Decommissioning, plugging and abandonment, well workovers, EOR, and even offshore renewables maintenance could be performed from the dual decks of the CDC Heron. Elaine Maslin reports.
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The CDC Heron multipurpose vessel design. Image from Celtic Design Consultants. |
UK-based Celtic Design Consultants (CDC) has developed a design for the ultimate vessel of opportunity in less than 400ft water depth, for plugging and abandonment (P&A) work, as well as, cementing and casing work, offshore renewables operations and anything else operators might want to do, the company says.
The multipurpose jackup concept, described as a “services delivery platform,” is a self-propelled DP2 capable unit with four jackup legs supporting a hull. It has a main deck and second self-elevating deck, which can be jacked up to 130ft above sea level. The self-elevating deck also includes an extending deck, which can extend over oil and gas platforms for well workover work or wind turbines, to perform maintenance on turbine generators and blades, without needing rope access crews, and can support up to 500-tonne in equipment, such as a crane, mast or well workover equipment. The vessel concept has built in tanks, space for high-pressure pumps and low pressure mixing services for bulk and mud, which could be used for enhanced oil recovery operations as well as other tasks, as well as a moon pool for subsea activities, including P&A. It has 3000sq m usable deck space and can carry over 1400-tonne deck load.
A blank canvas
The concept, called the CDC Heron, started life back in 2007, but has been developed by the CDC team specifically to what it is now since about 2012. “It is a vessel providing a blank canvas,” says John Davies, CDC’s managing director. “However a client wants to configure or whatever the clients wants to be put on, can be put on.”
Davies says all the technology used on the unit is established and proven. When it comes to well work and P&A, he says it can reduce costs, by dispensing with a costly drilling rig once it has completed drilling. “With a drilling rig, once the drilling is complete, 80% of the rig equipment and functionality is no longer needed. So you can dispense with the rig and utilize this unit to look after the well for the rest of its life.”
He says, compared to using a jackup rig for P&A work it could save about US$102,000 per day, based on a $80-100,000 day rate for the CDC Heron, due to eliminating the need for tugs to move the unit and reducing equipment change requirements due to larger capacity and deck area and having an increased accommodation capacity capability, at 120. It could also be used as an accommodation unit, providing North Sea-standard accommodation for upwards of an additional 300 people, CDC says.
Further, because the secondary deck can elevate to desired working height, operations don’t have to rely or cranes or rope access work, which increases operational uptime, Davies says.
Tendering activity
CDC has submitted a tender for use of the vessel as part of a package with a major oilfield services company for a five-year, plus extension options, P&A campaign in the UK southern North Sea. Should the contract, or letter of intent, be awarded, the finance would be in place to build the first CDC Heron, a task which would take two years, Davies says.
As well as interest from the UK southern North Sea, Southeast Asia has shown interest in using the vessel, Davies says, due to their current use of tender barges, which have limited operational windows due to seasons and weather.
The firm, which has achieved ABS’s approval in principle for the vessel design, also has patent pending for the vessel’s second and extending deck design. CDC have also submitted a patent for a new jacking system approach. There is also an accompanying new leg design on the drawing board. which would enable it to work in up to 600ft water depth and be retrofitted on to existing jackups, Davies says.
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