9. Cuttings re-injection

The process of grinding drill cuttings to form a slurry which is then pumped downhole, either into a dedicated disposal well or into the annulus of an existing well, has been used since the early 90's and is a mature technology. This process of Cuttings Re-Injection has some major benefits compared to the alternative containment option of transporting cuttings to shore for treatment and disposal. Firstly the Cuttings Re-Injection process is able to handle volumes of drill cuttings compatible with the fastest realistic rates of drilling even in the larger 16" or 17 ½" hole sections (this can be 30 - 40 tonnes per hour), unlike the ship to shore option. Furthermore, because there is no requirement to move the cuttings off the rig there are no demands on crane facilities, deck space or supply vessels and perhaps most importantly no vulnerability to weather related downtime. The last factor is the largest uncertain variable in the planning of containment operations, and may correspond to drilling shut downs where the ship to shore option is used in the winter months. Finally, the re-injection option has the benefit that where the re-injection facility is available it may be further employed for the disposal of other problematical waste streams such as low radioactivity LSA solids controlale or even produced water.