According to the physical and chemical characteristics of superfine powder extinguishing agent,three test methods are selected to measure the flow ability.By studying and comparing various test methods,apparatus and c...According to the physical and chemical characteristics of superfine powder extinguishing agent,three test methods are selected to measure the flow ability.By studying and comparing various test methods,apparatus and conditions,the optimum method and conditions to test flow property of superfine powder extinguishing agent are confirmed.展开更多
Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale m...Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.展开更多
The accurate parameters measurement of the flow field between the stages for axial compressors is a significant demand.This paper proposes an axial compressor inter-stage flow field high-precision test system,which ma...The accurate parameters measurement of the flow field between the stages for axial compressors is a significant demand.This paper proposes an axial compressor inter-stage flow field high-precision test system,which mainly consists of a probe motion scanning mechanism,fully automated test control software,and data processing methods.Iterative correction is applied to the original readings obtained from the scanning tests to enhance testing accuracy.Using this test system,detailed tests are conducted on a 1.5-stage subsonic axial compressor under different operating conditions.The test results effectively captured the impact of surface roughness and tip clearance variations on compressor performance.The distribution characteristics of parameters measured in inter-stage sections can characterize the effects of blade wake area and changes in aerodynamic performance at different blade heights.The developed test system can be extended to multi-stage compressors.展开更多
In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility...In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.展开更多
After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coeffici...After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport.展开更多
Based on the flow mechanism of hydraulic fractured wells, through integrating linear-flow model and effective well-radius model, a new model of well test analysis for wells with vertical fracture was established. In t...Based on the flow mechanism of hydraulic fractured wells, through integrating linear-flow model and effective well-radius model, a new model of well test analysis for wells with vertical fracture was established. In the model, wellbore storage, the damage in the wall of fracture and all kinds of boundary conditions are considered. The model is concise in form, has intact curves and computes fast, which may meet the demand of real-time computation and fast responded well test interpretation. A new method to determine effective well radius was presented, and the correlation between effective well radius and the fracture length, fracture conductivity, skin factor of fracture was given. Matching flow rate or pressure tested, the optimization model that identified formation and fracture parameters was set up. The automatic matching method was presented by synthetically using step by step linear least square method and sequential quadratic programming. At last, the application was also discussed. Application shows that all of these results can analyze and evaluate the fracturing treatment quality scientifically and rationally, instruct and modify the design of fracturing and improve fracturing design level.展开更多
The prevention and control of natural gas hydrate(hereinafter,“hydrate”for short)blockage during deepwater gas well production tests is very important in ensuring the test safety.In this paper,the distribution of we...The prevention and control of natural gas hydrate(hereinafter,“hydrate”for short)blockage during deepwater gas well production tests is very important in ensuring the test safety.In this paper,the distribution of wellbore temperature and pressure field under different test conditions was analyzed,and the changes of hydrate deposition and blockage degree in the pipe string in the whole process of test under different test systems were evaluated using the hydrate generationedepositionedecomposition calculation method.On this basis,a deepwater gas well production test method based on hydrate prevention and control was proposed.And the following research results were obtained.First,in the process of deepwater gas well tests,the vaporeliquid phase of annular-mist flow pattern with the greatest risk of hydrate blockage is often formed in the