J for Diana

Published October 31st, 2000 - 02:00 GMT

Using the new J-lay system, the Saipem 7000 has successfully completed an ambitious project in the Gulf of Mexico for ExxonMobil. Saipem’s North Atlantic Director Hugh O’Donnell tells us about the operation and the prospects for the company’s renovated installation vessel, now the most powerful in the world. 

 

“A turning point for Saipem” was how Chairman Stefano Cao described the Diana Hoover contract when it was awarded to Saipem by Exxon in 1997. It provided for the installation of the facilities for developing the very large Diana Hoover field in the deep waters of the Gulf of Mexico.  

 

To carry out this formidable assignment, Saipem added the new J-lay system to the Saipem 7000, making it the most powerful installation vessel in the world, with a stream of opportunities in the next 5-10 years. 

 

Saipem's North Atlantic Director Hugh O’Donnell takes up the story. “Diana has a production capacity of some 100,000 barrels per day of oil and 325 million standard cubic feet per day of gas. In 1,480 meters of water, it is perhaps the most challenging field of its kind in the world. Fields have been discovered at greater depths than Diana, but not developed.” 

 

When Saipem was awarded the contract the design had barely commenced. Early sketches of the development plan showed a moored spar (Exxon call it a deep draft caisson vessel, or DDCV) with oil and gas export lines (eventually they both became 18”) and 10” and 6” flow lines from remote drilling centers. 

 

“Exxon (now Exxon-Mobil) gave us the opportunity to bid on whatever scope of marine work we thought we could really add value to,” says Mr. O’Donnell. Saipem bid and won a scope of work that included the installation of the mooring system, the spar and the topsides; a small amount of hook-up support; and the installation of flow-lines and steel catenary risers (SCRs) for all the lines. 

 

The spar concept is the oil companies' preferred concept to employ nowadays for large deep-water fields to bring the oil to the surface. The spar for Diana, a huge cylindrical floating platform, 705 ft tall with a diameter of 122ft, with a deep keel, takes nearly 700 feet of the water depth and is moored to the sea bed nearly 4,800 ft below. It has about 18,000 tons of topsides on it to process the oil and gas. 

 

Tying the export lines and flowlines to the spar is an important piece of work, which the J-lay system is particularly good at. The lines are freely suspended (they are behaving like a chain and they are named Steel Catenary Riser, for short SCR) in 4,800 ft of water and remain in catenary for 25 years in very strong currents. 

 

To do this whole scope of work the Saipem 7000 substitutes three or four best-in-class dynamically positioned (DP) vessels. In fact there are portions of the work, such as the topsides and SCRs, which no other vessel can currently perform. 

 

From a contractual point of view, it was difficult to formulate a proposal in 1997, not only because the Diana Hoover facilities still had to be designed, but because Saipem was to use new equipment and methods: in particular, the new J-lay system still had to be developed.  

 

“We had to think hard about how best to exploit the opportunity Exxon Mobil was giving us”, says Mr. O’Donnell. “We decided that it was necessary to develop a strategic relationship with Exxon, based on Saipem’s recognition of Exxon’s competence to design the facilities and Exxon’s confidence in Saipem’s ability to do the job when it had to be done, and in particular to complete the J-lay investment. The contract was essentially trust based: agreed schedules, no penalties, no standby rates, etc”. 

 

The fundamental mechanisms created to underpin the strategic relationship were an integrated project team based in Houston; a steering team of executives from Exxon and Saipem; and a novel contracting mechanism based on productivities. 

 

“Bear in mind we were assuming productivities in totally new conditions, with new methods and equipment still to be developed”, says Mr. O’Donnell. “Now at the end of the job, we are very much in line with our targets.” 

 

The steering team met periodically to review the project status as presented by the integrated project team in terms of six key success factors: safety and the environment; cost; schedule; quality; project risk: and the vital factor supporting them all, relationships. “It’s fair to say the job has been a success in terms of all these key issues,” says Mr. O’Donnell. “Perhaps even more importantly, the basis has been created for significant improvement in the future. 

 

“When we think of the S7000, we have an image of a large, very sophisticated vessel. Actually the people are far more important; and this has been demonstrated time and again during both the preparation and the execution of the work,” he continues.  

 

"Notwithstanding the huge enthusiasm for the technological achievements on Diana Hoover, the fact that there were no lost time incidents in over 750,000 man hours of offshore work, in such a new and challenging theatre, is what Exxon and Saipem are most proud of."  

