An Estimate of the Cumulative Environmental Effects of the Disposal in the Deep Sea of Bulky Wastes from the Offshore Oil and Gas Industry

An Estimate of the Cumulative Environmental Effects of the Disposal in the Deep Sea of Bulky Wastes from the Offshore Oil and Gas Industry Gordon Picken; Gordon Picken CORDAH Environmental Management Consultants Search for other works by this author on: This Site Google Scholar Tim Curtis; Tim Curtis CORDAH Environmental Management Consultants Search for other works by this author on: This Site Google Scholar Alan Elliott Alan Elliott University of Wales Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Offshore Europe, Aberdeen, United Kingdom, September 1997. Paper Number: SPE-38510-MS https: //doi. org/10. 2118/38510-MS Published: September 09 1997 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Picken, Gordon, Curtis, Tim, and Alan Elliott. "An Estimate of the Cumulative Environmental Effects of the Disposal in the Deep Sea of Bulky Wastes from the Offshore Oil and Gas Industry. " Paper presented at the SPE Offshore Europe, Aberdeen, United Kingdom, September 1997. doi: https: //doi. org/10. 2118/38510-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE) SPE Offshore Europe Conference and Exhibition Search Advanced Search AbstractThis paper presents an assessment of the potential cumulative environmental effects of the deposition at the North Feni deep sea disposal site of 24 of the steel platforms presently located on the UKCS. It is argued that justification for deep sea disposal could only be made if it were possible to demonstrate significant benefits in terms of reduced risks to persons during the decommissioning process. If large steel jackets could be toppled and transported in the water in one piece, and then released at the deep sea site, this would, it is suggested, reduce the risk to personnel who would otherwise be engaged in underwater dismantling and lifting operations. Candidate structures were therefore identified as those that weigh more than 10, 000te in air (the maximum single lift capacity of present heavy lift vessels), and stand in water more than 100m deep (thus permitting toppling of the whole structure under present IMO guidelines). If these structures were deposited at North Feni over a period of about 24 years, the main potential source of cumulative effects would be from the release of contaminants as the sacrificial aluminium anodes were depleted. It is estimated that some 10, 700te of anodes would be deposited, giving rise to a peak daily wastage rate of 1, 400kg. A modified advection/diffusion model was used to predict the possible dispersion of the dissolved contaminants away from the site of deposition on the seabed. It was concluded that the peak concentrations of all contaminants in the water column extending from 0m to 20m above the seabed would be very low, and would not exceed the coastal Environmental Quality Standard (EQS). Concentrations in the water column from 20m to 40m above the seabed would be an order of magnitude less than those found near the seabed. IntroductionThe disposal of the inert bulky remains from oil and gas structures in the deep sea is permitted under existing international legislation, provided that the proposed disposal site is selected after proper consideration of the potential impacts on the environment and natural resources, and provided that the requirements of the IMO guidelines on consultation are met (Ref. 1). The IMO recommend that any deep sea disposal site should be at least 150 miles from the nearest land, and in water not less than 2, 000m deep. No previous study has attempted to describe and quantify the cumulative effect of a long-term deep sea disposal programme, and this lack of information was highlighted in the Natural Environment Research Council Report on decommissioning (Ref. 2). This paper defines a set of criteria with which candidate jackets for deep sea disposal may be identified, calculates the theoretical burden of contaminants that may be introduced, and models the likely concentrations of dissolved contaminants from the material that may accumulate there. The possible effects of these elevated concentrations are then assessed. Selection of Structures that may be Deposited in the Deep SeaDisposal scenario and selection criteriaThere has hitherto been no assessment to establish which existing structures might be potential candidates for deep sea disposal. With the exception of Brent Spar, no structure has yet been proposed as a candidate for deep sea disposal. The following selection process was used in this hypothetical study to select candidate structures, using published data. No operators were contacted about their decommissioning intentions. No detailed engineering studies of the proposed disposal method have been undertaken. P. 349^ Keywords: deep sea, Upstream Oil & Gas, cumulative environmental effect, Disposal, bulky waste Subjects: Environment This content is only available via PDF. 1997. Society of Petroleum Engineers You can access this article if you purchase or spend a download.