Increasing the allowable gas pressure of underground gas storage(UGS) is one of the most effective methods to increase its working gas capacity. In this context, hydraulic fracturing tests are implemented on the targe...Increasing the allowable gas pressure of underground gas storage(UGS) is one of the most effective methods to increase its working gas capacity. In this context, hydraulic fracturing tests are implemented on the target formation for the UGS construction of Jintan salt caverns, China, in order to obtain the minimum principal in situ stress and the fracture breakdown pressure. Based on the test results, the maximum allowable gas pressure of the Jintan UGS salt cavern is calibrated. To determine the maximum allowable gas pressure, KING-1 and KING-2 caverns are used as examples. A three-dimensional(3D)geomechanical model is established based on the sonar data of the two caverns with respect to the features of the target formation. New criteria for evaluating gas penetration failure and gas seepage are proposed. Results show that the maximum allowable gas pressure of the Jintan UGS salt cavern can be increased from 17 MPa to 18 MPa(i.e. a gradient of about 18 k Pa/m at the casing shoe depth). Based on numerical results, a field test with increasing maximum gas pressure to 18 MPa has been carried out in KING-1 cavern. Microseismic monitoring has been conducted during the test to evaluate the safety of the rock mass around the cavern. Field monitoring data show that KING-1 cavern is safe globally when the maximum gas pressure is increased from 17 MPa to 18 MPa. This shows that the geomechanical model and criteria proposed in this context for evaluating the maximum allowable gas pressure are reliable.展开更多
In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for ...In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for acquiring discontinuity measurements from 3D models,such as point clouds generated using laser scanning or photogrammetry.However,even with numerous automated and semiautomated methods presented in the literature,there is not one single method that can automatically characterize discontinuities accurately in a minimum of time.In this paper,we critically review all the existing methods proposed in the literature for the extraction of discontinuity characteristics such as joint sets and orientations,persistence,joint spacing,roughness and block size using point clouds,digital elevation maps,or meshes.As a result of this review,we identify the strengths and drawbacks of each method used for extracting those characteristics.We found that the approaches based on voxels and region growing are superior in extracting joint planes from 3D point clouds.Normal tensor voting with trace growth algorithm is a robust method for measuring joint trace length from 3D meshes.Spacing is estimated by calculating the perpendicular distance between joint planes.Several independent roughness indices are presented to quantify roughness from 3D surface models,but there is a need to incorporate these indices into automated methodologies.There is a lack of efficient algorithms for direct computation of block size from 3D rock mass surface models.展开更多
In this paper,a new micro-creep model of salt rock is proposed based on a linear parallel bonded model(LPBM)using the two-dimensional particle flow code(PFC2D).The power function weakening form is assumed to describe ...In this paper,a new micro-creep model of salt rock is proposed based on a linear parallel bonded model(LPBM)using the two-dimensional particle flow code(PFC2D).The power function weakening form is assumed to describe the variation of the parallel bonded diameter(PBD)over time.By comparing with the parallel-bonded stress corrosion(PSC)model,a smaller stress fluctuation and smoother creep strain−time curves can be obtained by this power function model at the same stress level.The validity and adaptability of the model to simulate creep deformation of salt rock are verified through comparing the laboratory creep test curves and the Burgers model fitting result.The numerical results reveal that this model can be capable of capturing the creep deformation and damage behavior from the laboratory observations.展开更多
A new dynamic model identification method is developed for continuous-time series analysis and forward prediction applications. The quantum of data is defined over moving time intervals in sliding window coordinates f...A new dynamic model identification method is developed for continuous-time series analysis and forward prediction applications. The quantum of data is defined over moving time intervals in sliding window coordinates for compressing the size of stored data while retaining the resolution of information. Quantum vectors are introduced as the basis of a linear space for defining a Dynamic Quantum Operator (DQO) model of the system defined by its data stream. The transport of the quantum of compressed data is modeled between the time interval bins during the movement of the sliding time window. The DQO model is identified from the samples of the real-time flow of data over the sliding time window. A least-square-fit identification method is used for evaluating the parameters of the quantum operator model, utilizing the repeated use of the sampled data through a number of time steps. The method is tested to analyze, and forward-predict air temperature variations accessed from weather data as well as methane concentration variations obtained from measurements of an operating mine. The results show efficient forward prediction capabilities, surpassing those using neural networks and other methods for the same task.展开更多
