Assessment of the discharges, spills and emissions from offshore installations on the United Kingdom Continental Shelf in 2012-2016
This report presents the discharge, spill and emission data for UK offshore oil and gas operations during the period 2012 – 2016 and provides an assessment of that data. The annual data on which the assessment is based is provided in Appendix 2.
Level of Activity
The United Kingdom Continental Shelf (UKCS) is a mature oil and gas province within the OSPAR region which has been experiencing declining production for many years, though there has been a significant increase over 2015 and 2016 due to start‐up of significant new developments (Figure 1). Oil and gas activity to maintain production levels and maximise economic recovery of reserves remains high including a notable upturn in the number of wells drilled (Figure 3).
The total hydrocarbon production from the UKCS decreased by 9,5% during the period 2012 – 2014, but subsequently increased by 31% from 2014 to 2016. There has been a small decline in the total number of surface installations but a 9% increase in the number of subsea installations reflecting the ongoing trend in developing smaller fields tied back to existing hub installations (Figure 2).
Discharges & Spills of Oil
The total quantity of dispersed1 oil (aliphatic oil) discharged to the sea from produced water and displacement water decreased during the assessment period, from 2 267 tonnes in 2012 to 2 017 tonnes in 2016, a decrease of 11% (Figure 5).
As in previous years, produced water and displacement water are the main contributors to the oil discharges from offshore oil and gas activities, representing 97‐98% of the total amount of oil discharged to the sea during the period 2012 ‐ 2016. Flare drop‐out is a minor source of oil discharge and is not covered by OSPAR measures, though it is reported in the UK as a spill should it occur.
It should be noted that dispersed oil in displacement water contributes less than 4% of the total dispersed oil discharged.
The annual average dispersed oil content in produced water has remained relatively stable over the period between 12,8mg/l to 14,6mg/l; well below the current performance standard for dispersed oil of 30 mg/l for produced water discharged into the sea (Figure 5).
Despite efforts made to reduce the number of installations which exceed the standard, there are still 11 installations that currently do not meet the standard; however, the amount of oil discharged from 8 of these installations is less than 2 tonnes annually in each case. In total the discharge of dispersed oil in excess of the 30mg/l performance standard is 0,3% of the total discharge of dispersed oil in 2016 for the UKCS (Figure 6).
Spills of oil to sea have varied over the period as might be expected ranging from 26 tonnes to 128 tonnes. There is no apparent trend in the data (Figure 7).
The use and discharge of chemicals have been regulated by OSPAR and UK national legislation since 2001, with the first national reports provided for 2003. The total quantity of chemicals used offshore decreased during the period 2012 – 2016 (Figure 9). On average, during the period 2012‐2016 less than 2% (by weight) of the total amount of chemicals used contains either substances on the OSPAR List of Chemicals for Priority Action (LCPA) or substances which are candidates for substitution.
The total quantity of chemicals discharged into the sea during the period 2012 – 2016 decreased from 68 019 tonnes to 59 306 tonnes and, on average 82% (by weight) of the chemicals discharged are on the OSPAR PLONOR list2.
OSPAR Recommendation 2005/2 set environmental goals for the reduction of discharges of LCPA substances, and discharges were to be phased out by 2010. This was achieved in the UK by 2012 and continued through until 2016 when there was a 3,4kg discharge of lead‐based pipe dope which was mistakenly permitted during drilling operations with a water‐based mud (Figure 10).
OSPAR Recommendation 2006/3 set environmental goals on the phasing out of discharges of chemicals that are, or which contain, substances identified as candidates for substitution3 by 2017. The quantity of substances identified as candidates for substitution discharged during the period 2012‐2016 appears to have levelled off with no obvious trends and with some small variations in quantity discharged between years.
While the reductions in the amounts of LCPA and substitution chemicals discharged since the OSPAR measures came into force are indicative of the success of the relevant OSPAR measures, recent increases are a matter for the UK to consider further.
Atmospheric emissions from offshore oil and gas activities are not regulated by OSPAR measures, but are reported annually by operators. Emissions to the atmosphere have generally decreased or remained stable with the exception of NOx which has increased over the period as a result of increased diesel use for power generation due to decreasing fuel gas availability (Figure 14 and Figure 15).
1. “Aliphatics” and “aromatics” are defined by the reference method set in OSPAR Agreement 1997-16 (Solvent extraction, Infra-Red measurement at 3 wavelengths). In that context, “aliphatics” and “dispersed oil” mean the same thing.
2 Pose little or no risk to the environment - PLONOR
3 Except for those chemicals where, despite considerable efforts, it can be demonstrated that this is not feasible due to technical or safety reasons. Demonstration of those reasons should include a description of the efforts.