What is a shuttle tanker?
Shuttle tankers are specialized vessels that transport oil from offshore oil wells to refineries on shore. They were first used in the 1970s to transport oil in the North Sea, a famously rough area of the ocean. They work to move oil where pipelines are not feasible, such as ultra deep water or where there is severe weather. Shuttle tankers also have the flexibility to deliver the oil anywhere, rather than sending it through a fixed pipeline. Pipeline transport usually involves blending oil as the pipelines don’t have a way to separate which oil comes from which location. Shuttle tankers allow oil to be transported completely segregated. They are easy to maintain, have back-up systems, and can be supported by other tankers, whereas if a pipeline requires repair, it could mean shutting down the entire flow of oil.
Shuttle tanker with close-up of docking mechanism. Image from Wärtsilä.
What makes shuttle tankers unique?
In addition to their offshore prowess, shuttle tankers hold an advantage over larger tankers: they can deliver oil to locations where draft requirements would keep large vessels at bay. They also surpass larger tankers in safety. Crude oil tankers only operate in calm waters, whereas shuttle tankers have dynamic positioning systems consisting of stern and aft thrusters to keep them steady in any situation. According to Rigzone, “Flap rudders and controllable pitch propellers also help to increase low speed maneuverability.” Larger tankers would have to wait out weather conditions, costing a lot of time and money. In some areas where waiting out the weather just isn’t possible, shuttle tankers are the only option.
Shuttle tankers usually get oil from FPSO, or Floating Production, Storage and Offloading facility. These ships are usually attached to multiple wells and are mobile when needed, part of the same flexible supply chain as shuttle tankers. The loading system is usually on the bow of the tanker, a safe place to connect and load oil, even in harsh conditions. There are other methods of loading such as keel, but it depends on the field. A single point mooring system connects the tanker, allowing some movement. Shuttle tankers use their dynamic positioning systems to stay in place and reduce wear and tear on docking systems while loading and unloading.
“BW Pioneer FPSO
Source: dynamicpositioningnews.com”. Image from Rigzone.
How does the dynamic positioning system work?
Dynamic positioning uses multiple thrusters underneath the vessel to provide extremely accurate movement or station-keeping. These thrusters are computer-controlled, receiving inputs from wind, wave, and other sensors all over the vessel. Redundant DP systems are the most common type, as systems without redundancy could be taken offline by one component failure. DP2 and DP3 systems are redundant systems. DP2 systems are able to withstand component failures and continue operating. DP3 systems are able to survive flood or fire in a compartment and continue operation. OneStep Power tests DP2 and DP3 power systems, verifying them for fault ride through. These systems need to be regularly tested to ensure a fault won’t take them offline. If a fault takes a redundant DP system offline, the crew may lose control of the vessel as happened in the movie documentary Last Breath.
Dynamic Positioning System forces. Image from Kongsberg.
Shuttle tankers and other dynamically positioned vessels
Shuttle tankers began use in the 1970s to deliver oil in an area with severe weather. They are still used for this purpose, but have become a great option for many aspects of offshore drilling. First, the flexibility of a shuttle tanker to operate in any conditions, at multiple small wells is unmatched. They have dynamic positioning, meaning they can operate in more locations with better station keeping than larger tankers. Their lower draft requirements further opens the number of locations to which they can offload. Their safety record is also phenomenal as they are smaller, more maneuverable vessels with back-up systems. They even provide segregation of smaller batches of oil that would otherwise be combined in a larger pipeline. A lot of attention is given to huge oil rigs and underwater pipelines that transport millions of barrels of oil, but shuttle tankers play an important role in moving oil where it couldn’t otherwise be transported.
If you’d like to learn more about other types of dynamically positioned vessels, check out our article on 22 types of dynamically positioned vessels where we talk about all sorts of vessels including offshore support, cable lay, construction, naval vessels, and even cruise ships. You can learn more about OneStep Power’s proprietary testing technologies on our services page.