Optimization design for downhole dynamic seal based on response surface method

The downhole temperature and drilling fluid pressure have a significant influence on the contact pressure and leakage rate of the dynamic seal. This article attempts to improve the seal performance using response surface method and multi-objective optimization. The width of the sealing interface, the pressure difference, the hardness of the O-ring and the hardness of the support ring are defined as independent variables, while the outer contact pressure and the leakage rate of the seal are chosen as objective functions. The response surface method has been employed to construct mathematical models combining both the independent variables and the objective functions, and the accuracy of the mathematical models has been proved. Furthermore, the leakage rate was regarded as a constraint function; hence, the minimum outer contact pressure and corresponding design parameters were obtained. The outer contact pressure of the seal increases with the increase in the drilling pressure difference, but decreases with the width of the sealing interface; the relationships between the leakage rate and the independent variables have also been obtained. According to the multi-objective optimization, the leakage rate of the improved seal decreased by more than 10% compared to the previous seal.