Sealing performance analysis of rubber core of annular BOP: FEM simulation and optimization to prevent the SBZ

The present work studies the influence of oil pipe joint passing through annular blowout preventer (BOP) on its sealing performance in high pressure gas wells under snubbing service. When the oil pipe joint passes through the BOP, due to the change of its structure, it is easy to cause the rubber core seal failure of the BOP, resulting in the leakage of toxic and harmful gas in the well, which seriously threatens the safety of the operators. Aiming at the problem of gas leakage caused by rubber core seal failure of annular BOP, based on the rubber large deformation theory and rubber core seal mechanism, a dynamic finite element model of rubber core-oil pipe joint is established, and the correctness of the model is verified by comparing the failure of rubber core on site; The results show that when the oil pipe joint passes through the BOP, a sealing buffer zone (SBZ) will be formed at the upper and lower shoulder of the joint, and the contact stress of the rubber core will decrease by 10 MPa–30 MPa; Because of the funnel effect of the rubber core, the damage of the rubber core caused by the running oil pipe joint of the BOP is greater than that caused by the lift oil pipe joint; When lifting oil pipe, the existence of SBZ is easy to cause gas leakage in the well; The optimized structure of oil pipe joint with small inclination and long shoulder can significantly reduce the influence of SBZ on the sealing performance of BOP. The research work in this paper is of great significance to improve the dynamic sealing performance of BOP.