A new type of budget-priced, simple, decommissioning semi-submersible is being developed by a veteran of the North Sea.
He’s a Scot, was raised on Clydeside and worked in the shipyards prior to getting involved with offshore engineering and, 35 years ago, originated the simple box-section, low-cost semi-submersible concept known as the MPSS.
Though no tonnage was specifically built to that design, it appears to have inspired others to mimic the approach, perhaps obliquely copying the MPSS into a number of current drilling rigs and floating production units. Or at least that is the perception, if not reality.
Craig Lang, an exile who lives in the US these days, is back; this time with Nessie, or to be more specific: Novel Extended Semi Submersible Installation/Decommissioning & Recycling (NESSI/D).
Not only that, the CEO of Seaways Engineering will be back in Aberdeen for Offshore Europe week to promote the design, together with an accommodation vessel variant courtesy of C-Mar on Regent’s Quay.
Nessie is a stretched, scalable MPSS . . . a basic six poster with a “ring” pontoon, “gated” at one end.
It resembles a classic floating dock in the way it behaves, but without the plated-in sides or bottom. It will apparently be cheap to build and, like the original MPSS, could be built by any competent shipyard using flat plate.
It will of course be self-ballasting and be offered with or without propulsion and Lang currently sees a need for at least two Nessies. The self-propelled variant would be equipped with a family of six azimuthing thrusters rated around 60-tonnes apiece.
He describes it as a floating dock and it is being designed for topsides removal, jacket lifting and rotating underwater (to reduce stress on such structures) and transit and delivery of cargoes to dry-dock for dismantling and recycling, or refurbishment and re-use elsewhere.
The view is that refurbished GOM jackets will find a ready market in the Mexican sector, which is now opening up in a significant way and the Lang preference is that a UK design house takes on the detailed design work for Nessie.
Taking a leaf out of the book of salvage hero Ernest Cox, Lang has determined that compressed air will be used to de-ballast a jacket for neutral buoyancy during the lifting and rotation process.
For readers who are unaware of Cox, he was the brains behind raising the scuttled German Grand Fleet from the bottom of Scapa Flow post WWI.
Nessie would also be capable of installing new production facilities and will apparently not require motion compensation systems because of its inherent stability characteristics.
The MPSS concept is being worked up in San Diego and at Blyth. Extensive modelling is under way and the next stage is to raise the backing to build a large model for full test-tank trials.
And the capital cost? A few hundred million US dollars versus a reported $3billion for the gigantic Allseas vessel Pioneering Spirit (formerly Pieter Schelte and dubbed by Forbes on December 20 last year as “Big Oil’s $3Billion Homage To A Nazi War Criminal”).
However, Nessie remains an idea whereas the Allseas ship is in the late stages of fitting out. Likewise, there are various Dutch and Italian-owned heavy-lifters already active in the market.
On the other hand, the decommissioning market is measured in decades, which suggests scope for new entrants to that growing market and where oil companies are now desperate to slash costs across the board, including infrastructure disposal.
Both Nessie and Pioneering Spirit are novel and each is backed by a lot of maritime applications experience. The Allseas track record is well told; but Lang’s, through Seaways Engineering International, is maybe less known.
Credits Lang lists include:
MPSS-rig pontoon semi-submersible – inventor
Conoco Belanak FPSO/marine systems
Conoco Hutton TLP mooring – inventor
Apache reelship – inventor
Steel catenary riser development
Hughes Glomar Explorer
Texas Galley – FPV North Sea
Alcoa Seaprobe/Woods Hole
Alcoa Midwife recovery vessel
An advanced pipeline plough handling system
Very recently – floating production semi with storage for 300,000 barrels with steel pipe moorings for ultra deepwater application
When Lang first offered the MPSS to the marketplace in 1988, the offshore industry was in dire straits following the global oil price crash of 1986.
The idea was that it could be completed as a mobile rig, production unit, service vessel and so-forth. Moreover, it was designed to be built in pretty much any reasonably competent shipyard, even allowing for the need for coded welders.
In a paper prepared for the Institution of Engineers and Shipbuilders in Scotland, Lang and others went into significant detail about the concept.
The basic platform would be 90m square, by 56.25m high. Initial development had been supported by Texas Eastern North Sea Inc. and, in those days, a target construction cost of £1,000 per tonne based on the mass manufacture of basic fabricated steel boxes . . . 7.5m was selected as the basic building block . . . that could then be put together in whatever configuration was required.
The design offered a large deck area of 8,100sq.m and a payload capacity of 12,000 tonnes with “ample internal storage”.
However, it could be made larger, or smaller, possibly configured as a gravity base structure and be completed as a flotel (the 1,000-bed Safetel concept).
The MPSS, as it was called, displayed stable and apparently acceptable motion characteristics; both calculated and in trials.
Texas Eastern sponsored further feasibility designwork, which was carried out by consultants at Atkins Oil & Gas Engineering.
Conoco (UK) also sponsored the manufacture, testing and analysis of a 1/100th scale plastic model of the MPSS at Glasgow University, including carrying out static tests to simulate a corner “grounding” condition and wave tests in beam seas and 45-degree seas with moderate fatigue level seas (20m full scale).
Even so early in its development, MPSS was demonstrated to be “hydrodynamically viable” and arrangements had been made with Lloyd’s Register to review the design.
Then it all went quiet. Out of frustration, in late 1994, Lang got in touch with the Press & Journal in the hope of capturing interest. Why was it that the Multi-Purpose Seaways Semi-submersible (MPSS) had not captured market attention?
The P&J carried an article about the MPSS dilemma in December that year.
It seemed that, despite quotes being sought and secured from a number of yards, including Appledore, Harland & Wolff and Scott Lithgow, no one was interested, despite the CRINE movement with its 25% headline CAPEX cost reduction target for new North Sea developments.
Nothing happened; it all went quiet again.
Early this year, Lang got back in touch with the P&J asking: “Remember me? Remember the MPSS design that you wrote about years ago?”
Lang said that, despite the best efforts of those involved with Seaways over the years, the MPSS had never been built. However, it has featured favourably in conferences including at the 24th Conference on Offshore Mechanics and Arctic Engineering – 2005.
Lang is a naval architect by discipline and played an apparently pivotal role in making the famous reel pipelay ship Apache the success that it was.
He lives in San Diego these days and hasn’t given up on the box-section beast which was first sketched out in 1980.
Indeed, in a recent e-mail he wrote: “I have just completed an application for a patent for a platform removal vessel which is an extension of the MPSS.”
And its name is Nessie.
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