This study aims to elucidate the dynamic evolution mechanism of the fracturing fracture system during the exploration and development of complex oil and gas reservoirs.By integrating methods of rock mechanical testing...This study aims to elucidate the dynamic evolution mechanism of the fracturing fracture system during the exploration and development of complex oil and gas reservoirs.By integrating methods of rock mechanical testing,logging calculation,and seismic inversion technology,we obtained the current insitu stress characteristics of a single well and rock mechanical parameters.Simultaneously,significant controlling factors of rock mechanical properties were analyzed.Subsequently,by coupling hydraulic fracturing physical experiments with finite element numerical simulation,three different fracturing models were configured:single-cluster,double-cluster,and triple-cluster perforations.Combined with acoustic emission technology,the fracture initiation mode and evolution characteristics during the loading process were determined.The results indicate the following findings:(1)The extension direction and length of the fracture are significantly controlled by the direction of the maximum horizontal principal stress.(2)Areas with poor cementation and compactness exhibit complex fracture morphology,prone to generating network fractures.(3)The interlayer development of fracturing fractures is controlled by the strata occurrence.(4)Increasing the displacement of fracturing fluid enlarges the fracturing fracture length and height.This research provides theoretical support and effective guidance for hydraulic fracturing design in tight oil and gas reservoirs.展开更多
An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell ...An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67mA to 0.32mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.展开更多
In the present paper, a three-dimensional （3D） Eulerian technique for the 3D numerical simulation of high-velocity impact problems is proposed. In the Eulerian framework, a complete 3D conservation element and solut...In the present paper, a three-dimensional （3D） Eulerian technique for the 3D numerical simulation of high-velocity impact problems is proposed. In the Eulerian framework, a complete 3D conservation element and solution element scheme for conservative hyperbolic governing equations with source terms is given. A modified ghost fluid method is proposed for the treatment of the boundary conditions. Numerical simulations of the Taylor bar problem and the ricochet phenomenon of a sphere impacting a plate target at an angle of 60~ are carried out. The numerical results are in good agreement with the corresponding experimental observations. It is proved that our computational technique is feasible for analyzing 3D high-velocity impact problems.展开更多
Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,compara...Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,comparatively fewer works have been devoted to study the effect of adsorption boundary layer(ABL)in throats based on the digital rock method.By considering an ABL,we investigate its effects on fluid flow.We build digital rock model based on computed tomography technology.Then,microscopic pore structures are extracted with watershed segmentation and pore geometries are meshed through Delaunay triangulation approach.Finally,using the meshed digital simulation model and finite element method,we investigate the effects of viscosity and thickness of ABL on microscale flow.Our results demonstrate that viscosity and thickness of ABL are major factors that significantly hinder fluid flow in throats.展开更多
In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the sof...In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the software of ANSYS 5 5 are used to carry out the numerical simulation research. The laws of the extrusion pressure changing with the extrusion parameters, such as the die angle, extrusion ratio, and friction coefficient, are obtained. The simulation results are in good agreement with the experimental ones, and the simulated results are believable.展开更多
Aim To study the elastic plastic dynamical constitutive relations about a jointed rock mass under explosion load and its computer simulation. Methods\ Stress history is taken into account and stresses will follow ch...Aim To study the elastic plastic dynamical constitutive relations about a jointed rock mass under explosion load and its computer simulation. Methods\ Stress history is taken into account and stresses will follow changes in time during a period of explosion load. According to the principle of static force balance, the corresponding nodal concentrated force is calculated and the nodal displacement is counted. The elastic plastic dynamic finite element equations are thus obtained. Results\ A finite element method is given for a jointed rock mass under explosion load. Conclusion\ The problem of large plastic deformation for jointed rock mass on blasting was efficiently resolved through dynamic finite element analysis and the range of damages by blasting simulated, and this pushes forward the problem to engineering practice.展开更多
Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-materia...Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-material interfaces is demonstrated. Discontinuous Galerkin finite element method is used to solve Euleri- an equations. And the fifth-order weighted essentially non-oscillatory （WENO） scheme is used to solve the level set equation for capturing multi-material interfaces. The ghost fluid method is used to deal with the interfacial boundary condition. Results are obtained for two bubble interacting with a moving shock. The contours of the constant density and the pressure at different time are given. In the computational domain, three different cases are considered, i.e. two helium bubbles, a helium bubble followed by an R22 bubble in the direction of the moving shock, and an R22 bubble followed by a helium bubble. Computational results indicate that multi-mate- rial interfaces can be properly captured by the level set method. Therefore, for problems involving the flow of three different materials with two different interfaces, each interface separating two different materials can be similarly handled.展开更多
