17. Slurrification and discharge

This option has considerable potential for a low cost, highly effective solution.

The main concern associated with the discharge of cuttings contaminated with synthetic muds is that the base fluid can take a long time to degrade, especially when trapped inside a substantial cuttings pile. Sea bed contaminated with synthetic mud recovery times can be many tens of years. It is considered entirely possible that if cuttings are ground to produce a fine particle slurry prior to discharge the greatly increased suspension time of the particles before settling to the sea bed might result in significantly increased rates of degradation. Furthermore, although the area over which the cuttings are dispersed will be much greater, the resulting in very thin cuttings layers on the sea bed will be likely to continue to degrade quickly and have a minimal and short lived effect on the sea bed.

The process of slurrification prior to discharge has already been practised, primarily to avoid the production of cuttings piles which can be problematical to sub sea well heads. The ultrasonic slurrification unit is ideal for this application and can easily be installed between the cuttings ditch and discharge chute.

Very little is known, however, about the impact of slurrification on degradation rates and the process may be criticised for dispersing the cuttings waste over a wider area, possibly into foreign waters, and a parallel with the banned process of sewage discharge has been drawn. It is possible, however, that this process may represent a cheap solution with very low environmental impact and a study to determine the actual behaviour of slurrified cuttings on the sea bed is strongly recommended.