Dynamic calculation of stress influence law of rubber core sealing surface of the rotating blowout preventer with defects

Abstract

The bubble and crack defects in the production and operation of the rubber core of the rotating blowout preventer (RBOP) easily cause fatigue failure, leading to well-controlled severe accidents. Based on Yeoh’s principal structure equation, the dynamic sealing model of rubber core was established in this paper. The sealing process of the rubber core in lifting and drilling was calculated and analyzed. The stress influence law of typical cracks and bubble defects that affect the fatigue failure of rubber core sealing surface was analyzed. The results are as follows: (1) When the drill pipe joint passes through the RBOP, the structure of the rubber core is significantly deformed. This stage may cause damage and failure of the rubber core. (2) The cracks and bubble defects lead to a decrease in the stability of the sealing surface. With the increase of stress at the defect, the crack of the rubber core is easy to expand. (3) In the same location of the rubber core defects, cracks compared to bubble defects have a more significant impact. For the same type of crack, the bottom left side (A₁) and the outer surface underside (D₁) crack reduce the stress at the position of the rubber core sealing surface to the maximum. The research results provide a reference basis for defect detection, sealing performance, and service life of rubber cores, in order to improve the reliability evaluation standards of blowout preventer rubber cores, improve well control safety, reduce the occurrence of safety accidents, and improve operational efficiency.