The issue of BOP reliability has long been discussed and despite important advances it continues to generate concerns among offshore safety regulators. As for any safety barrier, it is difficult to know its true operational status during process operation. The idea of devising means and methods to somehow monitor the condition of the BOP in real-time has been in on the agenda of operators, contractors and regulators for quite some time. In this paper, we introduce the main functions of a real-time decision support tool related to the subsea BOP retrieval decision during drilling. The main goal of this new tool is to contribute to better-informed decision-making regarding operational safety and reliability of BOPs, while its ultimate purpose is to reduce BOP downtime thus reducing drilling costs while maintaining its safety margin. The Tool incorporates both qualitative and quantitative methods to help guide the operator decision-making after detection of a BOP component or subsystem failure during drilling. Entirely new in this Tool is the use of quantitative probabilistic criteria, which makes it a fully quantitative risk-informed decision support system. The computational engine is based on an advanced time-dependent reliability analysis of each BOP safety function before (normal condition) and after one or more detected component or subsystem failures. Results for the case of a real BOP operating in the North Sea are presented and discussed in this paper.
Together with the downhole safety valve (DHSV), the Blowout Preventer (BOP) is considered to be one of the most critical of the safety systems involved in offshore oil exploration and production operations. Both such devices are active emergency flow blocking ones, but the much higher complexity of the BOP puts it in a special place not only in comparison with the DHSV but amongst the entire set of offshore safety devices. The recent Montara and Macondo (Refs. 1 and 2) accidents have made it entirely visible to the whole world the huge consequences that can result when the BOP fails to perform its assigned safety functions. In addition, recent studies (Refs. 3 and 4) have shown that BOP unreliability is still responsible for 40-50% of drilling downtime, representing a cause of major losses to drilling contractors and oil operators.