The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electr...The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.展开更多
Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during d...Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during drilling, lost circulation may occur and result in a change to the original formation temperature field, and in severe cases, even the conventional open hole well logging data cannot be obtained. This paper uses finite element analysis software COMSOL to establish a heat transfer model for the wellbore/reservoir formation system during drilling and shut-in in the presence of lost circulation, and a case study is made in a carbonate reservoir in the Tahe oilfield. On the basis of the above, we analyze the temperature distribution in the leakage zone, and the studies have shown that the leakage and petrophysical properties have an impact on the temperature of the wellbore and formation, hence we can estimate the reservoir permeability using the temperature data. In addition, the determination of the temperature recovery time after some drilling fluids have leaked into the formation will help in recognizing the subsurface temperature field of the carbonate formation correctly, thus enhancing production logging interpretation accuracy and improving the understanding of later measurements.展开更多
Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and ...Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.展开更多
A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching a...A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching and forming process of cartridge cases are established,and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus,a 3D annotation module is developed with secondary development technology of UG NX software. Consequently,the final process model with dimension and process information is obtained. Then,with the current 3D process management system,the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%,which proves the validity and reliability of the proposed method in this study.展开更多
Fracture and ground vibration of rock subjected to different decoupling decked charges are investigated based on the numerical simulation. The dynamic pressure value is studied, which demonstrates that simulation of f...Fracture and ground vibration of rock subjected to different decoupling decked charges are investigated based on the numerical simulation. The dynamic pressure value is studied, which demonstrates that simulation of fracture zone is feasible. Attenuation index of dynamic pressure is 2.06, 2.05 and 1.93 for air, water and sand intervals respectively. The small attenuation of sand in- terval results in the large ground vibration. The predicted vertical vibration waveform and peak parti- cle velocities （PPV） in far-field are in agreement with the monitoring results. The results show that the air and water decked charges can improve the effect of rock fracture in near-field and reduce ground vibration in far-field.展开更多
为准确预报船舶在不同厚度海冰下的阻力性能,基于FEM/SPH(Finite Element Method/Smoothed Particle Hydrodynamics)耦合方法开展不同冰级船舶冰阻力预报研究。采用线弹性与非线性软化相结合的方式构建黏聚单元损伤模型,以冰层厚度为基...为准确预报船舶在不同厚度海冰下的阻力性能,基于FEM/SPH(Finite Element Method/Smoothed Particle Hydrodynamics)耦合方法开展不同冰级船舶冰阻力预报研究。采用线弹性与非线性软化相结合的方式构建黏聚单元损伤模型,以冰层厚度为基础尺寸建立海冰数值模型,通过弯曲强度测试标定相应的力学参数。同时,考虑船舶破冰过程中海水的影响,分别选择低冰级、中冰级和高冰级极地船舶开展破冰过程数值模拟并预报船舶冰阻力。将冰阻力数值计算结果与模型试验结果相对比,结果表明二者的最大偏差不超过12%,证明该数值预报方法可行。展开更多
基金supported by the Major Scientific and Technological Projects of CNPC under grant ZD2019-183-006the National Science and Technology Major Project of China(2016ZX05014002-006)the National Natural Science Foundation of China(42072234)。
文摘This study aims to elucidate the dynamic evolution mechanism of the fracturing fracture system during the exploration and development of complex oil and gas reservoirs.By integrating methods of rock mechanical testing,logging calculation,and seismic inversion technology,we obtained the current insitu stress characteristics of a single well and rock mechanical parameters.Simultaneously,significant controlling factors of rock mechanical properties were analyzed.Subsequently,by coupling hydraulic fracturing physical experiments with finite element numerical simulation,three different fracturing models were configured:single-cluster,double-cluster,and triple-cluster perforations.Combined with acoustic emission technology,the fracture initiation mode and evolution characteristics during the loading process were determined.The results indicate the following findings:(1)The extension direction and length of the fracture are significantly controlled by the direction of the maximum horizontal principal stress.(2)Areas with poor cementation and compactness exhibit complex fracture morphology,prone to generating network fractures.(3)The interlayer development of fracturing fractures is controlled by the strata occurrence.(4)Increasing the displacement of fracturing fluid enlarges the fracturing fracture length and height.This research provides theoretical support and effective guidance for hydraulic fracturing design in tight oil and gas reservoirs.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDA09020402the National Integrate Circuit Research Program of China under Grant No 2009ZX02023-003+1 种基金the National Natural Science Foundation of China under Grant Nos 61261160500,61376006,61401444 and 61504157the Science and Technology Council of Shanghai under Grant Nos 14DZ2294900,15DZ2270900 and 14ZR1447500
文摘An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67mA to 0.32mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10732010,10972010,and 11332002)
文摘In the present paper, a three-dimensional （3D） Eulerian technique for the 3D numerical simulation of high-velocity impact problems is proposed. In the Eulerian framework, a complete 3D conservation element and solution element scheme for conservative hyperbolic governing equations with source terms is given. A modified ghost fluid method is proposed for the treatment of the boundary conditions. Numerical simulations of the Taylor bar problem and the ricochet phenomenon of a sphere impacting a plate target at an angle of 60~ are carried out. The numerical results are in good agreement with the corresponding experimental observations. It is proved that our computational technique is feasible for analyzing 3D high-velocity impact problems.
