Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fractu...Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fracturing and leakage.In this study,we present an integrated experimental and numerical investigation to quantify the effects of particle migration on formation pressure and the spatial diffusion of injected water.Dynamic plugging experiments were performed to systematically examine the influence of injection rate and injection volume on core permeability.Results demonstrate that higher injection rates substantially reduce permeability,and the derived relationship between permeability and injection volume enables dynamic assessment of permeability evolution during reinjection.Complementary numerical simulations explored the impacts of injection length,particle concentration,and injection rate on formation pressure and diffusion behavior.Findings indicate that extending the injection section promotes pressure distribution and enlarges the diffusion area,whereas elevated particle concentrations and injection rates accelerate formation plugging,causing rapid pressure rise and constrained diffusion.展开更多
Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behavi...Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.展开更多
The shear-induced migration of neutrally-buoyant non-colloidal circular particles in a two-dimensional circular Couette flow is investigated numerically with a distributed Lagrange multiplier based fictitious domain m...The shear-induced migration of neutrally-buoyant non-colloidal circular particles in a two-dimensional circular Couette flow is investigated numerically with a distributed Lagrange multiplier based fictitious domain method.The effects of inertia and volume fraction on the particle migration are examined.The results indicate that inertia has a negative effect on the particle migration.In consistence with the experimental observations,the rapid migration of particles near the inner cylinder at the early stage is observed in the simulation,which is believed to be related to the chain-like clustering of particles.The migration of circular particles in a plane Poiseuille flow is also examined in order to further confirm the effect of such clustering on the particle migration at early stage.There is tendency for the particles in the vicinity of outer cylinder in the Couette device to pack into concentric rings at late stage in case of high particle concentration.展开更多
Particle redistribution occurred with the flow of pool fluid in laser welding aluminum composites. In order to investigate particle migration behavior, a numerical model was established on laser welding of ZL101-TiB2 ...Particle redistribution occurred with the flow of pool fluid in laser welding aluminum composites. In order to investigate particle migration behavior, a numerical model was established on laser welding of ZL101-TiB2 composite. TiB2 migration coupling with fluid was realized. The volume-of-fluid （VOF） method was employed to track free fluid surfaces. The travel heat source was realized utilizing the workpiece mo- tion in place of heat source motion, which made the heat load stable. Melting and evaporation enthalpy, recoil force, surface tension and buoyancy were considered in this model. Through the calculation it showed that the simulated weld cross section shape and particle distribution were in good agreement with experimental results.展开更多
We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidificat...We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys.Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed.They include introduction,high-gradient magnetic field effects,migration behavior of solute and particles in high-gradient magnetic fields,microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles,and properties of materials modified by high-gradient magnetic field-tailored microstructure.Selected examples of binary and multiphase alloy systems are presented and examined,with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution.Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.展开更多
Currently,Robinia pseudoacacia L.is distributed extensively across the Chinese Loess Plateau.Root exudates released by Robinia pseudoacacia L.are one of the mechanisms through which Robinia pseudoacacia L.affects soil...Currently,Robinia pseudoacacia L.is distributed extensively across the Chinese Loess Plateau.Root exudates released by Robinia pseudoacacia L.are one of the mechanisms through which Robinia pseudoacacia L.affects soil properties.However,how root exudates influencethe hydraulic properties of soil remains unclear,especially for fine-grained soils.This knowledge gap impedes a comprehensive understanding of the function of vegetation in wastewater treatment,ecological restoration,and seepage analysis.To investigate the effect and underlying mechanisms of the root exudates of Robinia pseudoacacia L.on the saturated hydraulic conductivity of loess(a fine-grainedsoil),the saturated hydraulic conductivity,bound water content,grain size distribution,and microstructure characteristics of loess treated with root exudates at varying concentrations were determined in this study through a series of tests.The results show that the mean saturated hydraulic conductivities of the loess specimens with root exudates are all lower than those without root exudates.This phenomenon can be attributed primarily to the capacity of root exudates to directly and indirectly increase the bound water content,leading to a decrease in the effective seepage channels of the loess.For loess with/without root exudates,the variation of saturated hydraulic conductivity over time can be divided into three stages:an initial constant stage,a rapid reduction stage,and a re-stabilization stage.This is primarily attributed to the migration of particles within a specifiedsize range(7-30μm)and pore-clogging in the specimens during the seepage process.A schematic diagram is proposed for the structural evolution of fine-grained soil with or without root exudates during long-term seepage.展开更多
