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Muddied Waters

A Survey of Offshore Oilfield Drilling Wastes and Disposal Techniques to Reduce the Ecological Impact of Sea Dumping

by Jonathan Wills, M.A., Ph.D., M.Inst.Pet., for Ekologicheskaya Vahkta Sakhalina (Sakhalin Environment Watch); 25th May 2000

The Law on Offshore Wastes Discharges in Different Jurisdictions

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United Kingdom Law on Offshore Wastes Discharges (continued)

The guidance for licence applicants in the UK sector is extremely specific:

The environmental impact of the project should be a consideration from its inception and this should be evident from the Environmental Statement. However, the Statement should not be compiled until there is sufficient project engineering detail to enable the environmental impact of the project to be assessed and potential significant impacts to be identified. Where appropriate, variations in performance of specific processes, etc. (e.g. due to differences in supplier specifications) should be covered by providing an envelope of performance within which the project will operate.

The description of the project should be sufficiently detailed to enable the reader to understand its essentials and the source of any discharges to the environment or other environmental impacts. Where the project is a field development, the description should encompass all its elements, such as platforms, production vessels, sub-sea structures, the means of hydrocarbon transportation and intrafield pipelines, and the envelope of fluid processing, production and emission rates. Where it is envisaged that the project may expand with time, the full extent should be considered where known.

The data provided to identify and assess any significant effects which the project is likely to have on the environment should be presented as interpreted (rather than raw) data with sources referenced.

Care must be taken to ensure the information is up-to-date and relevant to the geographic area of the project.

The discussion of the likely significant effects should be accompanied by an indication of the criteria by which "likely" and "significant" are categorised. It is expected that these criteria will normally consider the significance of an impact under a number of headings including: extent and magnitude; duration; reversibility; sensitivity of the receptor; species rarity, etc.; and compatibility with standards and policy.

Detailed quantification of adverse effects should be made and include, where possible, estimates of the costs resulting from them.

Where a project is liable to give rise to effects which of themselves are not significant but which, when compounded with existing or expected effects from other sources, will have a significant adverse effect, then these should be described.

The opportunity should be taken to mitigate (i.e. avoid, reduce or remedy) adverse environmental effects in the design and operation of the project. The Environmental Statement should identify where and how this will be done. The performance parameters of processes and procedures adopted, such as separation of water from oil, should be described.

Many of the potential significant adverse effects will have been eliminated or reduced by the processes and procedures adopted and these will have been described as explained above. Consent may be refused in cases where the project does not make provision for a comprehensive externally verifiable Environmental Management System to be established for the lifetime of the project and for a mechanism for its periodic review in the light of experience and technological advances. Where such a system is intended its essentials should be described in the Environmental Statement and include provision for monitoring the actual impact of the project on the environment and for auditing of the System's effectiveness.

The Statement should also address the risk and potential impact of failure, accident or malfunction of the procedures and processes (including those related to the reservoir), the precautions to be taken and how these will be incorporated into the project's Environmental Management System.

The non-technical summary should aim to provide an informed lay reader with an accurate account of the development and its impact on the environment. It is recommended that this should precede the more technical sections of the Environmental Statement.

Where significant adverse environmental impacts are identified, a more detailed explanation should be given where any alternatives which might have mitigated or avoided these impacts are not being adopted.

Any cumulative effects of the proposed development should be addressed, both quantitatively and qualitatively. Where there are gaps in data or understanding of environmental processes these should be explained and provision made to fill and act on these, usually in an Environmental Management System.

It is desirable that the Environmental Statement should incorporate the Licensees' stated environmental policy.

Table 3: Trigger Tonnages

Type of chemicals Group* Trigger tonnage**
(above which government must approve use)
Production (including stimulation and injection chemicals) A 40 tonnes

B70 tonnes

C150 tonnes

D375 tonnes

E (or Category 0)1000 tonnes
Drilling (including cementing, completion and workover chemicals) AAll proposed usage to be notified

B3 tonnes

C15 tonnes

D350 tonnes

E4745 tonnes
*These OSPAR categories describe the degree of ecological hazard, with Category A substances considered most damaging to the environment and Category E the least harmful.
**CEFAS. 2000a. Guidelines for the UK Revised Offshore Chemical Notification Scheme in Accordance with the OSPARCOM Harmonised Offshore Chemical Notification Format. London

The British regulations also implement OSPAR recommendations on "trigger tonnages" for some substances, setting a limit on the annual quantity of chemicals used, above which Government approval must be sought.

The result of all the complex form-filling and statement-writing is that the UK Government has a very clear and detailed idea of what developers say they propose to do. For example: The description of muds and chemicals to be used and their disposal must be covered as accurately as possible. If it is proposed to change any muds or chemicals after a direction has been issued, then the Department must be notified.

The completed environmental statement is then circulated to environmental authorities, including non-governmental organisations such as fishermen's organisations and Friends of the Earth, and must also be advertised and made available to the public. At least four weeks are allowed for comments. Then, according to the guidelines:

The Secretary of State will consider the Environmental Statement and any comments received from the environmental authorities or the public before reaching a decision on whether or not to grant consent for a project.

