Study On Sealing Performance Of Packing Element In Permanent Packer Under Complicated Conditions

With the continual development of oil and gas resources exploration and development,oil and gas wells under complex working conditions,such as high temperature and high pressure deep wells/ultra-deep wells,hydrogen sulfide-containing wells and high-hydrogen sulfide-containing wells,have been developed in China.In order to protect tubing and casing pipe,extend wellbore mining life or achieve selective zone production,avoid interlayer interference,and improve utilization of single well,permanent packer completion technology has become an important technology for the exploitation of oil and gas wells with high temperature,high pressure and high sulfur.Packing element is the key component of the permanent packer and its mechanical properties directly determine the setting effect and sealing performance of the permanent packer.For a systematical and deep study on the sealing performance of permanent packer under extreme conditions,the research methodology which combines theoretical analysis,finite element simulation and laboratory test have been adopted to study the mechanical behavior and sealing performance of the permanent packer under the coupling of temperature,pressure,medium and time.The main research work are as follows:(1)Constitutive Model Experiment Study on Hyperelasticity and Viscoelasticity of Rubber Material.The uniaxial tensile test,plane tensile test and equal biaxial tensile test of the rubber material were carried out on the basis of non-contact measurement method.According to thermodynamic statistical theory,a tube model was introduced to modify the eight-chain network model,thus obtaining a new hybrid hyperelastic constitutive model.And the reliability and applicability of the new hyperelastic constitutive model are verified by the above three constitutive experiments data.In addition,the stress relaxation experiments of rubber materials were carried out and the Prony series parameters of the generalized model were fitted based on the least squares method.(2)Experiment Study on Sealing Performance of Packing Element in Permanent Packer.Based on the VIC-3D non-contact full-field strain measurement system,a visual experiment bench for sealing performance study of packing element was designed and built.The deformation and sealing capacity of HNBR(hydrogenated nitrile rubber rubber)packing element with different hardness and different height under different axial loads were tested,which systematically revealed the deformation law of packing element in compression packer at different stages.Based on the finite element theory,a finite element simulation model for the bench experiments were established and the simulation were verified by the bench experiments.With the help of the bench experiment results and finite element simulation results,the evaluation criteria of sealing performance of packing element in compression packers has been established.(3)Study on the Hot Oil Aging on the Sealing Performance of Packing Element in Permanent Packer.Hot oil aging experiments of HNBR with two different hardnesses under 9 different aging time were conducted through the heat aging test chamber.Based on the uniaxial tensile test and stress relaxation test data,the influence of hot oil bath aging on the physical and mechanical properties of rubber materials was analyzed.The sealing performance of packing element in permanent packer under high temperature oil bath condition was analyzed by finite element simulation methodology on the basis of the new hybrid hyperelastic constitutive model and generalized Maxwell model.(4)Study on the Influence of High Temperature,High Pressure and High Sulfur Corrosion Environment on the Sealing Performance of Packing Element in Permanent Packer.The corrosion experiments of gaseous and liquid high temperature and high pressure hydrogen sulfide of tow HNBR samples with different hardness under 6 groups of different corrosion time were carried out through high temperature and high pressure reactor.The uniaxial tensile test and stress relaxation test were carried out to study the changes of mechanical properties of rubber materials under the gas phase and liquid phase hydrogen sulfide environment with high temperature and high pressure.Based on the hyperelasic and viscoelastic constitutive theory of rubber materials,the finite element model of packing element was established and its sealing performance in high temperature,high pressure and high sulfur environment was analyzed.(5)Multi-Objective Optimization Design of Sealing Performance of Packing Element in Permanent Packer.The factors affecting the sealing performance of packing element were systematically analyzed.The design variables and range of the packing element of permanent packer rubber were chosen on the basis of the orthogonal test method.The second-order polynomial regression equation of the rubber cylinder sealing performance was established based on the response surface methodology.Fruit fly optimization algorithm(FOA)optimized by Pareto non-dominated sorting was used to solve the multi-objective optimization of sealing performance of the packing element.The research results provide experimental support for material selection and optimization of the vulcanization process of packing element in permanent packer.In addition,the results lay a foundation for the research of failure mechanism and life prediction of permanent packer,and provide theoretical guidance and experimental support for the development of long-life,high-reliability packing element in permanent packer.Totally,the research has important theoretical value and practical significance for the development of permanent packer completion technology.