The Optimization Design Of Downhole Restrictor’s Clamping And Sealing System Based On Finite Element Method

As a new method used in oil& gas field development process of large scale and low cost, download throttling method can be very helpful in dealing well with many technical problems of wellbore and surface during oil & gas production process. In design respect the mostly used in field application is 27/8″mobile downhole restrictor which can be set at any depth as needed, seldom causing movement and achieving sealing effect under normal circumstances. During the actual application, because of the high underground pressure, the anchoring force between slips and throttle pipe is very heavy, and there is also a friction problem existing between the sealing rubber cylinder super elastic material and tubing. Accidents caused by downhole throttle slips and rubber tube occur frequently. Consequently,taking 73 mm mobile downhole restrictor as study subjects, using axiomatic design theory and finite element method, this paper introduced the optimization design of process modeling,the analysis of contact stress distribution and structure optimization of clamping mechanism and the sealing mechanism which are the core components of downhole restrictor, the main achievements are as follows:(1)Carrying on the analysis to the structure characteristics and working principle of mobile downhole restrictor; the finite element theory of elastic-plastic contact between the retaining structure and the tubing, and the nonlinear contact problem of the sealing rubber cylinder super elastic material and tubing are also analyzed.(2)Using axiomatic design theory and method, unified modeling to the optimal designing process of clamping mechanism and the sealing rubber cylinder mechanism, so as to effectively backstop the key nodes control and knowledge acquisition.(3)According to axiomatic design, established the finite element model of clamping system, analyzed some important parameters that impact the effect of contact stress, such as the thickness of the slips, thread form angle. In order to effectively reduce the contact stress, the optimal structural scheme can be obtained on the basis of parameter optimization.(4)According to axiomatic design theory, established the finite element contact model of the sealing rubber cylinder super elastic material, analyzed some important parameters that impact the effect of contact stress, such as the length of rubber cylinder, rubber material, the coefficient of friction, and the best approach can be determined on the basis of parameter optimization.This paper provides a new theoretical reason and reference for the solution of mobile downhole restrictor structure optimization, performance analysis, new type restrictor design.