Mechanical Analysis & Experimental Research On Valvular Slip

Packers are commonly used tools in the oilfield development. Their qualities and reliability will directly affect the oilfield development's cost. The slips are very important parts in the packers, whose working performance directly influences the packers'performance. Therefore, the packer slips'mechanical analysis and experimental research can effectively reduce the production cost, increase the working efficiency, and enhance the working reliability. The studies on the packer slips have become the research focus of many oilfield companies in the world.With the main reservoirs in China have entered into the medium or high water cut period and the discovery of many oilfields with deep wells and super deep wells, the packer's performance and its accessories needs to have new and higher requirements---that is temperature resistance, pressure resistance and running depth need to be improved. During the field operation, some problems usually take places, such as packers'unstable setting, slips easily broken and casing damage. The reasons are mainly due to the unreasonable design on the packer slips. As a result, it is urgent to do the mechanical analysis and optimum design for the slips and to study the stress distribution laws of packer slips and casing. Consequently, the best structure for packers can be optimized. This paper combines basic theory studies with experimental research with application technologies. A new design way for optimizing the packers'structure has been constructed, which can improve the packers'design level and promote the relevant subjects development.The paper is involved in many subjects, for instance, elastic mechanics, plastic mechanics, experimental mechanics, photo-elastic theory, similar theory, and non-linear FEA. At the same time, it includes many disciplines about metal structure relation, such as multiple coupling problems about material non-linearity, contact non-linearity and transient dynamics. By the mechanical analysis, mechanical model and finite element model of packer's slip are set up in this paper. Conservation equation and transient dynamics balance equation of packer's slip are set up by using momentum theorem and dynamics principle in the scope of finite distortion. Non-embed measurement equation of contact surface is derived from the slip's structure parameters and movement condition. The weak style of balance equation is derived from variation principle and updated Lagrange format. Adopting augmented Lagrange multiplier method sets up the interface's momentum equation between slips and casing. At last, the force and deformation state of packers are calculated on the conditions of multiple coupling by using FEA (finite element analysis) method, load increment method, augmented Lagrange multiplier method, and Newmark method.The force of packers and casing and the occlusive force distribution laws are found out by force analysis and experimental research, which establish the theory basis for optimizing slips. In the process of optimizing slips, the computing results should be confirmed firstly with the change of slips'each relative parameter. Then by comparing each structure parameter, such as the equivalent friction coefficient between slips and casing, the maximum Von Mises stress, contacting radial stress and so on, the each slip's optimum structure parameters are determined. At last, the optimum structure parameters of slips are confirmed by orthogonalizing each parameter. All of those studies provide new ideas and methods for optimizing packers and similar tools.Although the function of numerical calculation method becomes stronger and the precision of computing results are reliable, the numerical calculation is not enough for setting up the model and the boundary condition, which also need to be confirmed by the experimental stress analysis technology. Photo-elasticity experiment is adopted to simulate the packers'component model in order to verify the correctness of results. The stress distributing law of slips and casing in computing model is comparatively consistent with that in experimental model after comparing the experimental results with the computing results. Moreover, the two model results are coincident when the frictional coefficient in computing model is equal to 0.28.The optimum methods put forward in the paper are good guidance for the new problems arising from the oilfield development. The achieved results provide the theoretical basis in designing packers, which guarantee packers'working operation, prolonging duty cycle, increasing production rate and reducing production costs. The significance of increasing oilfield economic benefits is quite clearly.