wellbore.Therefore,it is more reasonable to take measures to prevent hydrate blockage in the process of tests than to prevent the formation of hydrate.Second,when the conventional four-point test method is used,it is required to set low gas production measurement points with lower flowing temperature.In the wellbore with high temperature and low temperature,however,hydrate tends to form and deposit easily,and a long period of test will increase the risk of test string blockage.Third,the mixed-sequence test system suitable for deepwater gas well tests can change wellbore temperature by adjusting the sequence of measuring points without changing the production rate and duration,so as to decompose hydrate sediment layers and reduce the maximum blockage degree of test string in the process of tests.Fourth,a three-point or two-point test method is recommended for deepwater gas wells without sand production,stress sensitivity,retrograde condensation and water production.Superior to the conventional four-point test method,three-point and two-point test methods can effectively reduce the risk of hydrate deposition and blockage in the test string,and it can shorten the testing time and reduce the test cost on the premise of ensuring the accuracy of the productivity equation.In conclusion,the research results are of help to the field test construction of deepwater gas wells.展开更多
Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention...Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.展开更多
In order to advance the understanding of the impact dynamics of granular flow in complex geological settings,this paper studied the impact dynamics of granular flow on rigid barriers with a number of Material Point Me...In order to advance the understanding of the impact dynamics of granular flow in complex geological settings,this paper studied the impact dynamics of granular flow on rigid barriers with a number of Material Point Method(MPM)numerical tests.The impact behavior of granular flow on a rigid barrier was characterized by the initial dynamic impact stage,dynamic surge impact stage,compression impact stage and static stage of granular flow,where the impact force of granular flow was comprised of the dynamic and static forces of granular flow.The impact behavior of granular flow on a rigid barrier was characterized by the states of the fast or slow impact behavior of granular flow.The angle of slope and aspect ratio of granular soil greatly affected the impact behavior of granular flow on a column rigid barrier,where a power model was proposed to quantify the residual(Fnr)-over-maximum(Fnmax)normal impact force ratio of granular flow Fnr⁄Fnmax incorporating the effects of the angle of slope and aspect ratio of granular soil.With the increase of the column rigid barrier up to the semi-infinite column rigid barrier,the impact dynamics of granular flow gradually increased up to a maximum by progressively transforming the overflow into the dynamic surge impact of the incoming flow on the rigid barrier to capture more granular soil of granular flow against the rigid barrier.Presence of water in granular flow,i.e.,a mixture of solid and liquid in granular flow,yielded a dynamic coupling contribution of the solid and liquid,being accompanied by the whole dynamic process of granular flow,on the impact behavior of granular flow on a rigid barrier,where the liquid-phase material of granular flow,i.e.,the water,was predominant to contribute on the normal impact force of granular flow in comparison with the solid-phase material of granular flow.In addition,other factors,e.g.,the shape of rigid barrier(i.e.,the column barrier,arch barrier and circle barrier),and the gravity(i.e.,in the gravitational environment of the Moon,Earth and Mars),greatly affected the impact behavior of granular flow on a rigid barrier as well.展开更多
When using the plug pulse decay method to measure shale permeability,a comprehensive analysis of various factors influencing the measurement and analysis precision is conducive to improving the accuracy of the test re...When using the plug pulse decay method to measure shale permeability,a comprehensive analysis of various factors influencing the measurement and analysis precision is conducive to improving the accuracy of the test result.A great number of nano-scale pores are developed in shale,so the lower the test pressure is,the more easily the non-Darcy flow tends to emerge.In order to ensure the gas is in the form of Darcy flow in the process of measurement,we put forward the lower pressure limit of Darcy flow in pores according to the definition of Knudsen number.Then,the