Study On Series Structure Design And Mechanical Properties Of Honeycomb Skeleton Inside Bridge Plug Rubber

During downhole work,bridge plug rubber may be damaged due to stress concentration,stress relaxation and oxidation aging,which leads to seal failure.In order to solve this problem,a method of replacing the solid structure of the original rubber with honeycomb skeleton structure is proposed in this thesis.Honeycomb structure not only has the advantages of high specific strength,good energy absorption,but also can provide a larger compression stroke in the setting process of the rubber,so as to improve the sealing performance of the rubber.In this thesis,experimental and numerical simulation methods are used to analyze the pressure performance of series honeycomb structure,and study the influence of dislocation distance,dislocation angle,layer material and thickness and cell parameters on it.Optimize the structure parameters of honeycomb skeleton,design the arrangement mode of honeycomb structure in bridge plug rubber,and study the sealing performance of bridge plug rubber with series honeycomb structure.The dissolution rate of TPU rubber material was measured experimentally,and the model for calculating the dissolution time of the bridge stopper with series honeycomb structure was established.The three-dimensional model in the previous thesis was taken as an example to calculate the dissolution time of the rubber stopper.Specific research contents and related conclusions are as follows:(1)Compression specimens of TPU series honeycomb structure were prepared by 3D printing technology,and quasi-static compression experiments were carried out by PLD-300 fatigue testing machine;At the same time,using ABAQUS software,the influence of dislocation mode,interlayer properties and cell parameters on the pressure-bearing performance of series honeycomb structure is analyzed.Honeycomb skeleton has periodic topological structure and good symmetry,and the change of pressure-bearing performance of honeycomb skeleton caused by dislocation also has periodic and symmetry.The results show that the deformation mode of series honeycomb structure is consistent with the finite element simulation results,and the maximum error of the average platform stress between them is less than 4%;Compared with the single-layer honeycomb skeleton structure,the average platform stress of series honeycomb structure increases by 23.4%;When the series honeycomb structure has translational dislocation or rotational dislocation,the peak strain of the series honeycomb structure is basically the same in half dislocation period,but the peak stress and average platform stress increase with the increase of dislocation distance or dislocation angle;When multi-layer honeycomb skeletons are stacked up and down,the average platform stress of series honeycomb skeletons increases with the increase of interlayer thickness,and the influence of dislocation distance on the average platform stress of series honeycomb skeletons decreases with the increase of interlayer thickness;For rubber,aluminum alloy and structural steel interlayer,the average platform stress of honeycomb framework series structure changes less and less.When the interlayer is made of structural steel,the average platform stress of honeycomb framework series structure does not change greatly with the change of dislocation,and basically stabilizes at 1.68 MPa.Compared with rubber interlayer,the average platform stress decreases by 34.2%,indicating that the greater the stiffness of interlayer,the less sensitive the double-layer rubber honeycomb framework is to the dislocation of upper and lower honeycomb framework,and the lower the average platform stress of honeycomb framework series structure;The variation of average platform stress with cell parameters of series honeycomb structure is similar to that of single-layer honeycomb structure,which shows that the mechanical properties of multi-layer honeycomb structure are still determined by the mechanical properties of single-layer honeycomb.(2)According to the research results of series honeycomb structure,the parameters of regular hexagonal honeycomb structure are optimized,and the model of bridge plug rubber tube of series honeycomb structure is established.Using finite element simulation software,the static analysis of the traditional and honeycomb structure is carried out,and the sealing performance parameters K and shoulder value J are introduced to compare the sealing performance and shoulder stress concentration of the traditional and honeycomb structure under different setting loads.The results show that the sealing performance of series honeycomb structure bridge plug rubber cylinder is improved by 2%,and the stress concentration phenomenon at shoulder is obviously improved.(3)A model for calculating the dissolution time of bridge stopper with honeycomb skeleton in series structure was established,and experiments for measuring the dissolution rate of TPU rubber material in DFM solution were designed and carried out.The dissolution rates of TPU rubber material in DFM solution at different temperatures were obtained.According to the dissolution experiment of single-layer honeycomb bridge plug,the accuracy of the calculation model of dissolution time of rubber cylinder was verified.Combined with the three-dimensional model established by Solid Works,the dissolution time of rubber cartridge was calculated.The results show that the concentration of DMF solution has little effect on the swelling and dissolution of rubber,and the dissolution rate of rubber increases with the increase of temperature and contact area.The dissolution rate of rubber pellets under different working conditions is deduced,and the expressions of dissolution rate of rubber pellets with temperature,material density and contact area are obtained.The dissolution time of honeycomb skeleton series bridge stopper rubber cylinder is calculated to be about 68 hours,and the dissolution rate is nearly twice as high as that of traditional rubber cylinder.