An analytical model, TA(t), for the observed outside air temperature change, Ta(t), with time is developed using two components: one for the variation caused by the Earth’s movement, plus any other quasi-stationary t...An analytical model, TA(t), for the observed outside air temperature change, Ta(t), with time is developed using two components: one for the variation caused by the Earth’s movement, plus any other quasi-stationary thermodynamic effects due to industrialization;and one for the random variation caused by stochastic and/or chaotic, local environmental changes. The first component, TR(t), describes a regular trend, expressed by periodic functions of time and constants unchanged with time. The second component, TS, is a random, stochastic variation. For the observed outside air temperature, the analytical model of TA(t)=TR(t) +TS is such as to give a statistically best approximation for the observed time period with = min. Several versions for the TR(t) functions are defined and tested in the study for an example location for 20 years. The best model for TR(t) t is found as a linear function with time plus a variable-coefficient Fourier series with linearly changing amplitude with time. It is found that the final analytical temperature, TA(t), can be used not only to represent the historical daily mean temperature but also to predict the future daily mean temperature at the given location. The upper and lower boundaries give safety limits for the temperature prediction. The stochastic component identified in the model is stable and stationary. The method of model identification for TA(t) can be used for determining input temperature functions for supporting engineering design;or for an unbiased scientific inquiry of temperature change with time in climate studies.展开更多
This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(...This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(LCA)study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate(HCL)and low-contaminated leachate(LCL).The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity.Also,oxalic acid,Na_(2)CO_(3),and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides(REOs),including solvent extraction(SX)and precipitation steps.The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H_(2)SO_(4)usage,so 468 and 292 kg of carbon dioxide are generated to produce1 t of individual REOs from HCL and LCL routes,respectively.Moreover,the carbon dioxide emitted from the process,including the RE-hydroxide production,SX,and REOs production,is less than 10 t CO_(2).A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process,as the main stage has a higher contribution to the whole process.This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process.展开更多
Graphene materials have drawn tremendous attention in recent years.The formation of holes and pores on graphene sheets can provide transfer channels and facilitate the ion/electron transport kinetics.In this study,gra...Graphene materials have drawn tremendous attention in recent years.The formation of holes and pores on graphene sheets can provide transfer channels and facilitate the ion/electron transport kinetics.In this study,graphene nanosheets were prepared electrochemically,and then,they were used as the starting material for the preparation of holey graphene(HG)through the KOH activation process.The weight ratio of initial electrochemically exfoliated graphene(EEG)to KOH was optimized according to the morphological features,BET surface area examination,graphene number of layers calculated from XRD patterns,and the ID/IG ratio obtained from Raman analysis.Results showed that increasing the KOH amount led to the achievement of higher values of ID/IG and surface area and less re-stacking of graphene sheets which occurs because of the heat treatment process.The environmental burdens of the production routes for the preparation of EEG and HG were investigated by cradle-to-gate life cycle assessment(LCA).The LCA results of EEG production indicated that electricity with the contributions of 94%,91%,82%,and 75%of the total impact in four environmental categories,including fossil fuel depletion,ozone depletion,global warming,and smog was the main environmental weakness.In the pore generation process,KOH was recognized as the biggest contributor(about 51%to 83%of the total impact)in six impact categories,including ozone depletion,non-carcinogenics,smog,global warming,carcinogenics,and eutrophication which could be attributed to its high consumption amount(21.9 kg).This work offers environmental considerations for the development of sustainable graphene materials.展开更多
As a non-renewable rare industrial gas resource,the decreasing production of helium has stimulated the demand for large-scale storage.Dewar tanks,storage tanks and other liquid helium storage methods are difficult to ...As a non-renewable rare industrial gas resource,the decreasing production of helium has stimulated the demand for large-scale storage.Dewar tanks,storage tanks and other liquid helium storage methods are difficult to meet the needs of largescale and long-term storage.Salt caverns have been widely used in gas energy storage due to their low permeability,which has been proven by decades of stable operation of natural gas storage.However,helium has higher permeability under the same storage conditions,and the feasibility of using rock salt for helium storage has not yet been evaluated by mature theories and standards.In addition,an overlooked fact is that the permeability characteristics of rock salt and micro-permeable layers(MPL)are very different,and MPL can provide leakage channels for high-pressure helium.In this paper,a seepage movement model of small molecule gas in MPL is established.Its calculative accuracy and engineering applicability are verified by the seepage test results.The MPL has crystal structure,which makes the permeability change with different confining pressure and gas injection pressure.The change of permeability is caused by the residual brine in the crystal void.The compaction and the increase of flow velocity of salt rock crystal void increase the viscous resistance and decrease the flow velocity.The permeability of nitrogen and helium in the MPL is different,but the difference decreases at high confining pressure and high injection pressure.In deep salt formations with plateau potential stress,the difference of surrounding rock leakage characteristics between helium and natural gas is smaller,and the expected leakage amount of helium is lower.The paper proposes a numerical calculation model suitable for predicting leaks in salt cavern helium storage facilities with known faults and structural planes,completing the assessment of helium leakage in salt caverns considering the gas physical properties,injection and production conditions,operating pressure,and in-situ stress of surrounding rocks.The above achievements can provide technical references for early-stage leakage prediction and parameter optimization in helium storage salt cavern engineering.展开更多