gas desorption-flow coupling model for the gas flow process during the plug pulse decay measurement was established by considering the effects of gas on the adsorption in organic pores.After the partial differential equation set was solved and derived,the corresponding permeability calculation method was proposed.Finally,after the plug pulse decay measurement,the supporting nitrogen isothermal adsorption test and methane isothermal adsorption test were conducted on shale samples.And the following research results were obtained.First,during the plug pulse decay measurement,the flow of gas in rock samples is one-dimensional linear,so when establishing the flow equation,the gas pseudopressure can be replaced with the gas pressure to simplify the calculation.Second,the adsorption of nitrogen in shale is much less than that of methane in shale,so the influence of nitrogen desorption on the flow is negligible when the pressure difference(i.e.<5%)of upstream and downstream changes within 5%of the initial pore pressure.In conclusion,the available industrial standards don't take into consideration the influence of gas adsorption,but the shale permeability measurement can still satisfy the accuracy requirement.展开更多
利用计算机视觉对桥梁结构进行位移测量,常见的方法有特征点算法和光流法。为解决光照变化对光流法的精度影响,以及特征点法难以对目标进行实时跟踪等问题,以定向FAST与旋转BRIEF(oriented FAST and rotated BRIEF,ORB)特征点算法提取...利用计算机视觉对桥梁结构进行位移测量,常见的方法有特征点算法和光流法。为解决光照变化对光流法的精度影响,以及特征点法难以对目标进行实时跟踪等问题,以定向FAST与旋转BRIEF(oriented FAST and rotated BRIEF,ORB)特征点算法提取目标特征点,并结合LK(Lucas-Kanade)光流法进行跟踪。通过两种算法的互补融合,并设定周期性更新策略,有效减少误差积累。在室内进行了钢板梁模型激振试验,探讨光照变化对算法性能的影响。将算法得到的位移数据与激光位移计测量结果进行对比,以验证其准确性。此外,还将该算法与FAST-LK、SIFT-LK、Shi-Tomasi-LK、siamRPN++等算法进行比对分析。结果表明:该算法得到的位移曲线拟合程度在95%以上,误差控制在5%之内,验证了其可行性,同时,试验表明该方法对光照变化具有一定的鲁棒性,并能达到实时性的要求。展开更多
微结构探测器是目前国际上气体探测器研究的热点,但普通微结构探测器的性能无法满足核保障等研究领域对能量分辨的要求。为此团队自主研制了一种高能量分辨MicroMegas探测器。通过建立测试系统对探测器进行测试,发现其性能不仅取决于探...微结构探测器是目前国际上气体探测器研究的热点,但普通微结构探测器的性能无法满足核保障等研究领域对能量分辨的要求。为此团队自主研制了一种高能量分辨MicroMegas探测器。通过建立测试系统对探测器进行测试,发现其性能不仅取决于探测器本身的制作工艺,还与系统的使用及测试方法紧密相关。为充分发挥探测器性能,需要对气体探测器性能影响的各方面因素进行测试与分析,建立数据库,优化测试系统和实验条件。在上述研究基础上,利用^(55)Fe放射源在Ar+5%iC_4H_(10)的气体下对原子能院制作的MicroMegas进行能量分辨测试,在5.9 ke V能量下获得能量分辨的平均值为11.7%,与目前国际上微结构探测器的最好水平持平。通过优化测试系统和实验条件,能够获得更加稳定的探测器性能,更容易在核保障、核物理与辐射探测领域推广。展开更多
文摘According to the physical and chemical characteristics of superfine powder extinguishing agent,three test methods are selected to measure the flow ability.By studying and comparing various test methods,apparatus and conditions,the optimum method and conditions to test flow property of superfine powder extinguishing agent are confirmed.
基金Project(51108190) supported by the National Natural Science Foundation of ChinaProject(2012ZC27) supported by the Independence Research Subject from State Key Laboratory of Subtropical Building Science,ChinaProject(GTCC 2008-253) supported by the Research Subject from Guangzhou City,China
文摘Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.
基金National Science and Technology Major Project of China No.2017-V-0012-0064。
文摘The accurate parameters measurement of the flow field between the stages for axial compressors is a significant demand.This paper proposes an axial compressor inter-stage flow field high-precision test system,which mainly consists of a probe motion scanning mechanism,fully automated test control software,and data processing methods.Iterative correction is applied to the original readings obtained from the scanning tests to enhance testing accuracy.Using this test system,detailed tests are conducted on a 1.5-stage subsonic axial compressor under different operating conditions.The test results effectively captured the impact of surface roughness and tip clearance variations on compressor performance.The distribution characteristics of parameters measured in inter-stage sections can characterize the effects of blade wake area and changes in aerodynamic performance at different blade heights.The developed test system can be extended to multi-stage compressors.
基金This work was supported by the National Natural Science Foundation of China(Grant no.U22A20603)Sichuan Science and Technology Program-China(Grant No.2023ZYD0149)CAS"Light of West China"Program-China(Grant No.Fangwei Yu).In addition,a special acknowledgement should be expressed to a famous Chinese television drama:My Chief and My Regiment that accompanied me(Dr.Fangwei Yu)through the loneliness time of completing this study.
文摘In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.
基金Supported by Major State Basic Research Development Program of China("973" Program,No.2010CB732106)
文摘After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport.
