芯轴式封隔器金属密封设计及密封性能分析

Metal Seal Design and Sealing Performance Analysis of Mandrel-Type Packer

针对油页岩、页岩油、重质油和富油煤等非常规油气资源采用地下原位改质技术开采,井下存在高温、高压和腐蚀环境,常规封隔器及其密封不能满足工程要求的问题,设计了一种芯轴式金属对金属密封的井下封隔器,密封副采用耐高温和腐蚀的Inconel 625材料,其中密封座采用金属陶瓷涂层结构。进行了封隔器坐封密封原理试验。试验结果表明,封隔器能在油套大环空间隙形成密封,且密封能力随着坐封载荷的增加而增大。基于密封接触能原理,应用ANSYS软件模拟了井下封隔器的密封性能,并对其影响因素进行研究。研究结果表明:涂层厚度和涂层弹性模量对密封能力影响不显著;芯轴密封面椭圆率和过盈量对密封能力影响较大,起决定性作用。基于密封副高温、持久载荷作用下许用应力低和密封能力评价指标,给出了密封结构参数设计方案,密封座涂层材料为Cr_(3)C_(2)-NiCr,涂层弹性模量250 GPa,涂层厚度为0.3 mm,椭圆率为,过盈量为0.02 mm。研究结果可为高温、高压、腐蚀环境下封隔器的开发和应用提供理论指导。

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 simulate 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 Cr_(3)C_(2)-NiCr,the elastic modulus of coating is 250 GPa,the coating thickness is 0.3 mm,the ellipticity is 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.