Study on the Shearing Force of Ram and Fracture Characteristics of Drillpipe Under Precutting

Abstract

The working pressure of the hydraulic system, as well as the volume and weight of the ram blowout preventer (BOP), cannot be increased excessively. This limitation affects the shearing force provided by the hydraulic cylinder of the BOP. When shearing high-strength, large-thickness, and large-diameter drillpipes, it is easy to cause shear failure, making blowout control challenging. Therefore, we proposed a high-pressure water-jet-assisted precutting method to reduce the force required to shear the drillpipe. Based on the numerical model verified by experiments, we compared and analyzed the shearing force variations and drillpipe fracture characteristics under different precutting methods. We also provided recommendations for selecting precutting methods. Furthermore, we identified the weights and grades of drillpipes that affect the shearing force under precutting. The results demonstrate that precutting the drillpipe can reduce shear forces, shorten fracture time, and improve fracture quality. The use of water-jet precutting technology enhances the efficiency of emergency well shut-in operations and subsequent pipe fishing. The presented technology is currently at a prefeasibility stage, and further efforts are needed to implement these ideas in practice.