基金National Natural Science Foundation of China(No.51674280,51774308,51704033,51722406,51950410591)Shandong Provincial Natural Science Foundation(ZR2019JQ21,JQ201808)+3 种基金the Fundamental Research Funds for the Central Universities(No.20CX02113A)National Science and Technology Major Project(2016ZX05014-000407)Program for Changjiang Scholars and Innovative Research Team in University(IRT_16R69)PetroChina Innovation Foundation(No.2018D-5007-0210)。
文摘Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,comparatively fewer works have been devoted to study the effect of adsorption boundary layer(ABL)in throats based on the digital rock method.By considering an ABL,we investigate its effects on fluid flow.We build digital rock model based on computed tomography technology.Then,microscopic pore structures are extracted with watershed segmentation and pore geometries are meshed through Delaunay triangulation approach.Finally,using the meshed digital simulation model and finite element method,we investigate the effects of viscosity and thickness of ABL on microscale flow.Our results demonstrate that viscosity and thickness of ABL are major factors that significantly hinder fluid flow in throats.
文摘In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the software of ANSYS 5 5 are used to carry out the numerical simulation research. The laws of the extrusion pressure changing with the extrusion parameters, such as the die angle, extrusion ratio, and friction coefficient, are obtained. The simulation results are in good agreement with the experimental ones, and the simulated results are believable.
文摘Aim To study the elastic plastic dynamical constitutive relations about a jointed rock mass under explosion load and its computer simulation. Methods\ Stress history is taken into account and stresses will follow changes in time during a period of explosion load. According to the principle of static force balance, the corresponding nodal concentrated force is calculated and the nodal displacement is counted. The elastic plastic dynamic finite element equations are thus obtained. Results\ A finite element method is given for a jointed rock mass under explosion load. Conclusion\ The problem of large plastic deformation for jointed rock mass on blasting was efficiently resolved through dynamic finite element analysis and the range of damages by blasting simulated, and this pushes forward the problem to engineering practice.
基金Supported by the National Natural Science Foundation of China(10476011)~~
文摘Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-material interfaces is demonstrated. Discontinuous Galerkin finite element method is used to solve Euleri- an equations. And the fifth-order weighted essentially non-oscillatory （WENO） scheme is used to solve the level set equation for capturing multi-material interfaces. The ghost fluid method is used to deal with the interfacial boundary condition. Results are obtained for two bubble interacting with a moving shock. The contours of the constant density and the pressure at different time are given. In the computational domain, three different cases are considered, i.e. two helium bubbles, a helium bubble followed by an R22 bubble in the direction of the moving shock, and an R22 bubble followed by a helium bubble. Computational results indicate that multi-mate- rial interfaces can be properly captured by the level set method. Therefore, for problems involving the flow of three different materials with two different interfaces, each interface separating two different materials can be similarly handled.
文摘The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.
文摘Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during drilling, lost circulation may occur and result in a change to the original formation temperature field, and in severe cases, even the conventional open hole well logging data cannot be obtained. This paper uses finite element analysis software COMSOL to establish a heat transfer model for the wellbore/reservoir formation system during drilling and shut-in in the presence of lost circulation, and a case study is made in a carbonate reservoir in the Tahe oilfield. On the basis of the above, we analyze the temperature distribution in the leakage zone, and the studies have shown that the leakage and petrophysical properties have an impact on the temperature of the wellbore and formation, hence we can estimate the reservoir permeability using the temperature data. In addition, the determination of the temperature recovery time after some drilling fluids have leaked into the formation will help in recognizing the subsurface temperature field of the carbonate formation correctly, thus enhancing production logging interpretation accuracy and improving the understanding of later measurements.
文摘Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.
基金Supported by the National Defense Basic Scientific Research Project(A1020131011)
文摘A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching and forming process of cartridge cases are established,and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus,a 3D annotation module is developed with secondary development technology of UG NX software. Consequently,the final process model with dimension and process information is obtained. Then,with the current 3D process management system,the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%,which proves the validity and reliability of the proposed method in this study.
文摘Fracture and ground vibration of rock subjected to different decoupling decked charges are investigated based on the numerical simulation. The dynamic pressure value is studied, which demonstrates that simulation of fracture zone is feasible. Attenuation index of dynamic pressure is 2.06, 2.05 and 1.93 for air, water and sand intervals respectively. The small attenuation of sand in- terval results in the large ground vibration. The predicted vertical vibration waveform and peak parti- cle velocities （PPV） in far-field are in agreement with the monitoring results. The results show that the air and water decked charges can improve the effect of rock fracture in near-field and reduce ground vibration in far-field.
文摘为准确预报船舶在不同厚度海冰下的阻力性能,基于FEM/SPH(Finite Element Method/Smoothed Particle Hydrodynamics)耦合方法开展不同冰级船舶冰阻力预报研究。采用线弹性与非线性软化相结合的方式构建黏聚单元损伤模型,以冰层厚度为基础尺寸建立海冰数值模型,通过弯曲强度测试标定相应的力学参数。同时,考虑船舶破冰过程中海水的影响,分别选择低冰级、中冰级和高冰级极地船舶开展破冰过程数值模拟并预报船舶冰阻力。将冰阻力数值计算结果与模型试验结果相对比,结果表明二者的最大偏差不超过12%,证明该数值预报方法可行。