The decision will be published, as will the reasons for the decision and any environmental conditions attached to any consent.

A person aggrieved by the issue of a consent may apply to the Courts for the decision to be quashed within six weeks of the decision being published on the grounds that the requirements of the Regulations were not met.

While the British system appears admirable on paper, in practice such challenges are rare and successful ones even more so, not least because of the legal costs. But the mechanism is there if the public can afford to use it, as Greenpeace did in 1999 when they went to court and proved that the Government had not insisted on a proper environmental assessment prior to proposed oil exploration work on the Continental Slope off north west Scotland. Greenpeace's concerns included the worry that plumes of cuttings might smother rare Lophelia pertusa corals.

Some years earlier, when the Environmental Statements for the Foinaven and Schiehallion oilfields went out to public consultation in the mid 1990s, the author of this paper raised questions about, among other things, produced water discharges from BP and Shell/Esso's FPSO vessels, anchored in 500m-deep water on the stormy edge of the Continental Shelf. It took over a year, a lengthy correspondence, many meetings and an independent, scientific peer review (together with considerable persistence) to persuade the industry that there were problems and the questions should be addressed.(Wills, J. W. G. 1996. BP Come Clean on Foinaven Pollution Risk. Press & Journal, 16 Dec. 1996. Aberdeen)

This was the opinion of a group of Greenpeace researchers after a review of the British offshore regulatory regime in the mid-1990s:

... there is no regulatory body to police discharges or check that discharge regulations are adhered to. 'Operational difficulties' do occur and may result in higher quantities of oil based drilling muds having to be discharged. Drilling muds can be discharged from other sources in addition to that with the drill cuttings. As drill [bits] are changed, muds are spilled onto the drill deck and can be washed into the sea. There is also potential for muds to leak from the drilling collar and to mix with reservoir water and be passed out with the produced water discharges.

Models being developed to control chemical pollution are flawed and unlikely to form reliable regulatory tools. (Reddy, S., et al. 1995. op. cit.)

There is inadequate and incomplete data for the quantities of different drilling muds discharged to the sea with cuttings in UK waters, almost no public information on the actual quantities of WBMs dumped or re-injected and, judging by the official OSPAR statistics, considerable doubt about the fate of large quantities of OBM-contaminated wastes. (See Appendices 2 and 3) The UKCS sector is undoubtedly the largest polluter of the North Sea from these sources, dumping an estimated 5,005 tonnes of oil on drill cuttings during 1998 (See Appendix 5) (the only OSPAR country still doing so) and another 3,187 tonnes of oil in produced water (65.7% of the OSPAR total). In the same year, 61% of platforms exceeding the 40mg/l oil-in-water limit for produced water were in UK waters and between them discharged 86% of the oil involved. (See Appendix 10) Between 1984 and 1998, OSPAR statistics (See Appendix 7) show that the UK Government permitted the reported dumping of a total of 153, 642 tonnes of oil and diesel discharged with drill cuttings, an average of 10,242 tonnes a year. This was 82.6% of the total OSPAR discharge of oil on cuttings of 186,758 tonnes. Because of self-reporting and under-reporting, it is certain that this is a low estimate. There has recently been some improvement but not much: (See Appendices 7 & 8) despite all the current talk of cleaning up the UK's act, the country remains "the dirty man of Europe". The British Government, which receives a large portion of its state revenues from the oil and gas industry, basically trusts the industry to regulate itself voluntarily, through self-reporting and self-monitoring. The results, as depicted in the official statistics, indicate that this trust is misplaced.

Despite this lamentable record, the British authorities continue to make admirable declarations of principle, such as: "The overriding objective of chemical selection should be to use those chemicals which reduce all discharges of oil and chemicals to the extent that they pose an acceptably small overall risk to the marine environment" (see p. 24 of Guidelines for the UK Revised Offshore Chemical Notification Scheme in Accordance with the OSPARCOM Harmonised Offshore Chemical Notification Format. (CEFAS. 2000a. op. cit.)), but when they also state publicly that "proposed discharges" of Group A polluting chemicals in UK territorial waters will merely be "strongly discouraged" (ibid. p.23), rather than forbidden, then it seems reasonable to question the Government's commitment to its duty of safeguarding the marine environment for the public in whose name it operates.

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"Muddied Waters":



List of Abbreviations

Summary of Conclusions

Drilling Waste Streams from Offshore Oil and Gas Installations

The Law on Offshore Wastes Discharges in Different Jurisdictions:

The OSPAR Convention

United Kingdom



United States

Inviting Regulation

Environmental Effects of Drilling Waste Discharges

The SBM Controversy

"Non-Water Quality Environmental Impacts"


Drill Cuttings

Produced Water

Minimising Waste Discharges and Their Effects

Reinjection Offshore

Cleaning Produced Waters

List of Main Sources

Selected References



Articles on Offshore
Oil&Gas; and Environment

Impact of Offshore Oil&Gas; Industry


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