针对致密砂岩气藏在开发过程中,存在采收率低,气井产水现象严重的问题。本文从致密砂岩气藏气水两相渗流规律着手,采用CT扫描技术识别二维裂缝,并利用FLUENT数值模拟软件,模拟不同压差下致密砂岩气藏的气水两相渗流规律。结果表明:残余...针对致密砂岩气藏在开发过程中,存在采收率低,气井产水现象严重的问题。本文从致密砂岩气藏气水两相渗流规律着手,采用CT扫描技术识别二维裂缝,并利用FLUENT数值模拟软件,模拟不同压差下致密砂岩气藏的气水两相渗流规律。结果表明:残余气分布主要分布在不连通的裂隙之中,少部分气体分布在连通裂缝之中;增大压差,气水分布变化,采收率略微提高;缝网越发育,采出程度越小,最终采收率提高程度越小。建议在致密砂岩气藏开采的过程中,可以采取前期增大压差,后期降低废弃压力的方式,使得致密砂岩气藏可以获得较大的产能。研究结果对于致密砂岩气藏开发具有一定的指导意义。Aiming at the tight sandstone gas reservoirs in the development process, there are problems of low recovery rate and serious water production phenomena in gas wells. In this paper, we start from the gas-water two-phase seepage law of tight sandstone gas reservoirs, use CT scanning technology to identify two-dimensional fractures and use FLUENT numerical simulation software to simulate the gas-water two-phase seepage law of tight sandstone gas reservoirs under different pressure differences. The results show that: the residual gas distribution is mainly distributed in the disconnected fractures, and a small portion of the gas is distributed in the connected fractures;increasing the pressure difference, the gas-water distribution changes, and the recovery rate is slightly increased;the more the fracture network is developed, the smaller the degree of extraction is, and the smaller the degree of increase in the final recovery rate is. It is suggested that when mining tight sandstone gas reservoirs, the method of increasing the differential pressure in the early stage and decreasing the waste pressure in the later stage can be adopted so that the tight sandstone gas reservoirs can obtain a larger production capacity. The results of the study have a certain guiding significance for the development of tight sandstone gas reservoirs.展开更多
In this study,the effect of varied loading ratio(mass of the explosive/mass of flyer plate)on the nature of interface,temperature and pressure developed in aluminum-steel explosive cladding is presented.Increase in th...In this study,the effect of varied loading ratio(mass of the explosive/mass of flyer plate)on the nature of interface,temperature and pressure developed in aluminum-steel explosive cladding is presented.Increase in the loading ratio,R,enhances the pressure developed,kinetic energy utilization and deformation work performed.Interfacial microstructures exhibit the formation of molten layer at few spots,owing to the increase in temperature beyond the melting point of parent alloy.The increase in temperature and the quantum of pressure developed were determined by numerical simulation performed in Ansys AUTODYN by employing smoothed particle hydrodynamics(SPH)method.The positioning of the experimental conditions on the weldability window is presented as well.展开更多
A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.Th...A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.The components of ES forming die were manufactured and installed to Gleeble1500D thermo-mechanical simulator.The microstructure observations were carried out on the as-extruded rods(as-received) and ES formed rods.From the simulation results,ES forming can increase the cumulative strain enormously and the volume fraction of dynamic recrystallization.From the physical modeling results,the microstructures can be refined.展开更多
Combining with the indoor clogging tests of loose foundation in Tibet,the permeability clogging process of loose foundation was simulated based on particle flow method. Under the constant head of 2.2m, numerical micro...Combining with the indoor clogging tests of loose foundation in Tibet,the permeability clogging process of loose foundation was simulated based on particle flow method. Under the constant head of 2.2m, numerical micro-simulation was made in three cases,which was not adding any clogging materials,or adding the clogging materials with the diameter between 0.075-0.500 mm and 0.5-1 mm. The dynamic changes of fluid velocity,permeability coefficient,porosity and loss amount were recorded in the numerical simulation. The results have shown that fluid velocity and permeability coefficient decreased rapidly,when adding the clogging materials with the diameter between 0.5 mm and 1.0 mm. With seepage stability,fluid velocity value was very low. By using computer simulation in the two cases,we got that both cases induced clogging effect. Clogging effect was due to one of the interval of particles rather than one size,which could be seen in the phenomenon of the second case. To some extent,numerical method is useful in the study of clogging problems,which gave the same result obtained in laboratory test and simulation test. These data provided basis and reference for further study of clogging problems,and also provided a new method to study the micro-scale permeability clogging mechanism.展开更多
Based on the assumption of laminated microstructure, a micromechanical model of stress induced martensite transformation for NiTi shape memory alloys single crystal is proposed. Elasticity anisotropy and different pro...Based on the assumption of laminated microstructure, a micromechanical model of stress induced martensite transformation for NiTi shape memory alloys single crystal is proposed. Elasticity anisotropy and different proper-ties for two phases are considered. Martensite volume fraction is chosen as the internal variable that controls the phase transformation quantitatively. An effective macroscopic elasticity matrix based on the different elasticity characteristics of each phase and the martensite volume fraction are obtained with the help of the perfect interfa-cial relationships. A phase transformation driving force is derived to construct the transformation criterion. The model corresponds to a non-convexity free energy function during phase transformation, so softening behavior can be well simulated by the model. A numerical simulation is implemented for the uniaxial loading of NiTi single crystal alloy according to the model, and simulation results are proved by experimental results of polycrystal with strong {111} texture. Superelasticity, Anisotropy, the evolution of microstructure and softening behavior can be well simulated.展开更多