基金financial supports of National Natural Science Foundation of China (Grant No. 41502296)Youth Innovation Promotion Association, Chinese Academy of Sciences (CAS) (Grant No. 2016296)+1 种基金National Natural Science Foundation of China Innovative Research Team (Grant No. 51621006)Natural Science Foundation for Innovation Group of Hubei Province, China (Grant No. 2016CFA014)
文摘Increasing the allowable gas pressure of underground gas storage(UGS) is one of the most effective methods to increase its working gas capacity. In this context, hydraulic fracturing tests are implemented on the target formation for the UGS construction of Jintan salt caverns, China, in order to obtain the minimum principal in situ stress and the fracture breakdown pressure. Based on the test results, the maximum allowable gas pressure of the Jintan UGS salt cavern is calibrated. To determine the maximum allowable gas pressure, KING-1 and KING-2 caverns are used as examples. A three-dimensional(3D)geomechanical model is established based on the sonar data of the two caverns with respect to the features of the target formation. New criteria for evaluating gas penetration failure and gas seepage are proposed. Results show that the maximum allowable gas pressure of the Jintan UGS salt cavern can be increased from 17 MPa to 18 MPa(i.e. a gradient of about 18 k Pa/m at the casing shoe depth). Based on numerical results, a field test with increasing maximum gas pressure to 18 MPa has been carried out in KING-1 cavern. Microseismic monitoring has been conducted during the test to evaluate the safety of the rock mass around the cavern. Field monitoring data show that KING-1 cavern is safe globally when the maximum gas pressure is increased from 17 MPa to 18 MPa. This shows that the geomechanical model and criteria proposed in this context for evaluating the maximum allowable gas pressure are reliable.
基金funded by the U.S.National Institute for Occupational Safety and Health(NIOSH)under the Contract No.75D30119C06044。
文摘In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for acquiring discontinuity measurements from 3D models,such as point clouds generated using laser scanning or photogrammetry.However,even with numerous automated and semiautomated methods presented in the literature,there is not one single method that can automatically characterize discontinuities accurately in a minimum of time.In this paper,we critically review all the existing methods proposed in the literature for the extraction of discontinuity characteristics such as joint sets and orientations,persistence,joint spacing,roughness and block size using point clouds,digital elevation maps,or meshes.As a result of this review,we identify the strengths and drawbacks of each method used for extracting those characteristics.We found that the approaches based on voxels and region growing are superior in extracting joint planes from 3D point clouds.Normal tensor voting with trace growth algorithm is a robust method for measuring joint trace length from 3D meshes.Spacing is estimated by calculating the perpendicular distance between joint planes.Several independent roughness indices are presented to quantify roughness from 3D surface models,but there is a need to incorporate these indices into automated methodologies.There is a lack of efficient algorithms for direct computation of block size from 3D rock mass surface models.
基金Projects(51621006,51874274)supported by the National Natural Science Foundation of ChinaProject(2018YFC0808401)supported by the National Key Research and Development Program of China
文摘In this paper,a new micro-creep model of salt rock is proposed based on a linear parallel bonded model(LPBM)using the two-dimensional particle flow code(PFC2D).The power function weakening form is assumed to describe the variation of the parallel bonded diameter(PBD)over time.By comparing with the parallel-bonded stress corrosion(PSC)model,a smaller stress fluctuation and smoother creep strain−time curves can be obtained by this power function model at the same stress level.The validity and adaptability of the model to simulate creep deformation of salt rock are verified through comparing the laboratory creep test curves and the Burgers model fitting result.The numerical results reveal that this model can be capable of capturing the creep deformation and damage behavior from the laboratory observations.
文摘A new dynamic model identification method is developed for continuous-time series analysis and forward prediction applications. The quantum of data is defined over moving time intervals in sliding window coordinates for compressing the size of stored data while retaining the resolution of information. Quantum vectors are introduced as the basis of a linear space for defining a Dynamic Quantum Operator (DQO) model of the system defined by its data stream. The transport of the quantum of compressed data is modeled between the time interval bins during the movement of the sliding time window. The DQO model is identified from the samples of the real-time flow of data over the sliding time window. A least-square-fit identification method is used for evaluating the parameters of the quantum operator model, utilizing the repeated use of the sampled data through a number of time steps. The method is tested to analyze, and forward-predict air temperature variations accessed from weather data as well as methane concentration variations obtained from measurements of an operating mine. The results show efficient forward prediction capabilities, surpassing those using neural networks and other methods for the same task.
