Analysis On Mechanical Behavior Of Definite Deformation About Packer Rubber

Currently,thin layer and small spacing technique of injection production process in the main oilfields of our country develops rapidly.As a key component of realizing the block and division of oil reservoir in oil water well,the rubber of packer affects the result of separate layer injection and production with various mechanical performance under different down-hole working conditions,which put forward a urgent demand for the research on the mechanical behavior with finite deformation and the applied technology of rubber.The home and aboard research status and history of rubber are summarized in detail for the holistic approach and main research direction of the dissertation.Based on the analysis of the hyperelastic theory for the packer rubber's mechanical behavior,the contact and frictional theory between rubber and casing and expounded the basic theory of sealing,the dynamic explicit solving expression and the specified criterion for the failure of sealing are proposed by employing the Finite Element Analysis(FEA)method in establishing the numerical model of packer rubber with various geometry,material and nonlinear contact location.The oil immersion test on the commonly used rubber(NBR-S,NBR-C,HNBR-S,HNBR-C)of packer with the high temperature and pressure reactor for large deformation is proceeded to achieve the stress-strain curves of four kind of oil-immersed rubber of,which may reveal the variation trendency of stress-strain relation with the temperature.Referring the Eight-chain model and the hyperelasticity of large-scale deformation range considering the advantage of Van der Waals model in expressing the shape of rubber's stress-strain curve,the Eight-chain model is revised correspondingly,by which the explicit formulation that fully considered all situation covered immersion,high temperature and large deformation is elicited as in M_AB constitutive model.The classical Treloar test data and practical test data from packer's rubber is fitted so that other deformation form can be predicated and the advantage of the revised Eight-chain model in explicit the downhole rubber mechanical behavior is verified.Aiming at the compression packer,the M_AB constitutive model is employed for mechanical behavior FEA with various working condition,different rubber and sleeve deformation offset,by which the covered frictional coefficient,axial load,working pressure,fluid temperature,rubber structure and casing deformation,while the stress covered frictional force,contact stress and Mises stress,are obtained systematically.With the specific experimental apparatus,the laboratory test on the frictional force and contact stress between rubber and casing under dry friction state and lubrication state is carried out.By the comparison of the test with the finite element analysis,the expressible ability of the correctional M_AB constitutive model and the reliability of the finite element analysis method are verified.The research could provide theoretical basis for the compression mode packer's rubber application under different working condition with broader range.It also could be viewed as the theoretical basis on the mechanical behavior of rubber-like material with large deformation.