Risk assessment of anchor chain fracture in the mooring system of deepwater semi-submersible drilling platforms

As offshore oil and gas exploration moves towards deeper waters, deepwater semi-submersible drilling platforms are confronted with the dual challenges of outdated mooring systems and frequent extreme sea conditions. This paper takes a semi-submersible platform in the South China Sea as the research object, and uses coupled dynamics analysis methods, Weibull distribution extreme statistical models to conduct a systematic study on anchor chain fracture under extreme environmental loads. The research results show that by analyzing the platform drift and the minimum safety factor of the anchor chain tension under operating conditions, it can be observed that as the environmental incident angle increases, the dynamic response of the platform mooring system becomes stronger, and the risk of the mooring system breaking also increases. When the incident angle is 90°, the environmental load corresponding to the critical point of anchor chain fracture has a recurrence period of 1376 years. At this time, the safety factor of the windward anchor chain drops to 1.66, and the risk probability of anchor chain fracture is approximately 1.985×10-6 per year. Practical guidelines and solutions derived from current research results can be used for drilling platforms protection work to avoid safety accident problems caused by anchor chain fracture.