6. The Occurrence of Hydrocarbon Leaks—Process Systems

Many different systems on offshore petroleum installations may cause leaks of hydrocarbon gas and/or liquid. Wells and well-related systems, systems for processing and treating of hydrocarbons, risers and flowlines and a few ‘utility’ systems most typically comprise the fuel gas system. This chapter is limited to hydrocarbon leaks or releases from all sources except wells and risers/flowlines. These systems are mainly processing and treatment systems, as well as the fuel gas system. Thus, the same scope here is that covered by the PSA in their Risk Level project under the ‘DFU1’ category. Trends are discussed for the UK as well as the Norwegian sectors and a comparison between these sectors is presented. The causes and circumstances of leaks are discussed in some depth, as are models for calculating leak frequencies. This includes the PLOFAM(2) hydrocarbon leak model. The chapter builds heavily on the work carried out for the PSA and Norwegian Oil and Gas.