Metal Seal Design and Sealing Performance Analysis of Mandrel-Type Packer
When the underground in-situ upgrading technology is used to produce unconventional petroleum resources such as oil shale,shale oil,heavy oil and oil rich coal,the conventional packer and its sealing cannot meet engineering requirements due to downhole high-temperature,high-pressure and corrosive environments.Therefore,a metal to metal sealed plug-in structure downhole packer was designed,with sealing pair made of high-temperature and corrosion resistant Inconel 625 material,and sealing socket adopting metal-ceramic coating structure.Then,a sealing principle test of packer setting was conducted.The test results show that the packer can form a seal in the large annular clearance of tubing and casing,and the sealing ability increases with the increase of setting load.Moreover,based on the principle of sealing contact energy,the ANSYS software was used to simu-late the sealing performance of downhole packer and conduct study on its influencing factors.The study results show that the thickness and elastic modulus of the coating do not have obvious influence on the sealing ability,while the ellipticity and wring of the mandrel seal surface have a large influence on the sealing ability and play a decisive role.Finally,based on the situation of low allowable stress of sealing pair under high temperature and sustained load as well as sealing ability evaluation indicator,a seal structure parameter design scheme was proposed:the coating material of sealing socket is Cr3C2-NiCr,the elastic modulus of coating is 250 GPa,the coating thickness is 0.3 mm,the ellipticity is 1/30 and the wring is 0.02 mm.The study results provide theoretical guidance for the development and application of packers in high-temperature,high-pressure and corrosive environments.
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