Environment Report 2014

However, in 2013, the volume of drilling chemicals discharged increased by 35 per cent from 2012, while the total number of wells drilled remained relatively low at 164. Analysis of the top ten largest drilling discharges in 2013 showed that they are associated with multiple, rather than single, wells at the same site (a main well plus at least two sidetracks), increasing the overall length of wells drilled and hence the amount of chemicals used offshore. The majority of drilling discharges in 2013 are associated with mobile drilling units that were deployed to drill exploration and production wells in new and existing fields west of Shetland, in the southern North Sea and for subsea tiebacks in the central North Sea (CNS). Meanwhile, nine per cent of drilling fluids discharged came from existing fixed production platforms to develop current fields and for maintenance of well integrity. Small volumes were also discharged during well plug and abandonment (P&A) activities in the CNS and northern North Sea areas. Over the next decade, the proportion of drilling fluid discharges coming from well P&A may increase as activity in this area is forecast to rise. Over 900 wells are forecast to be decommissioned in this period 10 . 3.3.2 Chemical Discharge Composition On the UKCS, only chemicals that have been registered with the Centre for Environment Fisheries and Aquaculture Science’s (CEFAS) Offshore Chemical Notification Scheme (OCNS) are permitted. The OCNS applies the OSPAR Harmonised Mandatory Control Scheme (HMCS), developed through OSPAR Decision 2000/2 (as amended by OSPAR Decision 2005/1) and its supporting recommendations. The OSPAR HMCS contains a list of chemicals considered by OSPAR to pose little or no risk to the environment (PLONOR list). The OCNS involves generating an environmental dataset on toxicity, persistence and bioaccumulation potential using pre-screening criteria and a decision-support tool called CHARM (Chemical Hazard Assessment and Risk Management). Operators must consider the CEFAS OCNS classification as part of their risk assessment on the discharge of any chemicals as well as the European REACH (Registration, Evaluation, Authorisation and restriction of Chemicals) Enforcement Regulations 2008, which impose obligations on manufacturers/importers of substances and downstream users to evaluate and control the risks associated with their use.

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10 Oil & Gas UK’s Decommissioning Insight 2014 is available to download at www.oilandgasuk.co.uk/knowledgecentre/market_information.cfm

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