Karst collapse columns typically appear unpredictably and without a uniform spatial arrangement,posing challenges for mining operations and water inrush risk assessment.As major structural pathways for mine water inru...Karst collapse columns typically appear unpredictably and without a uniform spatial arrangement,posing challenges for mining operations and water inrush risk assessment.As major structural pathways for mine water inrush,they are responsible for some of the most frequent and severe water-related disasters in coal mining.Understanding the mechanisms of water inrush in these collapse columns is therefore essential for effective disaster prevention and control,making it a key research priority.Additionally,investigating the developmental characteristics of collapse columns is crucial for analyzing seepage instability mechanisms.In such a context,this paper provides a comprehensive review of four critical aspects:(1)The development characteristics and hydrogeological properties of collapse columns;(2)Fluid-solid coupling mechanisms under mining-induced stress;(3)Non-Darcy seepage behavior in fractured rock masses;(4)Flow regime transitions and mass variation effects.Key findings highlight the role of flow-solid coupling in governing the seepage mechanisms of fractured rock masses within karst collapse columns.By synthesizing numerous studies on flow pattern transitions,this paper outlines the complete seepage process-from groundwater movement within the aquifer to its migration through the collapse column and eventual inflow into mine roadways or working faces-along with the associated transformations in flow patterns.Furthermore,the seepage characteristics and water inrush behaviors influenced by particle migration are examined through both experimental and numerical simulation approaches.展开更多
The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine parti...The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particleaccumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.展开更多
The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new dr...The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.展开更多
Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was est...Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was established to analyze the dynamic responses of a ballastless track,and results showed that the concrete base and roadbed were detached because of the whipping effect arising from the rainwater intrusion channel.An in-situ soil core test showed that the intruded rainwater accumulated in roadbed to form standing water and saturated the roadbed.The flapping action of the concrete base caused by the whipping effect led to mud formation mixed with fine particles and rainwater,which migrated upward under the pore-water pressure(PWP)gradient.Mud pumping resulted from continuous particle migration in the saturated roadbed under moving train loads:under normal roadbed condition,coarse and fine particles were uniformly distributed in the roadbed;in early period of mud pumping,fine particles migrated downward to bottom of the roadbed because of the rainwater infiltration flow;in middle stage of mud pumping,fine particles migrated upward and gathered at the roadbed surface under PWP gradient;in later period of mud pumping,fine particles were entrained and removed with the dissipation of excess PWP.Moreover,a full-scale physical model was established to reproduce mud pumping,and polyurethane injection remediation against mud pumping was validated on this physical model.The remediation method was applied to an in-situ mud pumping.The deviation of the vertical track profile reduced remarkably and remained at a low level within half a year,showing a good long-term service performance of the polyurethane remediated roadbed.展开更多
In this paper,the Lower Silurian Longmaxi shale samples and the backflow fracturing fluid in the Changning Block of the Sichuan Basin were selected to investigate the damage mechanism of retained fracturing fluid to f...In this paper,the Lower Silurian Longmaxi shale samples and the backflow fracturing fluid in the Changning Block of the Sichuan Basin were selected to investigate the damage mechanism of retained fracturing fluid to fractures in shale gas reservoirs.Thus,experiments were conducted on fracturing fluid backflow and gas-driving fracturing fluids.The changes of liquid permeability of shale samples,solid particle size distribution and turbidity of the backflow fracturing fluid were monitored.The gas permeability before and after fracturing fluid gas drive was compared,and the damage degree and mechanism of the backflow fracturing fluid to the fractures in shale samples were analyzed.And the following research results were obtained.First,the damage rate of shale permeability after the fracturing fluid backflow is between 53.1%and 97.6%,and the range of the solid particle size of the flowback fluid is significantly reduced.The main reservoir damage modes include phase trapping damage caused by liquid phase retention,blockage caused by the solid phase residue,particle migration induced by gas-carrying liquid and salt precipitation.Second,in the stage of gas phase flow,the damage rate of permeability drops to 23.1-80.2%,and the damage caused by liquid phase retention is relieved,but the damage caused by the blockage of solid phase residue and the salt precipitation of flowback on the facture surface is inevitable.Third,based on the damage mechanism of fracturing fluid backflow in shale gas wells to fractures,considering the treatment difficulty of the flowback and its damage to reservoir fractures,it is recommended to give a full play to the fracturing capacity of fracturing fluid and optimize the properties and dosages of fracturing fluid so as to reduce the flowback of fracturing fluid as much as possible.展开更多