文摘针对致密砂岩气藏在开发过程中,存在采收率低,气井产水现象严重的问题。本文从致密砂岩气藏气水两相渗流规律着手,采用CT扫描技术识别二维裂缝,并利用FLUENT数值模拟软件,模拟不同压差下致密砂岩气藏的气水两相渗流规律。结果表明:残余气分布主要分布在不连通的裂隙之中,少部分气体分布在连通裂缝之中;增大压差,气水分布变化,采收率略微提高;缝网越发育,采出程度越小,最终采收率提高程度越小。建议在致密砂岩气藏开采的过程中,可以采取前期增大压差,后期降低废弃压力的方式,使得致密砂岩气藏可以获得较大的产能。研究结果对于致密砂岩气藏开发具有一定的指导意义。Aiming at the tight sandstone gas reservoirs in the development process, there are problems of low recovery rate and serious water production phenomena in gas wells. In this paper, we start from the gas-water two-phase seepage law of tight sandstone gas reservoirs, use CT scanning technology to identify two-dimensional fractures and use FLUENT numerical simulation software to simulate the gas-water two-phase seepage law of tight sandstone gas reservoirs under different pressure differences. The results show that: the residual gas distribution is mainly distributed in the disconnected fractures, and a small portion of the gas is distributed in the connected fractures;increasing the pressure difference, the gas-water distribution changes, and the recovery rate is slightly increased;the more the fracture network is developed, the smaller the degree of extraction is, and the smaller the degree of increase in the final recovery rate is. It is suggested that when mining tight sandstone gas reservoirs, the method of increasing the differential pressure in the early stage and decreasing the waste pressure in the later stage can be adopted so that the tight sandstone gas reservoirs can obtain a larger production capacity. The results of the study have a certain guiding significance for the development of tight sandstone gas reservoirs.
文摘In this study,the effect of varied loading ratio(mass of the explosive/mass of flyer plate)on the nature of interface,temperature and pressure developed in aluminum-steel explosive cladding is presented.Increase in the loading ratio,R,enhances the pressure developed,kinetic energy utilization and deformation work performed.Interfacial microstructures exhibit the formation of molten layer at few spots,owing to the increase in temperature beyond the melting point of parent alloy.The increase in temperature and the quantum of pressure developed were determined by numerical simulation performed in Ansys AUTODYN by employing smoothed particle hydrodynamics(SPH)method.The positioning of the experimental conditions on the weldability window is presented as well.
基金Project(2007CB613700) supported by the National Basic Research Program of ChinaProject(2007BAG06B04) supported by the National Science and Technology Pillar Program during the 11th Five-Year Plan Period+1 种基金Project(50725413) supported by the National Natural Science Foundation of ChinaProject(CSTC2009AB4008) supported by Chongqing Science and Technology Development Program,China
文摘A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.The components of ES forming die were manufactured and installed to Gleeble1500D thermo-mechanical simulator.The microstructure observations were carried out on the as-extruded rods(as-received) and ES formed rods.From the simulation results,ES forming can increase the cumulative strain enormously and the volume fraction of dynamic recrystallization.From the physical modeling results,the microstructures can be refined.
基金supported by the National Natural Science Foundation of P. R. China,clogging effects on affects and mechanism of the permeability of loose medium of altitude reservoirs (No. 41072197)
文摘Combining with the indoor clogging tests of loose foundation in Tibet,the permeability clogging process of loose foundation was simulated based on particle flow method. Under the constant head of 2.2m, numerical micro-simulation was made in three cases,which was not adding any clogging materials,or adding the clogging materials with the diameter between 0.075-0.500 mm and 0.5-1 mm. The dynamic changes of fluid velocity,permeability coefficient,porosity and loss amount were recorded in the numerical simulation. The results have shown that fluid velocity and permeability coefficient decreased rapidly,when adding the clogging materials with the diameter between 0.5 mm and 1.0 mm. With seepage stability,fluid velocity value was very low. By using computer simulation in the two cases,we got that both cases induced clogging effect. Clogging effect was due to one of the interval of particles rather than one size,which could be seen in the phenomenon of the second case. To some extent,numerical method is useful in the study of clogging problems,which gave the same result obtained in laboratory test and simulation test. These data provided basis and reference for further study of clogging problems,and also provided a new method to study the micro-scale permeability clogging mechanism.
基金supported by the National Natural Science Foundation of China(Grant No.10602011)the Key Project of Chinese National Programs for Fundamental Research and Development(Grant No.2012CB619603)the Fundamental Research Funds for the Central Universities(Grant No.DUT10LK42)
文摘Based on the assumption of laminated microstructure, a micromechanical model of stress induced martensite transformation for NiTi shape memory alloys single crystal is proposed. Elasticity anisotropy and different proper-ties for two phases are considered. Martensite volume fraction is chosen as the internal variable that controls the phase transformation quantitatively. An effective macroscopic elasticity matrix based on the different elasticity characteristics of each phase and the martensite volume fraction are obtained with the help of the perfect interfa-cial relationships. A phase transformation driving force is derived to construct the transformation criterion. The model corresponds to a non-convexity free energy function during phase transformation, so softening behavior can be well simulated by the model. A numerical simulation is implemented for the uniaxial loading of NiTi single crystal alloy according to the model, and simulation results are proved by experimental results of polycrystal with strong {111} texture. Superelasticity, Anisotropy, the evolution of microstructure and softening behavior can be well simulated.
