非API套管接头主密封结构气密性能试验分析

非API套管接头主要通过金属对金属的径向过盈主密封结构，保证气井开采时的井筒内气密性。依据7 in．套管接头尺寸选用锥面对锥面径向主密封结构型式加工试件，通过密封面过盈配合尺寸控制密封预紧力，测试不同密封预紧力下的气体泄漏率；分别采用车削、磨削和研磨工艺加工接触面，对比分析不同表面粗糙度对气密性能影响程度；取径向密封接触宽度范围2．5～25 mm，测试相同密封预紧力和气体压力下，不同接触宽度对应的气体泄漏率。试验测试结果表明，较高的初始接触压力是形成金属对金属密封的必要条件，当接触压力接近2倍材料屈服强度后，随气体压力升高泄漏率曲线近似保持水平，径向金属密封产生稳定气密性能；密封面的表面粗糙度不同，其进入稳定密封状态的快慢程度不同，表面光洁度越高、进入速度越快气密性能越好；径向接触宽度在2．5～10 mm范围内，气体泄漏率随接触宽度增加而显著降低，10 mm以后接触宽度对气密性能影响不大。

Analysis of Gas Sealing Performance Test for Non-API Casing Connection with Radial Cone Sealing Structure

The metal-to -metal radial interference fit construction is the main sealing structure of the non-API casing connection.The sealing performance of the non-API casing connection is guaranteed by the special sealing structure.The main processing parameters of the test specimen are like the 7 inch casing connection.The main structure type is the cone to cone interference fit between two contact inter-faces.The leakage rate was measured in the test under different contact pressure controlling by the sealing surface interference.In order to analyze the sealing performance influencing by the surface roughness,the sealing contact surfaces are processed with turning,grinding and lapping.The leakage rate was measured under different contact width （2.5 -25 mm）in the same contact and gas pressure.The test results show that the higher initial contact pressure is necessary to air seal.The contact interface has occurred plastic deformation when the contact pressure close to 2 times metal yield strength.In this condition,the leakage rate is unchanged with the increasing of gas pressure,and then the gas sealing performance is in a stable state.The higher surface roughness come into stable sealing state much more quickly and easily comparing to the lower by comparing the gas sealing performance of the different surface roughness.The leakage rate decrease dramatically with the increasing of the contact width （in the range 2.5 -10 mm）,and the effect on the sealing performance comes very small when the contact width more than 10 mm.