At present, there are many problems in the field water injection work of Fan 107 block in Daluhu oilfield, such as high water injection pressure, difficulty in taking effect after water injection and uneven effect. Ba...At present, there are many problems in the field water injection work of Fan 107 block in Daluhu oilfield, such as high water injection pressure, difficulty in taking effect after water injection and uneven effect. Based on the experimental analysis of reservoir physical properties by using reservoir cores and on-site source water, this paper focuses on the adaptability of source water and reservoir through core displacement test, i.e. the impact of long-term scouring on reservoir rocks and the comprehensive damage degree and damage rule of mechanical impurity particle blockage. The test results show that the main factors of reservoir damage caused by injected source water are water sensitivity damage caused by low salinity source water and particle migration damage of the reservoir itself caused by long-term scouring, while the suspended solid particles in on-site source water are not the main reservoir damage factors. Aiming at the main damage factors, clay stabilizer and clay anti-swelling agent are added to the source water to reduce the reservoir damage. This research work provides experimental basis for solving the compatibility problem of block injection water quality and improving the block injection effect.展开更多
基金supported by the National Natural Science Foundation of China(No.52204026).
文摘Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fracturing and leakage.In this study,we present an integrated experimental and numerical investigation to quantify the effects of particle migration on formation pressure and the spatial diffusion of injected water.Dynamic plugging experiments were performed to systematically examine the influence of injection rate and injection volume on core permeability.Results demonstrate that higher injection rates substantially reduce permeability,and the derived relationship between permeability and injection volume enables dynamic assessment of permeability evolution during reinjection.Complementary numerical simulations explored the impacts of injection length,particle concentration,and injection rate on formation pressure and diffusion behavior.Findings indicate that extending the injection section promotes pressure distribution and enlarges the diffusion area,whereas elevated particle concentrations and injection rates accelerate formation plugging,causing rapid pressure rise and constrained diffusion.
基金supported by the Laoshan Laboratory(No.LSKJ LSKJ202203506)the Taishan Scholars Program,and the National Natural Science Foundation of China(Grant No.41976074).
文摘Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.
基金Supported by the National Natural Science Foundation of China （No. 10472104）.
文摘The shear-induced migration of neutrally-buoyant non-colloidal circular particles in a two-dimensional circular Couette flow is investigated numerically with a distributed Lagrange multiplier based fictitious domain method.The effects of inertia and volume fraction on the particle migration are examined.The results indicate that inertia has a negative effect on the particle migration.In consistence with the experimental observations,the rapid migration of particles near the inner cylinder at the early stage is observed in the simulation,which is believed to be related to the chain-like clustering of particles.The migration of circular particles in a plane Poiseuille flow is also examined in order to further confirm the effect of such clustering on the particle migration at early stage.There is tendency for the particles in the vicinity of outer cylinder in the Couette device to pack into concentric rings at late stage in case of high particle concentration.
基金supported by the Shanghai Natural Science Foundation of China(No.11ZR1417500)
文摘Particle redistribution occurred with the flow of pool fluid in laser welding aluminum composites. In order to investigate particle migration behavior, a numerical model was established on laser welding of ZL101-TiB2 composite. TiB2 migration coupling with fluid was realized. The volume-of-fluid （VOF） method was employed to track free fluid surfaces. The travel heat source was realized utilizing the workpiece mo- tion in place of heat source motion, which made the heat load stable. Melting and evaporation enthalpy, recoil force, surface tension and buoyancy were considered in this model. Through the calculation it showed that the simulated weld cross section shape and particle distribution were in good agreement with experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51425401,51690161,51574073,and 51774086)Fundamental Research Funds for the Central Universities,China(Grant Nos.N170902002 and N170908001)Liaoning Innovative Research Team in University,China(Grant No.LT2017011)
文摘We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys.Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed.They include introduction,high-gradient magnetic field effects,migration behavior of solute and particles in high-gradient magnetic fields,microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles,and properties of materials modified by high-gradient magnetic field-tailored microstructure.Selected examples of binary and multiphase alloy systems are presented and examined,with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution.Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.
