An oil containment system originally developed to recover oil leaking from shipwrecks has now been adapted to recover oil leaking from well heads below drilling and production rigs.
The development of this new system was partly motivated by the Deepwater Horizon rig disaster in the Gulf of Mexico and the designers are confident that the system could help contain oil leaking from future rig disasters.
The DIFIS (Double Inverted Funnel Intervention System) system was originally developed with EC funding as a way to cope with oil leaking from wrecks in deep water such as the Prestige that sank off the coast of Spain. It comprises a bell-shaped fabric that is put in place over the wreck and tethered to the sea bed. This collects any oil flowing out from the wreck and from the apex of the tent-like fabric the oil is channelled into a flexible tube where the oil flows upwards as it is lighter than water.
At the top of the tube there is another inverted tent-shaped fabric structure where the oil collects, displacing the water inside the structure. This tent-shaped structure is located well below the surface of the sea so that it is not influenced by the sea conditions above and from this structure a pipe allows the collected oil to be taken on board a shuttle tanker or other vessel.
The system has been model tested by a consortium put together under an EC grant. The Dutch consultancy MARIN was involved as well as oil companies and after this initial work that was funded to the tune of €3.5m, the project is ready to move forward to full scale trials.
The system can be deployed to most oil pollution sources in waters from 400m to 4,000m deep and it does not interfere with the wreck or pollution source. It can be put in place using conventional vessels and technology although more specialised equipment would be required for a very deep water installation. It is claimed that the system would be rough weather tolerant because it is installed well below the surface and the collected oil can be recycled and used as normal.
The DIFIS team estimate that it would cost around €20m to construct and deploy a full scale system which would be air transportable for rapid deployment.
Any leak from a wreck would be pure oil but when a leak occurs at a wellhead there can be a high proportion of gas. As this gas rises it expands and thus accelerates, which not only stresses the DIFIS installation but would also make collection at the surface difficult. To overcome this DIFIS has now modified the system to include valves in the pipe riser that would reduce the speed of the gas which could then be vented at the surface or collected separately.
It would be possible to install the DIFIS as a permanent installation below a drilling rig but the cost could make this prohibitive. A more likely scenario would be for the anchor points for the system to be put in place as part of the initial well development and then the DIFIS could be installed rapidly in the event of a blow out. It is likely that if the funding is available the DIFIS would be kept ready as an air-portable system for rapid deployment when required.
Dr.Fivos Andritsos from the European Joint Research Centre in Italy commented: “We have had interest from the salvage company Smit and the Brazilian oil company Petrobas is also interested so we are hopeful that future funding will be available. The next stage is to make presentations to oil companies and other interested parties to find a way ahead.”
Source: www.maritimejournal.com; Dag Pike