Environment Report 2015

Mass of Chemicals Discharged In 2014, just over 105,500 tonnes of chemicals were discharged to the marine environment (approximately 194 tonnes per million boe produced), of which almost 73 per cent (76,500 tonnes) was from drilling activities. The total amount of chemicals discharged has varied each year since 2000 (see Figure 5 overleaf) and is consistently dominated by the amount of drilling chemicals discharged. The 2014 total, however, was 20 per cent lower than the previous year. All discharged chemicals dilute to levels that are not acutely toxic to marine organisms, reaching dilution of at least 1,000 times at a distance of 500 metres from the point of discharge. Those chemicals that are not used or discharged are returned to shore for reuse or disposal through various waste processing routes. Specialist chemicals are used to produce oil and gas to maintain equipment integrity and optimise production. These chemicals include demulsifiers to improve oil separation from water; corrosion inhibitors to protect equipment; scale inhibitors to slow down scale build-up in pipework and valves; and biocides to reduce marine growth on equipment. There is a net increase of just over 300 tonnes in the amount of production chemicals discharged between 2000 and 2014, despite decreasing production levels. This highlights the increasing complexity of production in a mature basin. Pipeline chemicals are used for pipeline maintenance and include biocides and oxygen scavengers. Figure 7 overleaf shows that four times as many pipeline chemicals were used in 2014 than in 2013. The largest ten pipeline chemical discharges were from eight pipelines, all of which were either new or underwent major repair works in 2014 19 . All of these ten discharges, as well as 86 per cent of the total pipeline chemicals discharged, were PLONOR. Drilling fluids aremostlymade up of water, but also contain a range of chemicals to ensurewells can be drilled safely. Drilling fluids can increase the safety of operations by lubricating drilling equipment components, controlling well pressure and enabling drill cuttings to be removed. Cement and cement additives are also used in constructing wells. Figure 6 overleaf shows that, in 2014, just under four times more drilling fluids were used than discharged, reflecting the reuse of the fluids during drilling.

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19 These data are from the UK Oil and Gas Data website. See www.ukoilandgasdata.com

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