基金theNaturalGasExploitationKeyLabofSichuanProvince (No .0 1 6)
文摘Based on the flow mechanism of hydraulic fractured wells, through integrating linear-flow model and effective well-radius model, a new model of well test analysis for wells with vertical fracture was established. In the model, wellbore storage, the damage in the wall of fracture and all kinds of boundary conditions are considered. The model is concise in form, has intact curves and computes fast, which may meet the demand of real-time computation and fast responded well test interpretation. A new method to determine effective well radius was presented, and the correlation between effective well radius and the fracture length, fracture conductivity, skin factor of fracture was given. Matching flow rate or pressure tested, the optimization model that identified formation and fracture parameters was set up. The automatic matching method was presented by synthetically using step by step linear least square method and sequential quadratic programming. At last, the application was also discussed. Application shows that all of these results can analyze and evaluate the fracturing treatment quality scientifically and rationally, instruct and modify the design of fracturing and improve fracturing design level.
基金supported by the National Program on Key Basic Research Project(973 Program)“Deep-water oil and gas well completion and production tests optimization”(No.:2015CB251205).
文摘The prevention and control of natural gas hydrate(hereinafter,“hydrate”for short)blockage during deepwater gas well production tests is very important in ensuring the test safety.In this paper,the distribution of wellbore temperature and pressure field under different test conditions was analyzed,and the changes of hydrate deposition and blockage degree in the pipe string in the whole process of test under different test systems were evaluated using the hydrate generationedepositionedecomposition calculation method.On this basis,a deepwater gas well production test method based on hydrate prevention and control was proposed.And the following research results were obtained.First,in the process of deepwater gas well tests,the vaporeliquid phase of annular-mist flow pattern with the greatest risk of hydrate blockage is often formed in the wellbore.Therefore,it is more reasonable to take measures to prevent hydrate blockage in the process of tests than to prevent the formation of hydrate.Second,when the conventional four-point test method is used,it is required to set low gas production measurement points with lower flowing temperature.In the wellbore with high temperature and low temperature,however,hydrate tends to form and deposit easily,and a long period of test will increase the risk of test string blockage.Third,the mixed-sequence test system suitable for deepwater gas well tests can change wellbore temperature by adjusting the sequence of measuring points without changing the production rate and duration,so as to decompose hydrate sediment layers and reduce the maximum blockage degree of test string in the process of tests.Fourth,a three-point or two-point test method is recommended for deepwater gas wells without sand production,stress sensitivity,retrograde condensation and water production.Superior to the conventional four-point test method,three-point and two-point test methods can effectively reduce the risk of hydrate deposition and blockage in the test string,and it can shorten the testing time and reduce the test cost on the premise of ensuring the accuracy of the productivity equation.In conclusion,the research results are of help to the field test construction of deepwater gas wells.
基金Project supported by the National Program on Key Basic Research Project(973 Program)"Basic research on safe and efficient drilling and completion of marine deepwater oil and gas wells"(No.:2015CB251204)the National Science Foundation for Distinguished Young Scholars“Theory and application of multiphase flow of oil and gas wells”(No.:51622405).
文摘Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.
基金supported by the Sichuan Science and Technology Program - China (Grant no. 2023ZYD0149)National Natural Science Foundation of China (Grant no. U22A20603)CAS "Light of West China" Program - China (Grant No. Fangwei Yu)
文摘In order to advance the understanding of the impact dynamics of granular flow in complex geological settings,this paper studied the impact dynamics of granular flow on rigid barriers with a number of Material Point Method(MPM)numerical tests.The impact behavior of granular flow on a rigid barrier was characterized by the initial dynamic impact stage,dynamic surge impact stage,compression impact stage and static stage of granular flow,where the impact force of granular flow was comprised of the dynamic and static forces of granular flow.The impact behavior of granular flow on a rigid barrier was characterized by the states of the fast or slow impact behavior of granular flow.The angle of slope and aspect ratio of granular soil greatly affected the impact behavior of granular flow on a column rigid barrier,where a power model was proposed to quantify the residual(Fnr)-over-maximum(Fnmax)normal impact force ratio of granular flow Fnr⁄Fnmax incorporating the effects of the angle of slope and aspect ratio of granular soil.With the increase of the column rigid barrier up to the semi-infinite column rigid barrier,the impact dynamics of granular flow gradually increased up to a maximum by progressively transforming the overflow into the dynamic surge impact of the incoming flow on the rigid barrier to capture more granular soil of granular flow against the rigid barrier.Presence of water in granular flow,i.e.,a mixture of solid and liquid in granular flow,yielded a dynamic coupling contribution of the solid and liquid,being accompanied by the whole dynamic process of granular flow,on the impact behavior of granular flow on a rigid barrier,where the liquid-phase material of granular flow,i.e.,the water,was predominant to contribute on the normal impact force of granular flow in comparison with the solid-phase material of granular flow.In addition,other factors,e.g.,the shape of rigid barrier(i.e.,the column barrier,arch barrier and circle barrier),and the gravity(i.e.,in the gravitational environment of the Moon,Earth and Mars),greatly affected the impact behavior of granular flow on a rigid barrier as well.