文摘An analytical model, TA(t), for the observed outside air temperature change, Ta(t), with time is developed using two components: one for the variation caused by the Earth’s movement, plus any other quasi-stationary thermodynamic effects due to industrialization;and one for the random variation caused by stochastic and/or chaotic, local environmental changes. The first component, TR(t), describes a regular trend, expressed by periodic functions of time and constants unchanged with time. The second component, TS, is a random, stochastic variation. For the observed outside air temperature, the analytical model of TA(t)=TR(t) +TS is such as to give a statistically best approximation for the observed time period with = min. Several versions for the TR(t) functions are defined and tested in the study for an example location for 20 years. The best model for TR(t) t is found as a linear function with time plus a variable-coefficient Fourier series with linearly changing amplitude with time. It is found that the final analytical temperature, TA(t), can be used not only to represent the historical daily mean temperature but also to predict the future daily mean temperature at the given location. The upper and lower boundaries give safety limits for the temperature prediction. The stochastic component identified in the model is stable and stationary. The method of model identification for TA(t) can be used for determining input temperature functions for supporting engineering design;or for an unbiased scientific inquiry of temperature change with time in climate studies.
文摘This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(LCA)study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate(HCL)and low-contaminated leachate(LCL).The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity.Also,oxalic acid,Na_(2)CO_(3),and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides(REOs),including solvent extraction(SX)and precipitation steps.The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H_(2)SO_(4)usage,so 468 and 292 kg of carbon dioxide are generated to produce1 t of individual REOs from HCL and LCL routes,respectively.Moreover,the carbon dioxide emitted from the process,including the RE-hydroxide production,SX,and REOs production,is less than 10 t CO_(2).A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process,as the main stage has a higher contribution to the whole process.This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process.
文摘Graphene materials have drawn tremendous attention in recent years.The formation of holes and pores on graphene sheets can provide transfer channels and facilitate the ion/electron transport kinetics.In this study,graphene nanosheets were prepared electrochemically,and then,they were used as the starting material for the preparation of holey graphene(HG)through the KOH activation process.The weight ratio of initial electrochemically exfoliated graphene(EEG)to KOH was optimized according to the morphological features,BET surface area examination,graphene number of layers calculated from XRD patterns,and the ID/IG ratio obtained from Raman analysis.Results showed that increasing the KOH amount led to the achievement of higher values of ID/IG and surface area and less re-stacking of graphene sheets which occurs because of the heat treatment process.The environmental burdens of the production routes for the preparation of EEG and HG were investigated by cradle-to-gate life cycle assessment(LCA).The LCA results of EEG production indicated that electricity with the contributions of 94%,91%,82%,and 75%of the total impact in four environmental categories,including fossil fuel depletion,ozone depletion,global warming,and smog was the main environmental weakness.In the pore generation process,KOH was recognized as the biggest contributor(about 51%to 83%of the total impact)in six impact categories,including ozone depletion,non-carcinogenics,smog,global warming,carcinogenics,and eutrophication which could be attributed to its high consumption amount(21.9 kg).This work offers environmental considerations for the development of sustainable graphene materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.42072307,52404066)the Hubei Province Outstanding Youth Fund(Grant No.2021CFA095)+1 种基金the Natural Science Foundation of Wuhan(Grant Nos.2024040701010062,2024040801020255)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDC10020300)。
文摘As a non-renewable rare industrial gas resource,the decreasing production of helium has stimulated the demand for large-scale storage.Dewar tanks,storage tanks and other liquid helium storage methods are difficult to meet the needs of largescale and long-term storage.Salt caverns have been widely used in gas energy storage due to their low permeability,which has been proven by decades of stable operation of natural gas storage.However,helium has higher permeability under the same storage conditions,and the feasibility of using rock salt for helium storage has not yet been evaluated by mature theories and standards.In addition,an overlooked fact is that the permeability characteristics of rock salt and micro-permeable layers(MPL)are very different,and MPL can provide leakage channels for high-pressure helium.In this paper,a seepage movement model of small molecule gas in MPL is established.Its calculative accuracy and engineering applicability are verified by the seepage test results.The MPL has crystal structure,which makes the permeability change with different confining pressure and gas injection pressure.The change of permeability is caused by the residual brine in the crystal void.The compaction and the increase of flow velocity of salt rock crystal void increase the viscous resistance and decrease the flow velocity.The permeability of nitrogen and helium in the MPL is different,but the difference decreases at high confining pressure and high injection pressure.In deep salt formations with plateau potential stress,the difference of surrounding rock leakage characteristics between helium and natural gas is smaller,and the expected leakage amount of helium is lower.The paper proposes a numerical calculation model suitable for predicting leaks in salt cavern helium storage facilities with known faults and structural planes,completing the assessment of helium leakage in salt caverns considering the gas physical properties,injection and production conditions,operating pressure,and in-situ stress of surrounding rocks.The above achievements can provide technical references for early-stage leakage prediction and parameter optimization in helium storage salt cavern engineering.
