How to Move a Deep Water Drill Rig
The international oil industry defines “deep-water” as those offshore regions where water depths exceed 600 feet. Oil drilling in water depths between 600 and 8,000 feet is conducted mostly from semi-submersible drilling rigs. In addition to their ability to drill in deep-water depths, these rigs are maneuverable from one drilling location to another. They work on the principles of buoyancy and ballast. The rig is a combination of an operations deck with 6 to 8 pontoons, or legs, fixed below it. When filled with water, the legs act as ballast tanks and submerge below the sea surface and provide stability. When filled with air, they allow the rig to float on the sea surface and be moved to any location.
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Things You'll Need
- Marine Scientists
- Security experts
- Semi submersible rig
- 2 to 6 towing tugs
- 2 to 6 supply vessels
- 2 to 6 escort vessels
- Crew for rig and other vessels
- Anchors and anchor lines between rig and towing vessels
- Anchors and anchor lines between rig and sea floor
- Navigation and positioning systems
Instructions
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Preparation
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1
Plan the marine route between the rig’s current drilling location and its next location. Hire marine scientists to study the expected sea and weather conditions along the route. Hire security consultants to examine the security aspects along the route such as piracy. Inform maritime and government authorities of the route.
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2
Release anchors between the rig and the sea bed that attach the rig to its present location. Empty the ballast tanks, the pontoons, of water. Allow the pontoons to rise above the sea surface until the entire structure is visible.
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3
Move towing tugs, supply vessels and escort vessels close to the floating rig. Attach anchors between at least two of the towing tugs and the rig. Start the towing tugs and other vessels to move the rig to its next location. If the rig is of the design that allows it to move without the aid of other vessels, start up thrusters on the rig and move to the next location with the aid of an onboard navigation system such as GPS. Ensure supply and escort vessels remain with the rig even if it is moving under its own steam.
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4
Halt the tugging, supply and escort vessels and rig at the next location. Use navigation and positioning systems to ensure an accurate positioning at the new location. Detach the anchors between the vessels and the rig. Fill the rig’s pontoons with seawater. Allow the rig structure slowly to sink below the seas surface until the pontoons submerge below the sea surface but the operations deck remains above it. Attach anchors between the rig and the seabed.
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Tips & Warnings
Ensure that a contingency plan is in place in case of unexpected extreme weather or sea conditions. Delays in arrival at the new location could result in financial penalties for both operators and contractors in the rig moving operation.
Unexpected sea conditions can topple the rig during movement. Anchor lines between the rig and towing vessels may snap and cause crew injuries or fatalities.
References
Resources
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