Emergency Plugging Test System and Experiment for Blowout Preventer Seal Failure under Ultrahigh-Pressure and Large Displacement Conditions

Summary At present, there is still a lack of safe and efficient emergency rescue measures for blowout accidents caused by blowout preventer (BOP) seal failure. Although there have been previous proposals for emergency plugging of failed BOP by pumping materials, the method has been limited to the theoretical simulation stage and has not yet been fully validated experimentally. In view of this, we independently designed and constructed a set of large-scale plugging test systems for BOP, aiming to simulate the actual scene of BOP sealing failure under blowout condition and then implement the emergency plugging experiments. Through emergency plugging experiments and pressure cycle experiments, a suitable plugging formulation was screened, and it was verified that the material’s pressure-bearing strength and pressure-bearing time met the engineering requirements. Then, the effects of the yield strength of the plugging particles and the ratio of the gap width to the thickness of the material on the plugging efficiency were analyzed. The results show that the plugging material can migrate to the leakage port and achieve effective plugging under the high-pressure fluid. Formulation 6, using Φ10 mm × 10 mm and Φ8 mm × 8 mm polyether-ether-ketone (PEEK) as the bridging material, was capable of stable pressure-bearing for 10 minutes at a pressure of 70 MPa and was able to sustain pressure-bearing for at least 30 minutes at a pressure of 30 MPa or more. Increasing the yield strength of the bridging particle material as well as optimizing the ratio of granular thickness to gap width both contribute to the success rate of bridging plugging. This study further confirms the feasibility of emergency plugging measures and provides new technical means and strong support for well control and safety.