基金financial support from the National Natural Science Foundation of China(Grant Nos.42007251 and 42027806)the Doctoral Dissertation Cultivation Project of Northwest University(Grant No.YB2024016).
文摘Currently,Robinia pseudoacacia L.is distributed extensively across the Chinese Loess Plateau.Root exudates released by Robinia pseudoacacia L.are one of the mechanisms through which Robinia pseudoacacia L.affects soil properties.However,how root exudates influencethe hydraulic properties of soil remains unclear,especially for fine-grained soils.This knowledge gap impedes a comprehensive understanding of the function of vegetation in wastewater treatment,ecological restoration,and seepage analysis.To investigate the effect and underlying mechanisms of the root exudates of Robinia pseudoacacia L.on the saturated hydraulic conductivity of loess(a fine-grainedsoil),the saturated hydraulic conductivity,bound water content,grain size distribution,and microstructure characteristics of loess treated with root exudates at varying concentrations were determined in this study through a series of tests.The results show that the mean saturated hydraulic conductivities of the loess specimens with root exudates are all lower than those without root exudates.This phenomenon can be attributed primarily to the capacity of root exudates to directly and indirectly increase the bound water content,leading to a decrease in the effective seepage channels of the loess.For loess with/without root exudates,the variation of saturated hydraulic conductivity over time can be divided into three stages:an initial constant stage,a rapid reduction stage,and a re-stabilization stage.This is primarily attributed to the migration of particles within a specifiedsize range(7-30μm)and pore-clogging in the specimens during the seepage process.A schematic diagram is proposed for the structural evolution of fine-grained soil with or without root exudates during long-term seepage.
基金supported by the Natural Science Foundation of Henan Province(242300421246,222300420007,232300421134)the National Natural Science Foundation of China(52004082,52174073,52274079,42402255)+4 种基金the Science and Technology Project of Henan Province(232102321098)Zhongyuan Science and Technology Innovation Leading Talent Program(244200510005)the Program for Science&Technology Innovation Talents in Universities of Henan Province(24HASTIT021)the Program for the Scientific and Technological Innovation Team in Universities of Henan Province(23IRTSTHN005)the National Postdoctoral Researchers Program Foundation of China(GZC20230709)。
文摘Karst collapse columns typically appear unpredictably and without a uniform spatial arrangement,posing challenges for mining operations and water inrush risk assessment.As major structural pathways for mine water inrush,they are responsible for some of the most frequent and severe water-related disasters in coal mining.Understanding the mechanisms of water inrush in these collapse columns is therefore essential for effective disaster prevention and control,making it a key research priority.Additionally,investigating the developmental characteristics of collapse columns is crucial for analyzing seepage instability mechanisms.In such a context,this paper provides a comprehensive review of four critical aspects:(1)The development characteristics and hydrogeological properties of collapse columns;(2)Fluid-solid coupling mechanisms under mining-induced stress;(3)Non-Darcy seepage behavior in fractured rock masses;(4)Flow regime transitions and mass variation effects.Key findings highlight the role of flow-solid coupling in governing the seepage mechanisms of fractured rock masses within karst collapse columns.By synthesizing numerous studies on flow pattern transitions,this paper outlines the complete seepage process-from groundwater movement within the aquifer to its migration through the collapse column and eventual inflow into mine roadways or working faces-along with the associated transformations in flow patterns.Furthermore,the seepage characteristics and water inrush behaviors influenced by particle migration are examined through both experimental and numerical simulation approaches.
基金supported by the key international collaborative project of Natural Science Foundation of China(No.41520104002)
文摘The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particleaccumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.
基金supported by the Basic Research Program Project of Qinghai Province(No.2020-ZJ-758)the Special Fund on the Exploration of Clean Energy and Mineral Products in Qinghai Province(20181317146sh 007)partially financed by the General Project of Shandong Natural Science Foundation(ZR2020ME090)。
文摘The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.
基金This article was supported by the National Natural Science Foundation of China(No.52125803,No.51988101,and No.52008369)the National Key Research and Development Program(No.2018YFE0207100).
