Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations,a three-dimensional(3D)numerical simulation scheme is proposed.The three-dimensional finite element software i...Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations,a three-dimensional(3D)numerical simulation scheme is proposed.The three-dimensional finite element software is used to analyze the mechanical behavior of fractures and the pressure sealing process,and evaluate the stress cage effect.The main features of the model are as follows:(1)The equivalent fractures in the analytical model represent the function sum of the mechanical behavior of all fractures on the well wall,which is a functionally equivalent crack.(2)When evaluating the stress cage effect,the shape of the crack wedge filled with the plugging agent particles is formed by simulating the fractures opening process under the injection pressure,not a given regular shape.(3)In the model of calculating bull heading of block agent,the liquid pressure on the well wall is the injection pressure,which is a variation increased with time.The fluid pressure on the well wall in the stress cage calculation model is generated by the initial pore pressure.(4)The numerical evaluation of the stress cage effect is achieved by calculating the increase amplitude FX of the minimum hoop stress on the well wall.Using this model,several sets of injection pressure design values can be used for pressure plugging numerical simulation and stress cage effect evaluation calculation,and then the optimal and accurate quantitative value of“injection pressure,block agent particle size,safe mud window upper bound”are found through comparison.Finally,through an engineering example of horizontal well drilling pressure sealing in a shale gas reservoir developed by a fracture,we use the above theoretical tools to introduce the process and results of the numerical analysis of the extended mud window drilled in the shale gas fissure reservoir.展开更多
目的:对腰椎单、双Cage置入加椎弓根钉内固定两种手术方法的生物力学进行比较,判断上述两种手术方法在生物力学上的优劣。方法:选取正常青壮年男性新鲜尸体的L4/5脊柱标本一具,进行横切扫描,利用三维重建软件M im ics建立椎弓根钉内固...目的:对腰椎单、双Cage置入加椎弓根钉内固定两种手术方法的生物力学进行比较,判断上述两种手术方法在生物力学上的优劣。方法:选取正常青壮年男性新鲜尸体的L4/5脊柱标本一具,进行横切扫描,利用三维重建软件M im ics建立椎弓根钉内固定有限元模型(模型1),单融合器置入加椎弓根螺钉内固定有限元模型(模型2)和双枚融合器植入加椎弓根螺钉内固定有限元模型(模型3);然后在模型上施加压缩、前屈、后伸载荷并测定在各种情况下螺钉和融合器上的应力,结果在excel软件上进行统计分析。结果:在所测的运动状态中,模型1的螺钉应力明显高于模型2和模型3(P<0.05),而模型2与模型3的螺钉应力的差异没有统计学意义(P>0.05);模型2的融合器压力高于模型3,其中在前屈及压缩状态下两者的差别有统计学意义(P<0.05),而后伸状态下差别无统计学意义(P>0.05)。结论:在所测的运动状态下,上述两种手术方法在生物力学上差异无显著性,应用椎弓根螺钉内固定加后路单枚椎间融合器斜行置入进行腰椎内固定融合的手术方法是可行的。展开更多
以应力封闭壳理论为基础,对花岗岩介质中地下强爆炸产生的应力封闭壳效应进行了数值模拟。以100 t TNT当量的强爆炸为例,模拟了爆后空腔的回弹和封闭壳的动态形成过程,给出了形成稳定封闭壳后的径向应力、环向应力和爆心距的关系。计算...以应力封闭壳理论为基础,对花岗岩介质中地下强爆炸产生的应力封闭壳效应进行了数值模拟。以100 t TNT当量的强爆炸为例,模拟了爆后空腔的回弹和封闭壳的动态形成过程,给出了形成稳定封闭壳后的径向应力、环向应力和爆心距的关系。计算了不同爆炸当量形成的应力封闭壳尺寸及其形成时间与爆炸当量的关系。计算结果表明,当空腔膨胀到最大尺寸之后,空腔开始回弹,此时开始形成应力封闭壳;当空腔回弹结束即形成稳定的空腔尺寸时,稳定的应力封闭壳也在该时刻形成;爆炸当量越大,形成的应力封闭壳的范围越大,当爆炸当量低于10 t TNT时,不能形成应力封闭壳。展开更多
基金the general project of national natural science foundation of China(11272216)for the financial support of this paper.
文摘Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations,a three-dimensional(3D)numerical simulation scheme is proposed.The three-dimensional finite element software is used to analyze the mechanical behavior of fractures and the pressure sealing process,and evaluate the stress cage effect.The main features of the model are as follows:(1)The equivalent fractures in the analytical model represent the function sum of the mechanical behavior of all fractures on the well wall,which is a functionally equivalent crack.(2)When evaluating the stress cage effect,the shape of the crack wedge filled with the plugging agent particles is formed by simulating the fractures opening process under the injection pressure,not a given regular shape.(3)In the model of calculating bull heading of block agent,the liquid pressure on the well wall is the injection pressure,which is a variation increased with time.The fluid pressure on the well wall in the stress cage calculation model is generated by the initial pore pressure.(4)The numerical evaluation of the stress cage effect is achieved by calculating the increase amplitude FX of the minimum hoop stress on the well wall.Using this model,several sets of injection pressure design values can be used for pressure plugging numerical simulation and stress cage effect evaluation calculation,and then the optimal and accurate quantitative value of“injection pressure,block agent particle size,safe mud window upper bound”are found through comparison.Finally,through an engineering example of horizontal well drilling pressure sealing in a shale gas reservoir developed by a fracture,we use the above theoretical tools to introduce the process and results of the numerical analysis of the extended mud window drilled in the shale gas fissure reservoir.
文摘目的:对腰椎单、双Cage置入加椎弓根钉内固定两种手术方法的生物力学进行比较,判断上述两种手术方法在生物力学上的优劣。方法:选取正常青壮年男性新鲜尸体的L4/5脊柱标本一具,进行横切扫描,利用三维重建软件M im ics建立椎弓根钉内固定有限元模型(模型1),单融合器置入加椎弓根螺钉内固定有限元模型(模型2)和双枚融合器植入加椎弓根螺钉内固定有限元模型(模型3);然后在模型上施加压缩、前屈、后伸载荷并测定在各种情况下螺钉和融合器上的应力,结果在excel软件上进行统计分析。结果:在所测的运动状态中,模型1的螺钉应力明显高于模型2和模型3(P<0.05),而模型2与模型3的螺钉应力的差异没有统计学意义(P>0.05);模型2的融合器压力高于模型3,其中在前屈及压缩状态下两者的差别有统计学意义(P<0.05),而后伸状态下差别无统计学意义(P>0.05)。结论:在所测的运动状态下,上述两种手术方法在生物力学上差异无显著性,应用椎弓根螺钉内固定加后路单枚椎间融合器斜行置入进行腰椎内固定融合的手术方法是可行的。
文摘以应力封闭壳理论为基础,对花岗岩介质中地下强爆炸产生的应力封闭壳效应进行了数值模拟。以100 t TNT当量的强爆炸为例,模拟了爆后空腔的回弹和封闭壳的动态形成过程,给出了形成稳定封闭壳后的径向应力、环向应力和爆心距的关系。计算了不同爆炸当量形成的应力封闭壳尺寸及其形成时间与爆炸当量的关系。计算结果表明,当空腔膨胀到最大尺寸之后,空腔开始回弹,此时开始形成应力封闭壳;当空腔回弹结束即形成稳定的空腔尺寸时,稳定的应力封闭壳也在该时刻形成;爆炸当量越大,形成的应力封闭壳的范围越大,当爆炸当量低于10 t TNT时,不能形成应力封闭壳。
