The Risk Based Approach Applied To Produced Water And Its Consequences For Both PW And Offshore Chemicals
Authors: Garland Emmanuel 
Published: May 2011

OSPAR, the regulatory body for the prevention of the pollution of the North East Atlantic (which includes the producing area of the North Sea has decided to move from a prescriptive approach on the quantity of oil in produced water discharged to the sea to a risk based approach to identify where to put impetus and money to reduce the environmental footprint of these discharges, if any.

The proposal combines a Whole Effluent Assessment (WEA), and a Predicted Environmental Concentration / Predicted No Effect Concentration (PEC/PNEC) approach on all and every substances identified in the produced water. As such it is a preservative measure, which has at first glance the advantage of being clear and consistent. But it has also weaknesses and pitfalls. Not only because the use of safety factors in the calculation of PNEC of substances in produced water is very conservative and may lead to erroneous conclusions and unnecessary changes in the process of some installations, but also because the overall benefit for the environment is not demonstrated. OSPAR has already implemented strict measures on produced water, and on the chemicals used and discharged offshore.

The effect of this latest measure taken on chemicals " which are candidate for substitution?? (i.e. the hazardous ones), which will be fully implemented by 2017, will undoubtedly dramatically reduce the discharge of hazardous chemicals used offshore, and the need for another measure, superimposed to the ones already taken by OSPAR, is questionable.

Introduction

The oil and gas upstream industry (Exploration & Production) produced roughly 423 million tons of oil equivalent of hydrocarbons in 2008 in the North Sea (Ref 1). As a by side product, it also produced and discharged 385 million cubic meters of produced water, and used in 2008 228,000 tons of chemicals (other than PLONOR chemicals, i.e. chemicals which have been acknowledged as Posing Little Or NO Risk to the environment) and it is estimated that 35,000 tons of these chemicals were discharged into the sea (Ref 2).

Since 1978, OSPAR, the regulatory body for the prevention of the pollution of the North East Atlantic (which includes the producing area of the North Sea), has taken measures to limit and reduce the quantity of contaminants discharged to the sea. The measures where strengthened several times since then. Meanwhile, many studies have been undertaken, in several parts of the world, which concluded to limited impact of the produced water discharged to the environment by oil and gas exploration and production activities. But what's limited really means? Does it mean a negligible impact, or does it relates to non-harmful discharges?

That's a question the scientific community has never managed to answer satisfactorily.

For all these reasons, OSPAR, which is committed to " take all possible steps to prevent and eliminate pollution from offshore sources?? (Ref 3), and in particular " to achieve by 2020 a reduction of oil in produced water discharged into the sea to a level which will adequately ensure that each of those discharges will present no harm to the marine environment?? (Ref 4, indent 20), and which appears to face difficulties to define an acceptable level of contaminants under which no harm to the environment is guaranteed, decided to change its approach and to move to a risk-based approach.

The measures taken so far

As mentioned above, the first measure was taken in 1978 by the Paris Commission, one of the ancestors of OSPAR. It laconically referred to a " provisional?? target standard of 40 mg/l for discharges from existing platforms. The measure was reinforced in 1986, when it became a formal OSPAR Recommendation. The measure remained valid fifteen years, until OSPAR Recommendation 2001/1 for the Management of Produced Water from Offshore Installations entered into force, in June 2001 (Ref 5).