Drilling rig on a Steel Caisson is one of the drilling rig design concepts for offshore shallow water environments.
1. Water depth range: 5 – 100m however must be designed for a limited water depth range, unless berms are considered. More study required to ascertain minimum water depth capability of concept with & without rig installed for positioning
2. Low environment impact.
3. Suitable for ice. The concept has been used successfully in the Beaufort Sea and Canadian Arctic, though in deeper water e.g. Hibernia, Molikpaq etc.
4. Fabricated to be floated into shallow water, either with the rig on, or to be installed after caisson
on location. Caisson can be ballasted for stability
For shallow water, would need to be steel to be able to float in. For deeper locations, Possibility of using concrete, rather than steel, as caisson material.
Caisson can be designed to withstand ice loadings. Could be circular with ice-resistant concave sides
Requirement to fabricate in the Caspian, with associated cost and complexity
5. Rig move not feasible during the winter season. Design Caisson based on rig & facilities layout & loading, re-supply systems and water depth range required.
Other drilling rig design concepts for shallow water depth environments will include:
1. Land rig on artificial island
2. Land rig on barge (with optional submerged caissons)
3. Swamp Barge (With Optional Submerged Caissons)
8. Steel Caisson with Drilling Rig
9. Modularised and Pile Elevated Drilling Rig
10. Drilling Rig on Pre-Installed Piles and Modules
11. Jacket Supported Offshore Rig
12. Posted Barge With Land Or Modular Rig
13. Heli-Rig
14. Submersible