Environment Report 2016

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ENVIRONMENT REPORT 2016
Produced Water Composition
Produced water accumulates small amounts of naturally occurring substances through contact with the reservoir
rock, including dispersed oil, dissolved organic compounds and naturally occurring radioactive materials (NORM).
Trace production chemicals are also present. If discharged with produced water, these chemicals rapidly dilute
within the marine environment. The type and composition of chemicals is determined by the reservoir geology,
maturity and production life stage.
Oil in Produced Water
In 2015, around 2,300 tonnes of oil were discharged with produced water, making up just over 0.001 per cent
of the total mass of produced water discharged – the same as in 2013 and 2014. OSPAR 14 Recommendation
2001/1 requires that individual installations do not exceed an average annual oil in water concentration of
30 milligrammes per litre (mg/l). In 2015, the average concentration across the industry was less than half, at
14.2 mg/l, measured using the GC-FID method15. This is a slight increase on 2014, but maintains the general trend
since data have been recorded using this method (see Figure 2 opposite).
At such low concentrations, the impact of the oil discharged in produced water on the marine environment is
considered to be very small as the fluids disperse rapidly and are greatly diluted in the North Sea. Small amounts
of oil are able to be quickly broken down by naturally occurring bacteria.
The IOGP reports that the global average oil content in produced water from offshore installations in 2014 was
12.8 mg/l. In Norway, the concentration of oil in produced water increased steadily from 2000 to 2014 then
dropped slightly last year to 12.3 mg/l. Norske Olje & Gass reports that a total of 1,819 tonnes of oil were
discharged with produced water on the Norwegian Continental Shelf in 2015. The 2014 UKCS average
concentration was 12.8 mg/l and despite the slight increase in 2015 remains largely comparable to both the global
and Norwegian values.
14 The OSPAR Commission aims to protect and conserve the North East Atlantic and its resources. See
15 Up to 2006, oil concentration in produced water was measured using the infrared method (IR). The IR method
measures, in solvent, both the dispersed and dissolved hydrocarbons extracted. This method can, however, include
other organic chemicals, giving an artificially high result and can also underestimate dissolved hydrocarbons. To rectify
this and to provide a more accurate analysis of hydrocarbon content, OSPAR agreed (Agreement 2005-15) the use of
a new method for oil in water analyses, based on a modified version of the ISO 9377-2 (GC-FID) method.