UKOOA Drill Cuttings Initiative Issue 4 Autumn 2000

The second phase of UKOOA’s drill cuttings initiative is well underway, with progress to report in each of the ten new study and development areas. All UKCS operators with drill cuttings accumulations at production sites are now backing the initiative and have pledged a total of £4.5 million to finance this latest phase of work. Earlier in the autumn an offshore cruise collected new cuttings samples from accumulations on two separate fields. Systems for lifting cuttings from the seabed have been tested at Blyth Dock in Northumberland in advance of the offshore trials in the Spring. Our new look autumn newsletter aims to bring you up to date with all these developments and looks at the programme ahead in anticipation of the study results by the end of 2001.

STUDY AREA UPDATE

To recap, the initiative is focussed on identifying the best environmental options using the best available techniques for the treatment of drill cuttings on the seabed, by examining a number of potential solutions. These are to:

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

* lift the cuttings to the surface and a) reinject them into wells or b) transport them to shore and treat;

The studies in this second phase of work have been grouped to answer questions raised in phase one.

What is the environmental impact of drill cuttings piles?

* What is down there?

In October Rogaland Research from Norway successfully collected samples from accumulations on the Beryl (a large accumulation of cuttings drilled predominently with oil based mud) and Ekofisk (a large deposit drilled predominently with water based mud) fields for laboratory-based characterisation studies. The samples supplement those gathered over the summer from Blenheim and Bladon fields where there are small accumulations of cuttings material with traces of synthetic muds mixed with water-based muds. Existing data for an accumulation at Maureen (small pile drilled with oil based mud) will also be collated and summarised. The data from this range of representative accumulations will help the Industry to build more accurate assessment parameters, allowing future pile samples to be analysed and their likely characteristics defined more precisely (Task1). Data collected in recent months have been acquired in accordance with criteria prepared by OLF (the Norwegian Oil and Gas Industry Trade Association) which is working with UKOOA on the initiative.

* Are the accumulations toxic?

Studies in phase one using standard toxicity tests with marine organisms quantified the toxicity attributable to hydrocarbons within accumulations. Using the same test methodologies, ERT will determine whether non-hydrocarbon components within deposits also have any measurable effects (Task 2a). These data will allow a direct comparison of the potential environmental impacts of oil based and water based mud contaminated cuttings for a range of representative pile types.

*Is the food chain affected?

The objective of this study by URS-Dames and Moore (supported by TNO) is to determine whether cuttings accumulations have any measurable impact on the food chain (Task2c). Samples have been collected and test chambers are being set up to simulate the conditions of oil based mud accumulations on the seabed. The chambers will be left undisturbed until next spring to allow the sediment to stabilise. Laboratory studies will then be conducted to determine exposure effects on various biota, including blue mussels and bottom feeding fish.

* What are the environmental impacts in the context of the North Sea?

Cordah, with support from Akvaplan-Niva of Norway, is developing an assessment of the environmental impacts of cuttings accumulations using the data from Task 1. It will also review these impacts within the context of other environmental issues in the North Sea (Task 2b).

How do the environmental impacts of cutting piles change with time?

* What are the criteria that affect long-term pile characteristics?

To further our understanding of medium and long-term impacts of accumulations, we need to improve our knowledge of how cuttings pile characteristics change over time. Task 3 seeks to establish a model of erosion and recolonisation for accumulations over the long term. A year long laboratory programme managed by Rogaland Research with assistance from SINTEF began in October following the collection of samples from Beryl and Ekofisk. Small-scale experiments are focussing on the effects that various factors (hydrocarbon concentrations, aerobic and anaerobic conditions, for example) have on biodegradation & bioturbation rates, while larger-scale experiments aim to determine erosion rates for undisturbed cuttings samples from the different pile types. At 12 months, this programme is the lengthiest of all the current study areas and will as a result dictate the timing of the final phase two work.

How can we further our understanding of the management options identified in phase one?

