Numerical Investigation On Performance Optimization Of Polymer Matrix Composite Tubing In Deep Oil Wells

As the drilling depth of oilfields in Northwest China continues to increase,higher requirements are put forward for the strength and corrosion resistance of tubing.Therefore,finding a method that can improve the mechanical properties of non-metallic tubing has important engineering application value.In this paper,the finite element simulation method is used to study the influence of particles,long fibers and short fibers alone or synergistically on the properties of high temperature resistant bismaleimide resin(MBI)composites,and then the structural strength and sealing of the tubing are researched.First of all,based on the theory of computational micromechanics and ANSYS software to establish models of different schemes,that is,taking the design of multiscale structural composite materials as the starting point,systematically studying the effects of single element(particles,short fibers or long fibers)and multi-element synergistic reinforcement on BMI-based composites.On this basis,a technical solution for multi-element synergistic enhancement of single-layer composite materials is proposed.The study shows that: when single element is reinforced,the content and orientation angle have a greater impact on performance.The mechanical properties are best when 8% particles or 7.5% of short fibers oriented at 45° or long fibers oriented at75° are added;when multiple elements are reinforced,the synergistic enhancement effect of particles and short fibers is more significant.Secondly,three-dimensional shell elements are used to optimize the internal and external structure of the tubing.Particles and short fibers are used to synergistically reinforce the composite material to form an inner layer structure,and the outer layer is a long fiber structure.Based on the research,it is found that the size of the tubing and the laying angle of the outer layer of fibers have a greater impact on the strength of the tubing.For the tubing with a diameter of 73.02 mm,the inner layer of 2 mm and the outer layer of 4 mm are applied at an angle of [±85/±45/15/±85/±45/-15],so that the internal pressure resistance,axial tensile resistance and radial extrusion resistance can reach the optimal state and meet the requirements of working conditions.Finally,the finite element simulation analysis is carried out on the design and optimization of the connection structure of the tubing.The connection mode of the threaded structure is determined,and the ten kinds of threaded threads designed are simulated and analyzed.It is concluded that a rectangular double-sided rounded 1.8°gradient thread with a tooth height and a pitch of 3.175 mm can meet the requirements of tension and tightness.In addition,the maximum stress of the metal joint structure embedded at one end of the composite material in the other solution is 828.8 MPa after strength check and structural optimization,which effectively reduces the stress of the original design joint.