UKCS Contribution to Delivering Environmental Targets

Produced Water Trading Scheme

Water is produced in combination with the associated hydrocarbons from oil and gas reservoirs; this produced water is first cleaned to remove hydrocarbons then discharged to sea. Currently the maximum allowable discharge of oil in produced water is 40mg/l; however the industry averaged around 20mg/l in 2005. Independent research indicates that produced water’s contribution to the total volume of oil entering the North Sea is around 6%. In 2005 approximately 240 million tonnes of produced water were discharged to sea and the rate of water production continues to rise as reservoirs age.

Following recommendations by OSPAR in 2001, the DTI is introducing new regulations to:

1. Limit dispersed oil in discharges to sea to a monthly average of 30mg/l by the end of 2006.
2. Reduce total dispersed oil in produced water discharges by 15% below the quantities produced in 2000 by 2006.

The reduction in the discharge of produced water effectively requires a 28% reduction in total water discharged to sea, given the continuing trend of increasing water production since the 2001 recommendation was made. It is also proposed that all new installations achieve zero discharges of oil in produced water to sea. This may be problematic to implement and will act as an impediment on new developments given most are subsea tiebacks and rely on the use of existing processing facilities. It is also questionable whether a zero discharge has an environmental benefit.

The Offshore Petroleum Activities (Oil Pollution Prevention and Control) Regulations 2005 (OPPC) came into effect on 20 August 2005 replacing POPA. Under OPPC, installations are granted a permit for activities discharging oil to sea. From 1 January 2006 the oil in produced water must not exceed 30 milligrams per litre as a monthly / yearly flow weighted average. Additionally, in 2006, each installation has a total tonnes of oil discharged to sea contained within their permit which operators should make every effort to comply with. The regulations include a trading mechanism through which installations should be able to work together to meet the UK wide target. The regulations also contain a substantial civil penalty, currently set at £108 for every kilo of oil discharged in excess of that permitted.

Recent improvements in produced water management have been maintained. The improvements in this area are an achievement for the offshore oil industry as the amount of water produced with oil increases as fields mature. This highlights the considerable efforts being made by both Government and industry in minimising the oil in produced water discharges. Each installation's produced water discharge is different and as such there is no single solution to reducing the oil discharges.

Current indications are that the industry will invest over £250 million in additional abatement measures to meet the new regulations. A large variety of techniques are already employed to remove oil from produced water and it has to be recognised that further abatement measures come with an environmental as well as a financial cost. These costs should be compared with the incremental environmental benefit. The Policy Studies Institute⁵ has examined the overall environmental impact from further abatement of produced water and made an overall impact assessment. The study concludes that current levels of emissions suggest only a hypothetical or low risk; it must be questioned, therefore, whether the substantial new investments will deliver environmental value for money and provide the most appropriate environmental effects.

⁵ Management of Produced Water on Offshore installations: A Comparative Assessment Using Flow Analysis published Mar. 2005 (Ekins, Vanner and Firebrace)Back