement with the tested permeability values.This study thus offers a new method to effectively leach more uranium from low-permeability sandstone using CO_(2)+O_(2)and provides an insight into the impact of low-frequency vibration on the uranium leaching process.展开更多
In order to solve the problem that sweat flows back into the internal layer from the external layer in double-layer knits, a fabric structure model is set up and the conditions that keep the sweat from flowing back in...In order to solve the problem that sweat flows back into the internal layer from the external layer in double-layer knits, a fabric structure model is set up and the conditions that keep the sweat from flowing back into the internal layer from the external layer are presented. It can be used to improve the design of the double-layer knits theoretically.展开更多
Research on the permeability and pressure distribution characteristics of the roadway surrounding rock in the excavation damaged zone(EDZ) is beneficial for the development of gas control technology. In this study, an...Research on the permeability and pressure distribution characteristics of the roadway surrounding rock in the excavation damaged zone(EDZ) is beneficial for the development of gas control technology. In this study, analytical solutions of stress and strain of the roadway surrounding rock were obtained, in which the creep deformation and strain softening were considered. Using the MTS815 rock mechanics testing system and a gas permeability testing system, permeability tests were conducted in the complete stress-strain process, and the evolution characteristics of permeability and strain were studied over the whole loading process. Based on the analytical solutions of stress and strain and the governing equation of gas seepage flow, this paper proposes a hydro-mechanical(HM) model, which considers three different zones around the roadway. Then the gas flow process in the roadway surrounding rock in three different zones was simulated according to the engineering geological conditions, thus obtaining the permeability and pressure distribution characteristics of the roadway surrounding rock in three different zones. These results show that the surrounding rock around the roadway can be divided into four regions-the full flow zone(FFZ), flow-shielding zone(FSZ), transitive flow zone(TFZ), and in-situ rock flow zone(IRFZ). These results could provide theoretical guidance for the improvement of gas extraction and gas control technology.展开更多
The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling directi...The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling direction. The hard magnetization direction was found at an angle of 60° to the rolling direction. To compare the measured and fitting curves, when the magnetic field intensity is higher than 7000 A/m, it is appropriate to simulate the relation of magnetic permeability and magnetization angle using the conventional elliptical model. When the magnetic field intensity is less than 3000 A/m, parabolic fitting models should be used; but when the magnetic field intensity is between 3000 and 7000 A/m, hybrid models with high accuracy, as proposed in this paper, should be applied. Piecewise relation models of magnetic permeability and magnetization angle are significant for improving the accuracy of electromagnetic engineering calculations of electrical steel, and these new models could be applied in further industrial applications.展开更多
Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of bi...Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory investigation.First,a gas permeability model was developed for vegetated coarse-grained soils with biochar addition.Then,a well-instrumented laboratory column test and two tests from the literature,considering bare,grass,biochar and grass+biochar conditions,were used for model validation.Finally,a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission rate.Results showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of saturation.The lowest water retention capacity,the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed column.However,adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability,resulting in the lowest gas emission rate.The measured gas emission rates for the four cases meet the recommended value by the design guideline.The parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170%in the grass case but decreased by 97%in the grass+biochar case.Under the severe drought condition with soil suction around 500 kPa,the gas emission rate in the grassed case exceeded the design value by 18%,while those in the biochar cases were far below the allowable value.Therefore,peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions.展开更多