基金supported by the National Major Science and Technology Project under the 13th Five-year Plan“Development of large oil/gas fields and coalbed methane”(No.:2016ZX05034-002-006 and 2016ZX05066003-003).
文摘When using the plug pulse decay method to measure shale permeability,a comprehensive analysis of various factors influencing the measurement and analysis precision is conducive to improving the accuracy of the test result.A great number of nano-scale pores are developed in shale,so the lower the test pressure is,the more easily the non-Darcy flow tends to emerge.In order to ensure the gas is in the form of Darcy flow in the process of measurement,we put forward the lower pressure limit of Darcy flow in pores according to the definition of Knudsen number.Then,the gas desorption-flow coupling model for the gas flow process during the plug pulse decay measurement was established by considering the effects of gas on the adsorption in organic pores.After the partial differential equation set was solved and derived,the corresponding permeability calculation method was proposed.Finally,after the plug pulse decay measurement,the supporting nitrogen isothermal adsorption test and methane isothermal adsorption test were conducted on shale samples.And the following research results were obtained.First,during the plug pulse decay measurement,the flow of gas in rock samples is one-dimensional linear,so when establishing the flow equation,the gas pseudopressure can be replaced with the gas pressure to simplify the calculation.Second,the adsorption of nitrogen in shale is much less than that of methane in shale,so the influence of nitrogen desorption on the flow is negligible when the pressure difference(i.e.<5%)of upstream and downstream changes within 5%of the initial pore pressure.In conclusion,the available industrial standards don't take into consideration the influence of gas adsorption,but the shale permeability measurement can still satisfy the accuracy requirement.
文摘利用计算机视觉对桥梁结构进行位移测量,常见的方法有特征点算法和光流法。为解决光照变化对光流法的精度影响,以及特征点法难以对目标进行实时跟踪等问题,以定向FAST与旋转BRIEF(oriented FAST and rotated BRIEF,ORB)特征点算法提取目标特征点,并结合LK(Lucas-Kanade)光流法进行跟踪。通过两种算法的互补融合,并设定周期性更新策略,有效减少误差积累。在室内进行了钢板梁模型激振试验,探讨光照变化对算法性能的影响。将算法得到的位移数据与激光位移计测量结果进行对比,以验证其准确性。此外,还将该算法与FAST-LK、SIFT-LK、Shi-Tomasi-LK、siamRPN++等算法进行比对分析。结果表明:该算法得到的位移曲线拟合程度在95%以上,误差控制在5%之内,验证了其可行性,同时,试验表明该方法对光照变化具有一定的鲁棒性,并能达到实时性的要求。
文摘微结构探测器是目前国际上气体探测器研究的热点,但普通微结构探测器的性能无法满足核保障等研究领域对能量分辨的要求。为此团队自主研制了一种高能量分辨MicroMegas探测器。通过建立测试系统对探测器进行测试,发现其性能不仅取决于探测器本身的制作工艺,还与系统的使用及测试方法紧密相关。为充分发挥探测器性能,需要对气体探测器性能影响的各方面因素进行测试与分析,建立数据库,优化测试系统和实验条件。在上述研究基础上,利用^(55)Fe放射源在Ar+5%iC_4H_(10)的气体下对原子能院制作的MicroMegas进行能量分辨测试,在5.9 ke V能量下获得能量分辨的平均值为11.7%,与目前国际上微结构探测器的最好水平持平。通过优化测试系统和实验条件,能够获得更加稳定的探测器性能,更容易在核保障、核物理与辐射探测领域推广。
