| The packer is an important downhole tool used in oilfield operation.Its function is to seal the annulus zones,isolate production zones and control the injected and produced fluid,and its sealing elements is one of the core components to achieve this function.Conventional packers use a rubber as its sealing element.As oilfield tends to mine the oil of deep wells,the rubber elements of conventional packers can be damaged in deep wells with high temperature,high pressures and corrosion,which causes the seal failure.Metal materials have strong advantages under condition of deep well.Therefore,the introduction of metal sealing technology into packers is a new way to solve above problems.In addition,research on metal seal packers is not yet in-depth.Therefore,the further study of the metal sealing technology of packers is of great significance for the development of metal packers and the reduction of the oilfield.The main research contents and conclusions are as follows:(1)From the microscopic point of view,the sealing mechanism of the packer sealing element was analyzed,and the working principle of the packer of QSA-114 model was analyzed.It is found that the metal sealing surface needs to have a certain plastic deformation to fill the leakage channel to form a continuous sealing tape,and the sealing surface is coated with soft metal to improve the sealing performance.Then,combined with the sealing mechanism and functional characteristics of the sealing element,a new type of packer metal sealing element was designed and its structural stress was analyzed.The results show that the setting force of the sealing element increases as the arch radius increases.(2)The constitutive model of NiTi alloy was analyzed.The material library and numerical model of standard tensile specimen were established in Workbench based on the experimental data.By comparing the simulation and experimental results,the reliability of the constitutive model and the feasibility of the simulation modeling method are verified,which can provide basis for subsequent simulation analysis.(3)Firstly,through the simplification of the geometric model,the numerical model of the seal assembly was established in Workbench.After calculation,the results show that the sealing element meet the requirements of use.Then,the influence of the external pressure of the sealing element was studied under five working conditions.The internal pressure was introduced to eliminate the influence of the external pressure.It is found that the external pressure causes the sealing elements to be distorted to varying extents,resulting in failure to seal.After the internal pressure is introduced,the two cancel each other out,and the performance of the sealing elements is similar to that of no internal and external pressure.Finally,the influence of the structural parameters of the sealing element on its sealing performance was studied by a single factor method.The results show that the height of the bearing ring has almost no influence,the influence of other structural parameters can be followed regularly,which can provide reference for the design of the sealing element,especially considering the influence of the arch radius and the arch thickness.(4)Firstly,by analyzing the engineering application background and application requirements of the metal sealing components of the packer,the optimization objectives and constraints were determined.Secondly,based on Workbench and Isight,the sensitivity of the structural parameters of the sealing element was analyzed,and a joint simulation optimization model was established.The optimization has obtained the sealing elements with excellent performance,and the performance of them are better than that before optimization.Then,the characteristics of them in the process of setting and unloading were studied.It is found that the four sealing elements have different degrees of jitter during the process,but the jitter of No.8 is smaller and its performance is better.Finally,the failure conditions and causes of the sealing elements were analyzed,and the measures and suggestions were given. |
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