The CO_2 permeability of fractured coal is of great significance to both coalbed gas extraction and CO_2 storage in coal seams, but the effects of high confining pressure, high injection pressure and elevated temperat...The CO_2 permeability of fractured coal is of great significance to both coalbed gas extraction and CO_2 storage in coal seams, but the effects of high confining pressure, high injection pressure and elevated temperature on the CO_2 permeability of fractured coal with different fracture extents have not been investigated thoroughly. In this paper, the CO_2 permeability of fractured coals sampled from a Pingdingshan coal mine in China and artificially fractured to a certain extent is investigated through undrained triaxial tests. The CO_2 permeability is measured under the confining pressure with a range of 10–25 MPa, injection pressure with a range of 6–12 MPa and elevated temperature with a range of 25–70°C. A mechanistic model is then proposed to characterize the CO_2 permeability of the fractured coals. The effects of thermal expansion, temperature-induced reduction of adsorption capacity, and thermal micro-cracking on the CO_2 permeability are explored. The test results show that the CO_2 permeability of naturally fractured coal saliently increases with increasing injection pressure. The increase of confining pressure reduces the permeability of both naturally fractured coal and secondarily fractured coal. It is also observed that initial fracturing by external loads can enhance the permeability, but further fracturing reduces the permeability. The CO_2 permeability decreases with the elevation of temperature if the temperature is lower than 44°C, but the permeability increases with temperature once the temperature is beyond 44°C. The mechanistic model well describes these compaction mechanisms induced by confining pressure, injection pressure and the complex effects induced by elevated temperature.展开更多
This work highlights the application of Artificial Neural Networks optimized by Cuckoo optimization algorithm for predictions of NMR log parameters including porosity and permeability by using field log data.The NMR l...This work highlights the application of Artificial Neural Networks optimized by Cuckoo optimization algorithm for predictions of NMR log parameters including porosity and permeability by using field log data.The NMR logging data have some highly vital privileges over conventional ones.The measured porosity is independent from bearer pore fluid and is effective porosity not total.Moreover,the permeability achieved by exact measurement and calculation considering clay content and pore fluid type.Therefore availability of the NMR data brings a great leverage in understanding the reservoir properties and also perfectly modelling the reservoir.Therefore,achieving NMR logging data by a model fed by a far inferior and less costly conventional logging data is a great privilege.The input parameters of model were neutron porosity(NPHI),sonic transit time(DT),bulk density(RHOB)and electrical resistivity(RT).The outputs of model were also permeability and porosity values.The structure developed model was build and trained by using train data.Graphical and statistical validation of results showed that the developed model is effective in prediction of field NMR log data.Outcomes show great possibility of using conventional logging data be used in order to reach the precious NMR logging data without any unnecessary costly tests for a reservoir.Moreover,the considerable accuracy of newly ANN-Cuckoo method also demonstrated.This study can be an illuminator in areas of reservoir engineering and modelling studies were presence of accurate data must be essential.展开更多
The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and...The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and Glass Beads are investigated and discussed in terms of the relative permeability,capillarity,and heterogeneity of the material on saturation rate of a reservoir.In the present model,the comparison of saturation level for different time and distance level have been discussed between homogeneous and heterogeneous porous medium for various types of sands.The reduced differential transform method(RDTM)is used to obtain approximate analytical solution of the proposed model.Numerical and graphical results are presented for a wide range of time and distance.展开更多
基金Project 50374048 supported by the National Natural Science Foundation of China
文摘In order to build a model for the Chang-8 low permeability sandstone reservoir in the Yanchang formation of the Xifeng oil field,we studied sedimentation and diagenesis of sandstone and analyzed major factors controlling this low permeability reservoir.By doing so,we have made clear that the spatial distribution of reservoir attribute parameters is controlled by the spatial distribution of various kinds of sandstone bodies.By taking advantage of many coring wells and high quality logging data,we used regression analysis for a single well with geological conditions as constraints,to build the interpretation model for logging data and to calculate attribute parameters for a single well,which ensured accuracy of the 1-D vertical model.On this basis,we built a litho-facies model to replace the sedimentary facies model.In addition,we also built a porosity model by using a sequential Gaussian simulation with the lithofacies model as the constraint.In the end,we built a permeability model by using Markov-Bayes simula-tion,with the porosity attribute as the covariate.The results show that the permeability model reflects very well the relative differences between low permeability values,which is of great importance for locating high permeability zones and forecasting zones favorable for exploration and exploitation.
基金supported by the National Nature Science Foundation of China(No.51278383,No.51238009 and No.51025827)Key Scientific and Technological Innovation Team of Zhejiang Province(No.2011R50020)Key Scientific and Technological Innovation Team of Wenzhou(No.C20120006)
文摘The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.
