The high hazard mechanical system (HHMS) has three characteristics in the petroleum and petrochemical industry (PPI): high risk, high cost, and high technology requirements. For a HHMS, part, component, and subsystem failures will result in varying degrees and various types of risk consequences, including unexpected downtime, production losses, economic costs, safety accidents, and environmental pollution. Thus, obtaining the quantitative risk level and distribution in a HHMS to control major risk accidents and ensure safe production is of vital importance. However, the structure of the HHMS is more complex than some other systems, making the quantitative risk analysis process more difficult. Additionally, a variety of uncertain risk data hinder the realization of quantitative risk analysis. A few quantitative risk analysis techniques and studies for HHMS exist, especially in the PPI. Therefore, a study on the quantitative risk analysis method for HHMS was completed to obtain the risk level and distribution of high-risk objects. Firstly, Fuzzy Set Theory (FST) was applied to address the uncertain risk data for the occurrence probability (OP) and consequence severity (CS) in the risk analysis process. Secondly, a fuzzy fault tree analysis (FFTA) and a fuzzy event tree analysis (FETA) were used to achieve quantitative risk analysis and calculation. Thirdly, a fuzzy bow-tie model (FBTM) was established to obtain a quantitative risk assessment result according to the analysis results of the FFTA and FETA. Finally, the feasibility and practicability of the method were verified with a case study on the quantitative risk analysis of one reciprocating pump system (RPS). The quantitative risk analysis method for HHMS can provide more accurate and scientific data support for the development of Asset Integrity Management (AIM) systems in the PPI.

Summary: The blowout preventer (BOP) stack is the last line of defense for well control (pressure control of the wellbore), and the failure of its sealing components will cause serious well control accidents. At present, there is a lack of suitable experimental device to verify the feasibility of the emergency rescue method proposed for the early seal failure of the BOP stack by pumping plugging particles. However, it is costly, risky, and time-consuming to build and implement a large-scale plugging experimental model for BOP stack with ultrahigh pressure (70 MPa) and large displacement. Therefore, based on this device, this paper establishes a large-scale plugging experimental model of BOP stack by using computational fluid dynamics-discrete element method (CFD-DEM). The volume flow rate is used as the evaluation index to analyze the influence of the shape, size, concentration, and pump displacement of the plugging particle on the plugging efficiency, and the plugging parameters of the experimental device are researched and selected. The results show that the plugging particles can be divided into four stages—particle pumping, particle diffusion, particle bridging, and particle accumulation. The 5-mm spherical particle has the best plugging efficiency for the largest dimension of flange connection seal failure. The particle concentration and pump displacement affect the bridging time of particles but have no obvious effect on the plugging efficiency. A pump displacement of 2.4 m3/min and 5-mm spherical particles with 25% concentration were selected for emergency plugging of the experimental device. This study not only reduces the cost and risk of large-scale plugging experimental device for BOP stack but also further promotes the feasibility study of emergency rescue of BOP seal failure.

Blowout preventers (BOPs) are critical for ensuring operational safety in oil and gas development. Seal failure can lead to catastrophic accidents, such as uncontrolled blowouts. In engineering applications, the injection of bridging particles has been proposed as a temporary solution to plug leak points, providing a crucial time window for emergency response. However, the existing plugging mechanism remains poorly understood, limiting the advancement of plugging techniques. To address this issue, a numerical model for BOP hole-type seal failure was developed in this study using computational fluid dynamics (CFD) and discrete element method (DEM) simulations. Fluid–structure coupling analysis was conducted to clarify the particle bridging and plugging process. The influence of key parameters—including wellhead pressure, particle shape, particle size, pumping displacement, and particle concentration—on the plugging effect was comprehensively investigated. The results indicate that under 10 MPa and 40 MPa conditions, rectangular or cylindrical particles are preferred to enhance the plugging success rate and stability. At 10 MPa, the pumping displacement should be less than 1.5 m³/min, and the particle concentration should exceed 8%. At 40 MPa, the pumping displacement should exceed 2.0 m³/min, and the particle concentration should be greater than 6%. For higher pressures (70 MPa), particles larger than the leak point size are recommended, with a pumping displacement exceeding 2.0 m³/min and a particle concentration greater than 8%. This study provides practical recommendations for pumping displacement and particle selection under blowout conditions, significantly improving the success rate and efficiency of plugging operations. It also serves as a valuable reference for the development of plugging processes and technologies for BOP seal failure.

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.