* Natural degradation

BMT will use data from Task 3 & 6 to improve and calibrate the mathematical model developed in phase one (Task 4). This will improve confidence in predictions of accumulation geometry, volume, composition and toxicity over time. It will also enhance our understanding of what is likely to happen to the accumulations if they are disturbed, whether by natural events, such as storms or bioturbation, or as a result of human activity, such as fishing or the removal of redundant platforms.

Enhanced bio-remediation

AEA Technology is currently carrying out laboratory-based experiments to identify bio-remediation rates (Task 5a). These will be used in a feasibility study to establish the practicality of using an in-situ bio-reactor system as a technique for degrading contaminants within accumulations. Cost, time and resource consumption estimates will be identified for use in the final comparative analysis.

* Covering

Dredging Research Limited, with support from CEFAS, is focussing on a number of specific issues in its work on covering solutions (Task 5b). These are the geotechnical properties of cuttings piles; the impacts of storms, trawling and jacket removal; leaching; potential collapse scenarios during decommissioning; habitat environment; trial covering; cover construction and materials; monitoring; recurrent costs; and best environmental practice. Information collected will be used to establish design criteria and develop cover designs.

* Lifting, treatment and onward disposal

Tests to determine the environmental impact of lifting cuttings from the seabed are being carried out in two stages under the management of BP (Task 6). The first stage was completed at Blyth Dock in September where onshore trials of potential lifting systems confirmed that there is equipment capable of overcoming water pressure at depth but that significant volumes of seawater would also be raised along with the solids. Equipment to re-inject lifted material into wells was also built and tested. While re-injection should provide an efficient disposal method at BP’s North West Hutton field – where the second, offshore, stage of the trials will take place – this method is not feasible for all North Sea fields.

The offshore trial at North West Hutton is now planned for spring 2001, allowing time for some of the system components to be modified to reduce the amounts of water lifted, and to minimise the weather and safety risks that arise from working over the winter months. Dutch and UK dredging experts have been consulted to assist in maximising the effectiveness of the systems to be tested. Scientific measuring equipment will be deployed around the installation to monitor water quality during the trial, providing critical data to calibrate the semi-empirical disturbance model (Task 4).

ERM (Task 7) is assessing various technologies for the handling, transport and onshore processing of the recovered material. The study will reflect the impact of dealing with the seawater lifted along with the cuttings in the offshore trial and the final results will be fed into ERM’s report when Task 6 is complete.

External Observers

As with all the work to date, the scopes and organisations selected to perform the work have been reviewed by the independent Scientific Review Group. The programme also reflects the input from our Stakeholder Dialogue sessions. These two groups remain very much integral to the initiative process.

Stakeholder Dialogue

In February, we estimated that phase two would take a year to 18 months to complete. We now expect the reports for all ten study areas to be ready by the end of 2001,with the critical path running through the sample collection (completed) and the lab testing programme (underway, see Task 3).

Completion of the phase two work will trigger the next stage of the stakeholder dialogue process. This, together with feedback from the independent Scientific Review Group, will help to inform a comparative assessment of each potential solution against the range of different pile types. The Industry should then be in a position to recommend those solutions which meet the “best environmental practice” criteria.

DIALOGUE SESSION – YOUR VIEWS

We are already thinking about how best to reconvene the stakeholder dialogue group when the results are available and would be interested in your views on the style and content of the event. We would particularly like to hear from you on whether:

* you would like more information in the interim, via the newsletter,the website or in some other form;

* there is a viable alternative to a single day dialogue event, given that there will be a lot of information to assimilate in comparing the different solutions.

Please send your thoughts to Bob Hemmings by e-mail at bob.hemmings@expro.shell.co.uk.

We are also aware that the timing of the research and development programme means that there has not been a face to face stakeholder session since February. So if you would like to know more about what has been going on, please e-mail Trisha O’Reilly at toreilly@ukooa.co.uk or check out our website on www.oilandgas.org.uk/issues where there is detailed information on all the studies and the organisations involved.

11/12/00