The quantification of energy consumption and gaseous emissions associated with decommissioning offshore oil and gas installations

Following the failure to implement the proposed deep-sea disposal of the North Sea Brent Spar oil installation the UK oil industry has identified energy consumption and gaseous emission as a key determinant of environmental impact associated with the abandonment of offshore facilities. In the absence of a standardized methodology this paper describes the approach adopted and results achieved using the North Sea Heather platform as a case study. The study develops and then applies a set of rules for conducting such analyses. Results show that in terms of energy consumption and greenhouse gas emissions there is little to choose between most partial and complete removal options. The energy cost advantages of recycling are largely offset by increased transport costs returning materials to shore. The study also highlights the importance of case specific variables, in particular, marine vessel fuel consumption.