基金the financial support of the Important National Science and Technology Specific Projects of China (Grant No. 2011ZX05010-002)the Important Science and Technology Specific Projects of Petro China (Grant No. 2014E-3203)
文摘Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the complicated phase behavior and various multiphase flow characteristics,gas tends to break through early in production wells in heterogeneous formations because of overriding,fingering,and channeling,which may result in unfavorable recovery performance.On the basis of phase behavior studies,minimum miscibility pressure measurements,and immiscible WAG coreflood experiments,the cubic B-spline model（CBM） was employed to describe the three-phase relative permeability curve.Using the Levenberg-Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially,optimization of production performance including pressure drop,water cut,and the cumulative gas-oil ratio was performed.A novel numerical inversion method was established for estimation of the water-oil-gas relative permeability curve during the immiscible WAG process.Based on the quantitative characterization of major recovery mechanisms,the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment.The proposed method is reliable and can meet engineering requirements.It provides a basic calculation theory for implicit estimation of oil-water-gas relative permeability curve.
基金sponsored by the National Natural Science Foundation of China (Grant No. 11705086)Natural Science Foundation of Hunan Province (Grant No. 2018JJ3424)Fund of Hunan Provincial Department of Education (Grant No. 16C1387)
文摘Extraction of uranium from low-permeability sandstone is a long-standing challenge in mining.The improvement of sandstone permeability has therefore become a key research focus to improve the uranium leaching effect.To address the low-permeability problem and corresponding leaching limits,leaching experiments are performed using newly developed equipment that could apply low-frequency vibration to the sandstone samples.The test results indicate that low-frequency vibration significantly improves the uranium leaching performance and permeability of the sandstone samples.The leaching effect of low-frequency vibration treatment is approximately nine times more effective than ultrasonic vibration treatment,whereas the concentration of uranium ions generated without vibration treatment is not detectable.Mathematical model that considers the combined action of physico-mechanical vibration and chemical erosion is established to describe the effect of low-frequency vibration on the permeability.The calculated results are in good agreement with the tested permeability values.This study thus offers a new method to effectively leach more uranium from low-permeability sandstone using CO_(2)+O_(2)and provides an insight into the impact of low-frequency vibration on the uranium leaching process.
文摘In order to solve the problem that sweat flows back into the internal layer from the external layer in double-layer knits, a fabric structure model is set up and the conditions that keep the sweat from flowing back into the internal layer from the external layer are presented. It can be used to improve the design of the double-layer knits theoretically.
基金financially supported by the Natural Science Foundation of Jiangsu Province,China(No.BK20140189)the Postdoctoral Science Foundation of China(No.2014M550315)
文摘Research on the permeability and pressure distribution characteristics of the roadway surrounding rock in the excavation damaged zone(EDZ) is beneficial for the development of gas control technology. In this study, analytical solutions of stress and strain of the roadway surrounding rock were obtained, in which the creep deformation and strain softening were considered. Using the MTS815 rock mechanics testing system and a gas permeability testing system, permeability tests were conducted in the complete stress-strain process, and the evolution characteristics of permeability and strain were studied over the whole loading process. Based on the analytical solutions of stress and strain and the governing equation of gas seepage flow, this paper proposes a hydro-mechanical(HM) model, which considers three different zones around the roadway. Then the gas flow process in the roadway surrounding rock in three different zones was simulated according to the engineering geological conditions, thus obtaining the permeability and pressure distribution characteristics of the roadway surrounding rock in three different zones. These results show that the surrounding rock around the roadway can be divided into four regions-the full flow zone(FFZ), flow-shielding zone(FSZ), transitive flow zone(TFZ), and in-situ rock flow zone(IRFZ). These results could provide theoretical guidance for the improvement of gas extraction and gas control technology.
基金financially supported by of the National Natural Science Foundation of China(Nos.51174057 and 51274062)the National High Technology Research and Development Program of China(No.2012AA03A503)the Research Fund for the Doctoral Program of Higher Education of China(No.20130042110040)
文摘The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling direction. The hard magnetization direction was found at an angle of 60° to the rolling direction. To compare the measured and fitting curves, when the magnetic field intensity is higher than 7000 A/m, it is appropriate to simulate the relation of magnetic permeability and magnetization angle using the conventional elliptical model. When the magnetic field intensity is less than 3000 A/m, parabolic fitting models should be used; but when the magnetic field intensity is between 3000 and 7000 A/m, hybrid models with high accuracy, as proposed in this paper, should be applied. Piecewise relation models of magnetic permeability and magnetization angle are significant for improving the accuracy of electromagnetic engineering calculations of electrical steel, and these new models could be applied in further industrial applications.
