Operators examine options for shuttles in GOMNews // September 22, 2000
ABS says both shuttle tankers and ATBs will be subject to the requirements of OPA 90 and will therefore have to be doubled hulled. They will also have to be crewed by US nationals and US-flagged.
According to ABS, based upon their widespread use elsewhere, the Coast Guard regards ATBs as acceptable for use in the new role, but is concerned about the use of older tankers as shuttles - including single hull ships converted to double hull status.
Another key issue is that shuttle tankers operating in the US GoM will need to comply with the Jones Act. This implies that the tankers must be constructed in the US, be US-flagged, and employ local crews in US waters.
This could make shuttle tankers for the Gulf of Mexico higher than ships built elsewhere. One potential operator - Edison Chouest Offshore - has suggested construction of a 500,000-barrel shuttle tanker could cost $116m to $150m.
The cost of shuttle tankers will be particularly important, because, typically, after an oil field has come on stream, production will peak quite quickly afterwards, then slowly decline. As Edison Chouest Offshore's Roger White explains, what the oil companies don't want is to be left in a position where the oil they produce effectively costs more and more to produce and transport as production declines.
A low cost alternative, which is the subject of considerable interest, is the use of Articulated Tug/Barge (ATB) vessels instead of conventional shuttle tankers.
The primary reason for using an ATB rather than a conventional shuttle tanker is that they are less expensive to build, and have lower crew costs - an ATB with the same cargo carrying capacity would need just seven crew, compared to around 27 on a shuttle tanker.
Using ATBs instead of conventional shuttle tankers would certainly reduce the capital expenditure required to transport oil in the Gulf of Mexico, and although not widely used elsewhere, they have a proven track record in US inland waters.
Seasonal storms apart, the waters in the Gulf of Mexico are relatively benign, making them suitable for ATBs. Another important factor is that the distances over which crude would have to be transported are not great - from one of the furthest known fields, called Crazy Horse, to the coast is 400 miles, so the somewhat slower speed of the ATB is not an issue.
Most advocates of ATBs say they could also be used to perform other tasks in the Gulf of Mexico. They could tow a FPSO in an emergency, such as a hurricane; could be used to tow other production platforms; could provide subsea support; or act as supply vessels.
"If a storm is predicted, the tug in an ATB can tow a FPSO to safer waters", says Roger White at Edison Chouest Offshore. "You have to remember that these are 18,000-20,000hp ocean-going tugs, and there are plenty of other tasks they can take on apart from transporting crude oil".
White says he also foresees that forebody of an ATB shuttle tanker being used as an FpSO. "The small 'p' indicates that we think the hull of the barge could also be used for extended well testing with limited production and storage", said White.
Hill's company is currently developing ATBs for four clients, including 500,000bbl capacity ATBs that could shuttle crude from FPSOs in the Gulf of Mexico to refineries ashore.
"A hallmark of this concept, and one way it differs from an Integrated Tug/Barge (ITB) is that ATBs are designed for maximum speed instead of maximum towing stability", explained Hill.
In an ITB the tug and barge are rigidly locked together and for practical purposes are a single unit. In an ATB, however, the units are joined together via an articulated connection system. "Effectively, what you have is a hinge between the tug and barge, which allows movement in the form of fore and aft pitch," explained Hill.
There are many different ATBs designs, explained Hill, but all have hinge-like connections, which provides the ATB with the kind of sea keeping required for use in the Gulf of Mexico.
Yards such as Atlantic Marine suggest that the cost of building an ATB could be around $80m, and savings could also be made in the operation of these vessels. A typical crew for a tanker could be as high as 27 people, whilst for an ATB it could be just seven personnel, which translates into around a $2m cost saving per annum in crewing costs.
Not all owners will necessarily want to choose ATBs, however. Simon Duncan, Marine Operations Manager at Skaugen Petrotrans Distribution, part of the Skaugen group, says his company has entered into a partnering agreement with Navion, the well-known Norwegian North Sea shuttle tanker operator, in order to capitalise on Navion's considerable experience in the field.
Skaugen is evaluating both conventional shuttle tankers and ATBs, and could opt for standard shuttle tankers in order to ensure that it can use the ships elsewhere than in the Gulf of Mexico.
For his part, Duncan says a conventional shuttle tanker could cost around $120 million, whereas an ATB might come in at $80-90 million, depending on size and specification.
Skaugen has developed a preliminary design specification for a 105,000dwt shuttle tanker, a modified Aframax ship with a length overall of 245m and a beam of 42m. This DP2 class design would have a capacity of around 550,000bbls.
"All of the potential operators in the Gulf of Mexico want to be able to offer the oil companies the most economical means of transportation", says Duncan, "but ATBs would not be well-suited to use outside the Gulf of Mexico. If we go down the route of building conventional shuttle tankers modified for the Gulf of Mexico, we can also trade them on the spot market", he explained.
Like many other operators, Skaugen also set out to design a 350,00bbl ATB, but soon found that what the refineries in the Gulf of Mexico really want is parcels of around 500,000bbls.
As Trey Leblanc, Marketing Manager at Atlantic Marine shipyard points out, there is little point in using two smaller vessels to provide the kind of parcel size the refineries want because doing so would increase costs, the amount of oil-related trafficin the region, and the potential environmental impact.
Two more companies that have teamed to develop shuttle tankers for the Gulf of Mexico are Conoco and Maritrans.
Conoco and Maritrans are examining versions of shuttle tankers and deepwater loading systems that have been used elsewhere - Conoco's fleet of double-hulled ships includes Rangrid, a shuttle design expressly for the Heidrun field in the Norwegian sectorof the North Sea.
Together the companies are discussing a variety of options including conventional newbuilds, ATBs, and the acquisition of existing tonnage, which could be modified for use in the Gulf of Mexico. This latter way forward would also enable the Conoco-Maritrans team to get shuttle tankers into service very much more quickly.
Just how many shuttle tankers will be required is open to question. The number required would depend on individual fields, their location, and what type of production platform was required, but a good rule of thumb is that 3-4 units would be required perplatform - one loading, one discharging, and two in transit to and from the platform.
Most potential operators and some of the yards involved that hope to build them - yards such as Ingalls, Avondale, NASSCO and Kvaerner Philadelphia - say 30-50 ships might be required. At least one owner has been discussing orders for up to 14 ships withsome of the American yards.