Study on shearing capacity evaluation and promotion for blowout preventer ram in blowout scenario

Key words:  blowout preventer ram  complicated load  shearing force  blowout scenario  structural optimization

Abstract:

The analysis model was established to analyze the shearing force for the blowout preventer ram, based on the mechanical model on drilling bar and criterion of material failure. The simulation result has been compared with the experimental result, to verify the validity of the model. To explore the effect of blowout scenario on the shearing capacity, the variation laws on shearing forces of the drilling rod with different internal pressures, external pressures and axial loads were further investigated. By considering the off-center case of the drilling rod, and aiming to the problem that the conventional shearing zone of the ram cannot be fully covered, the structure on the shearing edge of the blowout preventer ram was optimized, and the shearing evaluation of the drilling rod at different eccentric positions was carried out. The results show that, the axial compressive load and internal pressure will significantly increase the required shearing force of the drilling rod. Therefore, to meet the demand of shearing capacity for the blowout preventer ram, it is necessary to choose the proper type of the blowout preventer ram, in ordr to increase its safety factor of shearing. The new designed shear ram can not only decrease the maximum shearing force, but also solve the problem that the drilling rod is at the off-center positions, which significantly promotes the shearing capacity of the blowout preventer ram.