单金属密封的结构优化及其密封性能研究

针对油气田勘探中，复杂的钻井工况导致动密封工作性能极不稳定的问题，结合单金属密封结构和井底高压环境，利用有限元方法对单金属密封受压情况下的接触压力进行分析。用雷诺方程计算单金属动密封的泄漏率，以减小最大接触压力和泄漏率为优化目标，利用正交试验和F评价方法对单金属密封结构参数进行优化，得到密封结构参数对密封面接触压力和泄漏率的影响情况，并将每个水平数对应的优化目标计算结果分别取平均值，得到不同水平影响下接触压力和泄露率平均值的变化趋势，从而确定密封结构的最优水平值，并借助有限元仿真对优化前后的密封性能进行对比。最后根据优化前后的密封结构参数加工2套密封试件，进行密封实验。仿真分析和实验结果表明：高压工况下优化前的密封面内侧磨损严重，钻井液颗粒容易侵入密封面；而优化后密封面的最大接触压力有所降低，动密封面的最高温度和泄漏率明显降低。研究结果对改进单金属密封的工作性能、提高井下动密封的可靠性有重要的现实意义。

Research on structure optimization and seal performance of single metal seal

In the exploration of oil and gas field, for the instability of the dynamic seal performance because of the complex drilling conditions, the finite element method was used to analyze the contact pressure of single metal seal under the working condition which combined with single metal sealing structure and high pressure environment. Then the leakage rate of the single metal seal was calculated by Reynolds equation. On this basis, the optimization of the dynamic seal was completed by orthogonal experiment and F evaluation method with the objective to reduce maximum contact pressure and leakage rate. Finally, the influence of the structure parameters of single metal seal on the contact pressure and leakage rate of the sealing surface was obtained, and the average values of the calculated results of the optimized target corresponding to the same number of levels were calculated. According to the calculated results, the variation trend of the average value for the contact pressure and the leakage rate were obtained to identify the optimal level of seal structure under different levels. The performance of the dynamic seal before and after the optimization was compared using the finite element simulation. According to the seal parameters, two sets of seal specimens were processed, and sealing experiment was carried out. Simulation and experimental results verified that the inner side of the seal surface was worn seriously under high pressure condition, and the drilling fluid particles were easy to invade the sealing surface, also the maximum contact pressure was decreased after optimization. Meanwhile, the maximum temperature and leakage rate of the seal were significantly reduced. The research has important practical significance to improve the performance of the single metal seal and the reliability of the down-hole dynamic seal.