 

The offshore phase took six months, starting in October last year and finishing at the end of April. “Clients want to do things quickly,” says Mr. O’Donnell. “Since with the S7000 you don’t have to mob and de-mob three or four vessels you save time and money. And the fact that we were installing the flowlines and the SCRs when the platform was being commissioned also saved a lot of time.” 

 

The main difficulties and lessons learned concerned increases in suspended weight and hydrostatic pressure; flow assurance in deep cold water, currents and slopes, and remoteness. The impact of these factors on both design and execution is immense. 

 

“Things get extremely heavy. Take the mooring system, for example. Exxon have a famous photograph of the mooring system and the spar. The spar, moored in position, would cover the whole of the Central Business District in Houston.  

Each leg of the 12 leg mooring system is 2.4 km long (a single link of the chain is as big as you are and a lot heavier!).  

 

When the design started, using the Saipem 7000 for the mooring system seemed like “overkill”; when it was finished, we were glad the S7000 was the chosen vessel. 

 

Another example is the impact of currents which are very strong in the Gulf of Mexico. "A phenomenon called an eddy/loop current is effectively like a water tornado. You have to maintain position in that kind of situation”, says Mr. O’Donnell. While Diana did not involve slopes, Blue Stream and many future projects will.  

 

The combination of a powerful DP Vessel and J-lay is crucial in meeting these challenges. “The ability to manage (i.e. lay down and recover, monitor and repair) large pipelines in deep/ultra-deep water requires enormous power and considerable technology. A lot of this technology is vested in our sub-sea company, Sonsub, whose new Innovator ROV performed really well on Diana". 

 

Deep and ultra-deep water jobs are almost by definition in remote locations. Heavy module installation to minimize hook-up and a large capacity vessel are very important in this respect. 

 

In what sense is the Diana Hoover a milestone project? “Everybody is focusing on deep water, and we can certainly say Diana is the deepwater job of the year,” Mr. O’Donnell replies. “The North Sea market is mature and we needed to develop alternatives.  

 

However, since the North Sea is not dead, it is preferable to develop markets that don’t conflict with the North Sea summer season. Diana Hoover is a high-profile project in the key Gulf of Mexico deepwater market, at the right time of the year. 

 

“A ‘holy grail’ in any industry is ‘synergy’. On Diana we have almost ideal synergy between Saipem’s heavy lift and pipelay competencies. Of course in many ways the key to all of this is the S7000 vessel. Now that the new J-lay system has been incorporated, it is particularly suitable for large projects in deep (up to 1,500m) and ultra-deep (up to 3,000m) water." 

 

The decision taken in mid-1997 to invest in the J-lay system took courage and foresight. Now it appears likely that this foresight will be rewarded. In principle there are two major new types of opportunity which the upgraded S7000 can now tackle. The first, normally with the oil majors, is the large integrated project like Diana.  

 

Several appear to be in preparation in the Gulf of Mexico, West Africa and Brazil. The second is gas transportation through deep water: Blue Stream is the first example but there are others: Egypt to Turkey, the UAE to India.  

 

“Wherever you see stranded gas – gas that’s separated from its nearest natural logistical market by deep water - we also see an opportunity to install a deep-water pipeline, and there are a lot of potential routes through ultra-deep water” says Mr. O’Donnell.  

 

“At the moment, the only way to bring stranded gas to the nearest population center is to liquefy it, ship it and re-gasify it. That’s extremely expensive. It’s much safer and cheaper and more environmentally responsible to pipe the gas through a deep-water pipeline. 

 

“The more conventional projects, e.g. the North Sea, Large Abandonment Project, still exist and are still very much in focus,” says Mr. O’Donnell. “Because the future opportunities will be in even deeper water than Diana, the S7000 J-Lay System was purposely ‘over-designed’.  

 

Blue Stream in 2,100m is truly an ultra-deep water project, and the Blue Stream plus Diana capability essentially sets Saipem up to be able to tackle most of what can come up in deep/ultra-deep water in the medium term.” 

 

While Saipem had been studying deepwater pipelay and integrated projects using the S7000 for some years, and were confident of its potential, Diana was the ‘trigger’ which effectively started Saipem on this new path. It was, as Stefano Cao said, “a turning point”. 

Marie Terese Lams 

Source:E.N.I. 

© 2000 Mena Report (www.menareport.com)

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