Drainage Systems for Drill Ships and Platforms
Oil rig view
GEA has developed several methods for processing drilling mud and water on the drilling decks of drilling platforms and drilling vessels; these range from a simple combination of decanter and separator, the upstream installation of a skimmer tank right through to recovery of the valuable heavy mineral barite. All three methods have already demonstrated their worth in the rough working environment of drilling platforms.
Combination of decanter and separator
Drilling platforms and drilling vessels pose particular requirements with regard to the processing of bilgewater and drilling mud. The platforms and the vessels are in principle split in two. On the whole, it is necessary to treat water which is equivalent to the bilgewater on normal vessels and which can be treated by corresponding means. The tried-and-tested bilgewater separators from GEA are suitable for this purpose; they are currently being used in hundreds of applications on all types of vessels.
The challenge on drilling decks is somewhat different, though. The process of changing drill pipes results in large quantities of drilling mud with a very high solid content on the deck. Drainage water poses major challenges in terms of processing. The composition of the drainage water varies considerably. Normal bilgewater processing systems are not suitable for this purpose. In this case, a good solution is to use a combination of an upstream decanter, which removes the coarse solids, and a downstream separator. It is of course self-evident that this complete system has to be designed with ATEX explosion protection. The combination of a decanter and separator has already demonstrated its worth. The required MARPOL figure of less than 15 ppm oil in water is attained reliably and consistently. Drilling companies have already used this technology of GEA on many occasions in the past for building new platforms and drilling vessels or retrofitting the equipment.
Upstream skimmer tank
The experience gained with the combination system decanter / separator has been used by GEA in conjunction with the drilling companies and shipyards in order to further develop and improve the drainage system for the drill decks. The use of an upstream skimmer tank was a good solution for the preliminary separation of very large particles such as stones and beverage cans as well as floating solids.
Additional recovery of barite with classifying decanter
Special treatment is required for the heavy mineral barite (barium sulphate), which has a minimum specific density of 4.20 g/cm3. The comparatively expensive barite is added to the drilling mud on board in order to thicken the drilling mud. This rare and valuable mineral would have to be disposed of together with the dried drilling mud if it could not be separately precipitated. However, it is far too precious. In order to recover barite to be used again as an addition to the drilling mud, GEA has developed the possibility of installing a special classifying decanter upstream of the separating decanter. This special decanter removes only very heavy solids from the mud. A GEA rigMaster CF 4000 from the new ecoforce decanter generation is used for this application – with the inherent advantages such as robust operation and maximum availability, high throughput capacities, excellent separating efficiency and low energy consumption. The separation of barite is currently also being used by several drilling companies.
Composition varies considerably