基金Fundamental Research Funds for the Central Universities(Grant No.3221002220A1)State Key Laboratory of Subtropical Building Science in South China University of Technology(Grant No.2022ZC01).
文摘Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely studied.This study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory investigation.First,a gas permeability model was developed for vegetated coarse-grained soils with biochar addition.Then,a well-instrumented laboratory column test and two tests from the literature,considering bare,grass,biochar and grass+biochar conditions,were used for model validation.Finally,a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission rate.Results showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of saturation.The lowest water retention capacity,the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed column.However,adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability,resulting in the lowest gas emission rate.The measured gas emission rates for the four cases meet the recommended value by the design guideline.The parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170%in the grass case but decreased by 97%in the grass+biochar case.Under the severe drought condition with soil suction around 500 kPa,the gas emission rate in the grassed case exceeded the design value by 18%,while those in the biochar cases were far below the allowable value.Therefore,peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.51374213&51674251)the State Key Research Development Program of China(Grant No.2016YFC0600705)+3 种基金the National Natural Science Fund for Distinguished Young Scholars(Grant No.51125017)Fund for Creative Research and Development Group Program of Jiangsu Province(Grant No.2014-27)Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51421003)the State Key Research Development Program of China(Grant No.2016YFC0600705)
文摘The CO_2 permeability of fractured coal is of great significance to both coalbed gas extraction and CO_2 storage in coal seams, but the effects of high confining pressure, high injection pressure and elevated temperature on the CO_2 permeability of fractured coal with different fracture extents have not been investigated thoroughly. In this paper, the CO_2 permeability of fractured coals sampled from a Pingdingshan coal mine in China and artificially fractured to a certain extent is investigated through undrained triaxial tests. The CO_2 permeability is measured under the confining pressure with a range of 10–25 MPa, injection pressure with a range of 6–12 MPa and elevated temperature with a range of 25–70°C. A mechanistic model is then proposed to characterize the CO_2 permeability of the fractured coals. The effects of thermal expansion, temperature-induced reduction of adsorption capacity, and thermal micro-cracking on the CO_2 permeability are explored. The test results show that the CO_2 permeability of naturally fractured coal saliently increases with increasing injection pressure. The increase of confining pressure reduces the permeability of both naturally fractured coal and secondarily fractured coal. It is also observed that initial fracturing by external loads can enhance the permeability, but further fracturing reduces the permeability. The CO_2 permeability decreases with the elevation of temperature if the temperature is lower than 44°C, but the permeability increases with temperature once the temperature is beyond 44°C. The mechanistic model well describes these compaction mechanisms induced by confining pressure, injection pressure and the complex effects induced by elevated temperature.
文摘This work highlights the application of Artificial Neural Networks optimized by Cuckoo optimization algorithm for predictions of NMR log parameters including porosity and permeability by using field log data.The NMR logging data have some highly vital privileges over conventional ones.The measured porosity is independent from bearer pore fluid and is effective porosity not total.Moreover,the permeability achieved by exact measurement and calculation considering clay content and pore fluid type.Therefore availability of the NMR data brings a great leverage in understanding the reservoir properties and also perfectly modelling the reservoir.Therefore,achieving NMR logging data by a model fed by a far inferior and less costly conventional logging data is a great privilege.The input parameters of model were neutron porosity(NPHI),sonic transit time(DT),bulk density(RHOB)and electrical resistivity(RT).The outputs of model were also permeability and porosity values.The structure developed model was build and trained by using train data.Graphical and statistical validation of results showed that the developed model is effective in prediction of field NMR log data.Outcomes show great possibility of using conventional logging data be used in order to reach the precious NMR logging data without any unnecessary costly tests for a reservoir.Moreover,the considerable accuracy of newly ANN-Cuckoo method also demonstrated.This study can be an illuminator in areas of reservoir engineering and modelling studies were presence of accurate data must be essential.
文摘The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and Glass Beads are investigated and discussed in terms of the relative permeability,capillarity,and heterogeneity of the material on saturation rate of a reservoir.In the present model,the comparison of saturation level for different time and distance level have been discussed between homogeneous and heterogeneous porous medium for various types of sands.The reduced differential transform method(RDTM)is used to obtain approximate analytical solution of the proposed model.Numerical and graphical results are presented for a wide range of time and distance.