文摘Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was established to analyze the dynamic responses of a ballastless track,and results showed that the concrete base and roadbed were detached because of the whipping effect arising from the rainwater intrusion channel.An in-situ soil core test showed that the intruded rainwater accumulated in roadbed to form standing water and saturated the roadbed.The flapping action of the concrete base caused by the whipping effect led to mud formation mixed with fine particles and rainwater,which migrated upward under the pore-water pressure(PWP)gradient.Mud pumping resulted from continuous particle migration in the saturated roadbed under moving train loads:under normal roadbed condition,coarse and fine particles were uniformly distributed in the roadbed;in early period of mud pumping,fine particles migrated downward to bottom of the roadbed because of the rainwater infiltration flow;in middle stage of mud pumping,fine particles migrated upward and gathered at the roadbed surface under PWP gradient;in later period of mud pumping,fine particles were entrained and removed with the dissipation of excess PWP.Moreover,a full-scale physical model was established to reproduce mud pumping,and polyurethane injection remediation against mud pumping was validated on this physical model.The remediation method was applied to an in-situ mud pumping.The deviation of the vertical track profile reduced remarkably and remained at a low level within half a year,showing a good long-term service performance of the polyurethane remediated roadbed.
基金supported by General Program of National Natural Science Foundation of China"Study on the gas transmission mechanism for permeability improvement and acceleration through oxidation-assisted cracking in organic matter-enriched shale"(No.:51674209)Major Breeding Project of Sichuan Provincial Colleges,Universities for Conversion of Scientific&Technological Achievements"Method of improving gas recovery of organic matter-enriched shale gas reservoirs"(No.:17CZ0040)2017 Science&Technology Project of PetroChina Southwest Oil&Gasfield Company"Study on the interaction mechanism of shale and fracturing fluids and flowback rules in the Changning Block"(No.20170302-03).
文摘In this paper,the Lower Silurian Longmaxi shale samples and the backflow fracturing fluid in the Changning Block of the Sichuan Basin were selected to investigate the damage mechanism of retained fracturing fluid to fractures in shale gas reservoirs.Thus,experiments were conducted on fracturing fluid backflow and gas-driving fracturing fluids.The changes of liquid permeability of shale samples,solid particle size distribution and turbidity of the backflow fracturing fluid were monitored.The gas permeability before and after fracturing fluid gas drive was compared,and the damage degree and mechanism of the backflow fracturing fluid to the fractures in shale samples were analyzed.And the following research results were obtained.First,the damage rate of shale permeability after the fracturing fluid backflow is between 53.1%and 97.6%,and the range of the solid particle size of the flowback fluid is significantly reduced.The main reservoir damage modes include phase trapping damage caused by liquid phase retention,blockage caused by the solid phase residue,particle migration induced by gas-carrying liquid and salt precipitation.Second,in the stage of gas phase flow,the damage rate of permeability drops to 23.1-80.2%,and the damage caused by liquid phase retention is relieved,but the damage caused by the blockage of solid phase residue and the salt precipitation of flowback on the facture surface is inevitable.Third,based on the damage mechanism of fracturing fluid backflow in shale gas wells to fractures,considering the treatment difficulty of the flowback and its damage to reservoir fractures,it is recommended to give a full play to the fracturing capacity of fracturing fluid and optimize the properties and dosages of fracturing fluid so as to reduce the flowback of fracturing fluid as much as possible.
文摘At present, there are many problems in the field water injection work of Fan 107 block in Daluhu oilfield, such as high water injection pressure, difficulty in taking effect after water injection and uneven effect. Based on the experimental analysis of reservoir physical properties by using reservoir cores and on-site source water, this paper focuses on the adaptability of source water and reservoir through core displacement test, i.e. the impact of long-term scouring on reservoir rocks and the comprehensive damage degree and damage rule of mechanical impurity particle blockage. The test results show that the main factors of reservoir damage caused by injected source water are water sensitivity damage caused by low salinity source water and particle migration damage of the reservoir itself caused by long-term scouring, while the suspended solid particles in on-site source water are not the main reservoir damage factors. Aiming at the main damage factors, clay stabilizer and clay anti-swelling agent are added to the source water to reduce the reservoir damage. This research work provides experimental basis for solving the compatibility problem of block injection water quality and improving the block injection effect.
