Assessment of the possible effects of releases of oil and chemicals from any disturbance of cuttings piles (2009 update)

Abstract

From the Executive Summary: “The Disturbance of Cuttings Piles Raises Concern Cuttings piles arise from drilling operations where the drilled cuttings and associated drilling fluids are discharged at the location of the well. Old cuttings piles may contain organic-phase drilling fluids and have been identified as possible sources of hydrocarbon releases into the marine environment, due to remobilisation of residues of oil still found in the piles and natural leaching in to the water column. Concerns arose over the potential remobilisation of cuttings piles due to disturbance from other activities, i.e. trawlingand decommissioning activities.

Research Studies Have Investigated Possible Impacts on the Marine Environment The United Kingdom and Norway have carried out several research studies to assess the potential for impacts arising from the re-distribution of contaminated cuttings due to disturbance. OSPAR Recommendation 2006/5 on a Management Regime for Offshore Cuttings Piles aims at reducing to a level that is not significant, the impacts of pollution by oil and/or other substances from cuttings piles.

No Major Impacts on the Marine Environment Have Heen Detected A Norwegian study assessing the level of hydrocarbon loss due to dredging activities concluded that leaching from dredging (water phase hydrocarbons) and leaching from a pile left undisturbed are small compared to the potential loss due to particle bound hydrocarbon losses during a dredging operation. However, the authors warned that the estimates presented within the report must be treated with care and be regarded as indications only. A study undertaken in the United Kingdom using trawling operations to disturb a cuttings pile concluded that although contamination was spread, it was not in amounts or at rates likely to pose serious wider contamination or toxicological threats to the marine environment. The act of spreading will encourage, albeit at a slow rate, increased aeration of deposited material which will enable its further degradation by natural processes. Further studies undertaken in the United Kingdom looked at the possible impacts from the removal of contaminated cuttings piles using suction devices. They have indicated that the disturbance of cuttings piles by suction equipment results in relatively low secondary pollution with the oil generally remaining bound to the drill cuttings.

There is No Need to Develop Additional OSPAR Measures It can be concluded that no OSPAR measure on this subject should be developed at this time. However, OSPAR Contracting Parties should reassess the situation and possible impacts in the meeting cycle 2013/2014, in the light of the results of further post-decommissioning environmental surveys.