Analysis of hydrocarbon leaks and verification as an operational barrier

Abstract

Prevention of hydrocarbon (HC) leaks is important; they are the most critical precursor events that may lead to major accidents, such as the Piper Alpha catastrophe in 1988. The number of HC leaks on offshore production installations on the Norwegian Continental Shelf peaked just after year 2000, with more than 40 leaks per year with initial rate above 0.1 kg/s. The Norwegian Oil and Gas Association carried out a reduction project from 2003 until 2007, which resulted in 10 HC leaks above 0.1 kg/s in 2007. The number of leaks increased in the years after 2007 and was on average 15 in the period 2008–2010, without any significant increase in the number of installations. A new initiative was launched early in 2011 in order to reduce the number of HC leaks further. A study performed by the project concludes that more than 50% of the leaks are associated with failure of operational barriers during manual intervention into the process systems. Human and organisational factors are dominating with respect to circumstances and root causes. The study has further demonstrated the high importance of verification as an operational barrier and has shown that many of the failures do not have multiple operational barriers in the form of several verifications and a leak test at the end. This finding is crucial in order to understand the criticality of performing the planned verifications, perform them in an independent manner according to the procedures and make sure that the focus is on detecting failures during the verification. This paper presents the analysis of HC leaks, with emphasis on operational barriers and importance of verification.