Brent Spar - Technical Information

Technical Information

Brent "E" was a floating oil storage facility constructed in 1976 and moored approximately 2 km from the Brent "A" oil rig. It was jointly owned by Shell and Esso, and operated wholly by Shell, which gave them responsibility for decommissioning the structure. The Brent Spar was 147 m high and 29 m in diameter, and displaced 66,000 tonnes. The draft of the platform was such that manoeuvring in the North Sea south of Orkney was not possible. The storage tank section had a capacity of 50,000 tonnes (300,000 barrels) of crude oil. This section was built from 20 mm thick steel plate, reinforced by ribs and cross-braces. It was known that this section had been stressed and damaged on installation. This led to doubts on whether the facility would retain its structural integrity if it was refloated into a horizontal position.

Throughout the decommissioning process, Shell based its decisions on estimates of the quantities of various pollutants, including PCBs, crude oil, heavy metals and scale, which it had calculated based on the operating activities of the platform, and the quantity of metal that would remain in the structure after decommissioning was completed. Scale is a by-product of oil production, and because of the radioactivity found in the rocks from which the oil is extracted, is considered to be low-level radioactive waste. It is dealt with on-shore on a regular basis, by workers wearing breathing masks to prevent inhalation of dust.