A NEW APPROACH

A NEW APPROACH

A REFRESHING LOOK TO THE FUTURE

Our alternative way of approaching engineering problems results in refreshing designs. Therefore, we are proud to introduce a range of unique products, which, we feel, will help the industry to solve some of their problems.

A New Approach: Concept for Drill Ship / FPSO for Ultra-Deep Waters

It would be a great advantage if we can use existing fixed riser and top tension configurations for ultra-deepwater developments. In drilling-mode preferably vessel heave motion and top tension heave compensation system must result in nearly no vertical riser displacement. Loads on riser and vessel + the requested storage on the vessel due to logistic cost results in vessel designs with large waterline surface which results in large heave displacements. We feel that the solution in drilling-mode must look like a type of vessel with small waterline area, large storage capacity with low VCG and a lot of weight/added mass under the waterline.

We feel that a standard vessel, with 4 columns on hull’s main deck and a moveable deck structure will result in the following advantages:

In drilling mode we have a lot of weight under water and a relative small waterline area.

By transporting the minimum required risers and casing pipe from submerged hull to moveable main deck through an additional center-column we keep the total VCG low.

(With a high VCG the stability requirements do require larger size of the 4 outer columns, which will result in larger heave displacements). In the mid-column we designed a built-in swimmer, which corrects horizontal riser loads and reduces top-tension load dramatically.

The advantage of a moveable deck with a total low VCG also gives the opportunity to sail as a standard ship. This is a relative fast and cheap mode, which dramatically saves time in transit mode. In general:

Subject design needs a lot of ballast to become submerged. It is therefore a small step to convert the vessel from drilling- into FPSO mode. By designing the ballast tanks for storage of ballast water as well as crude oil we are easily able to create a 600.000-barrel of crude capacity. Required equipment, to go into FPSO mode, can be easily installed on the movable work deck without vessel stability problems. When the field is such that it can be explored above concept can start exploring the field within a few weeks.

This is a commercial great advantage. The drilling riser will become a production riser and additional refinery equipment needs to be installed on the moveable work deck by the aid of modules. The huge gantry cranes are able to lift all equipment like templates and modules without the need of crane vessels. A feasibility study showed, in co-operation with an offshore crane manufacturer, it’s technical possible to reach with the hook block depths until 13000’ with a resulting tandem hoist load of approx. 200 Ton with reach of 60’ overboard measured from hull side. Optional: by replacing the derrick by a J-lay tower-performing pipe lay projects are also possible within this concept. Recently we completed concept model testing on subject vessel-design. RAO’s showed that relative heave amplitude stayed well under 0.1 m/min for all governing wave periods.

For more technical information regarding subject concept please don’t hesitate to call.