Monday 11 December 2000

UKOOA Pushes Ahead With Next Phase of Drill Cuttings Study

UK offshore oil and gas companies have pledged a further £4.5 million to finance a second phase of research and development in the joint industry initiative to find solutions for dealing with accumulations of drill cuttings on the seabed.

The UK Offshore Operators Association (UKOOA) drill cuttings initiative, which has the backing of all operators with drill cuttings accumulations at production sites on the UK continental shelf, has awarded contracts in ten new study areas. The initiative is also supported by the Norwegian Oil and Gas Industry Trade Association, OLF. The final reports are expected by the end of 2001.

A range of potential solutions for dealing with cuttings accumulations on the seabed is being studied. The possible solutions are:

* To leave the cuttings in place and a) allow natural degradation, b) apply enhanced bio-remediation or c) cover;

* To lift the cuttings from the seabed and a) re-inject them into wells or b) transport them to shore for treatment.

The new programme builds on the findings of the first study phase completed earlier this year and reflects feedback from meetings with stakeholders and an independent group of scientists who are monitoring the initiatives progress.

It combines survey work with laboratory testing and field trials, enlisting research organisations from around Europe including Rogaland Research, CEFAS, TNO and SINTEF - to answer the following specific questions:

* What is the environmental impact of cuttings accumulations?

- Data are being collected from samples of accumulations at five North Sea fields (Ekofisk, Maureen, Beryl, Blenheim and Bladon ) which offer a representative range of different cuttings accumulation types and sizes.

- Environment and Research Technology Ltd is carrying out research to determine whether the accumulations drilled predominantly with water based muds are toxic while URS-Dames and Moore is establishing whether cuttings drilled with oil based muds have any effect on the food chain;

* How does the environmental impact of cuttings accumulations change with time?

- Norways Rogaland Research has embarked on a year long study to determine how the characteristics of accumulations change over time. The results will be used by BMT Marine Information Systems to fine-tune the mathematical model developed in phase one which predicts the processes of the degradation, erosion and re-colonisation by marine flora and fauna. The model will also help to improve understanding of what is likely to happen to the accumulations if they are disturbed, such as by storms, trawling or during the removal of redundant platforms;

* How can we improve our understanding of the environmental impacts of the different management options?

- Tests to determine both the feasibility and the environmental impact of lifting cuttings from the seabed are being carried out in two stages under the management of BP. The first stage was completed at Blyth Dock in September, with the second stage scheduled to take place offshore at the North West Hutton platform in the spring. The onshore trials confirmed that there is equipment capable of overcoming water pressure at depth but that significant volumes of seawater would be raised along with the solids. ERM is assessing various technologies for the handling, transport and onshore processing of the lifted material.

- AEA Technology is determining bio-remediation rates from laboratory-based experiments before assessing the feasibility of using an in-situ bioreactor system as a technique for degrading hydrocarbons within accumulations.

- A team led by Dredging Research Ltd is exploring the possibility of covering the accumulations. Laboratory experiments assessing leaching potential is helping to establish design criteria and develop possible cover designs.

Ian Silk, chairman of the UKOOA drill cuttings initiative, said: The first phase identified a number of gaps in our knowledge with regard to the present and future impact of cuttings accumulations, and the benefits and feasibility of the candidate management options. The second phase aims to plug those gaps, by sampling and analysing cuttings accumulations and developing the management options further to allow comparative assessment to be undertaken.

Completion of the second phase will trigger the next stage of the stakeholder dialogue process which, together with the feedback from the independent scientific review group, will play an integral part in the final comparative assessment of the various potential management options, he added.

Note to Editors

1. The UK Offshore Operators Association (UKOOA) is the representative organisation for the UK offshore oil and gas industry. Its 30 members are licensed by the British Government to explore for and produce hydrocarbons in UK waters.

2. The UKOOA Drill Cuttings Initiative was launched in June 1998. It is guided by the OSPAR principles of BEP (best environmental practice) and BAT (best available techniques) and will provide information to inform national and international decisions on how best to deal with cuttings accumulations on the seabed.

3. Phase I of the drill cuttings R&D programme was carried out between April 1999 and February 2000.

The main findings are:

Accumulation content:

* What we know about the physical characteristics of cuttings accumulations has been improved but there is still a shortage of reliable data.

* UKCS cuttings volumes at production sites are estimated at 700,000 m3 in the central North Sea and 500,000 m3 in the northern North Sea.

* The characteristics of each accumulation varies greatly, according to the types of muds used while drilling, the volumes drilled, cuttings discharge methods, water depth and currents.

* Further surveying and sampling of accumulations will be required, using a representative base range of cuttings piles with different characteristics.

Environmental impact of accumulations:

* Environmental impact depends on the nature of the source material, the pathways between the source and its immediate environment, and the receptors, the marine organisms that could potentially be affected.

Source

- Total hydrocarbon concentrations within accumulations exceed the no effect concentration for typical marker species, such as for mud shrimps.

- Further research is required to establish whether pathways exist from the accumulations to marine life in the vicinity, which would be necessary for any further ecotoxicological effect.

Pathways

- Heavy metals do not seem to be leaching from the accumulations, nor indeed do they appear to affect marine life, as long as the pile remains undisturbed.

- Hydrocarbons within the surface layers (the top 5mm) are decomposing rapidly and re-colonisation is being observed. Further work is required to quantify the rates of these processes.

Receptors

- Bio-diversity is reduced within the vicinity of the accumulations.

- Opportunistic re-colonisation by bristle worms occurs within one year of cuttings discharges ceasing.

Management Options:

* There is no proven remediation method

* Enhanced bio-remediation is too theoretical as yet, but merits further investigation

* Covering the drill cuttings accumulations is still a potential solution

* If lifting to the surface is attempted, there are issues related to the secondary contamination of seawater as a result of the accumulations being disturbed and to the significant volumes of water which would be pumped up along with the solid materials

* Re-injection to the reservoir is technically feasible but not possible for all North Sea fields. Its legal status is also uncertain

* Natural degradation also merits further consideration

A summary report by project managers Det Norske Veritas (DNV), as well as the full text of all the phase one research reports, are available at the UKOOA web site.

For more information, please call 020 7802 2400.