Keeping pace with the deepwater push
  from: Offshore Engineer
  by: Russell McCulley
  Wednesday, March 19, 2008

The inexorable push toward untapped energy resources in the deeper reaches of the Gulf of Mexico’s canyons and folds has created design challenges for both oil and gas exploration companies and those tasked with building the systems that get those products from the source to the shore. Russell McCulley discusses the issues in his opener to this month’s pipeline design, installation and maintenance review.

Strip away the water and sands from the Gulf of Mexico’s Outer Continental Shelf, and you’ll find a vast spider’s web of pipelines – some 28,000 miles of pipe crisscrossing the Gulf from Texas to Alabama. Although deepwater pipelines currently account for a small fraction of the total, that’s where the industry’s focus has been for the past decade. And companies that built their businesses on the installation and maintenance of shallow water pipelines have had to adapt quickly to the trend.

‘Pipeline technology, as far as the equipment itself, has been keeping up with water depths as production keeps going further and further out,’ says Alex Alvarado, chief of the pipeline section in the Gulf of Mexico field operations office at the US Minerals Management Service, the government agency responsible for regulatory oversight of pipeline design, installation and maintenance. ‘Pipeline technology has been able to keep up with that, as far as installation and operation of pipelines at those water depths.’

A handful of deepwater projects have recently come on line or are gearing up for production in the gulf ’s deepwater fields. The Atwater Valley Producers Group’s Independence Hub, which started production in July 2007, currently holds the record for operating pipeline depth in the Gulf, with export lines that reach depths of 7864ft (OE November 2007). It will be rivaled by a joint venture of Chevron and Anadarko in the Blind Faith field, and Shell and partners’ Perdido Norte project in the Alaminos Canyon area, which will include an export line submerged in a record 8250ft of water. Blind Faith is scheduled to begin operations this year and Perdido Norte is scheduled around the turn of the decade, both with pipelines built and owned by The Williams Companies. The $250 million Blind Faith pipeline project includes two 37 mile extensions connecting the field to Williams’ Canyon Chief and Mountaineer pipelines.

‘All of the pipe is now laying on the ocean floor,’ says Rory Miller, vice president of Williams’ Gulf Coast area, midstream division. ‘We’re in the process of putting a connection in place that we did in situ. It was a pretty unique operation.’

The company is building pipelines for Perdido Norte that will operate in up to 9000ft of water, Miller says. The $560 million project is on target, he says, to begin transporting oil and natural gas around the end of the decade. A 107 mile gas export line will be capable of moving 265mmcf/d, and the project’s 77 mile long oil line will have the capacity to carry 150,000b/d to refineries on the Gulf Coast. For Williams and other midstream service and transport companies, adapting to the demands of deepwater exploration and production has been ‘an incremental journey,’ Miller says. ‘They keep stepping out another thousand, two thousand feet, and the technology slowly evolves until you get to the point where you can handle it.’

The pipe itself isn’t radically different from that used in shallower waters, although extreme depths and cold temperatures require that pipes are well insulated and able to withstand great pressure. Cold and pressure make deepwater pipelines more susceptible to the buildup of gas hydrate, paraffin and other substances, which can restrict the flow of crude oil. Insulation to reduce heat loss is the first line of defense; other measures include the continuous injection of flow-enhancing chemicals such as methanol or ethylene glycol through the pipelines and, increasingly, using smart pigs instrumented to detect pipeline corrosion and locate leaks.

Deepwater lines are less vulnerable to the things that often cause damage in shallower waters, especially tropical storms and hurricanes. ‘The deepwater pipelines are pretty well-insulated from storms,’ Miller says. ‘A storm doesn’t penetrate to 5000ft or 6000ft of water depth. The danger there is when something is thrown or lost overboard, where it could land on a pipe, or you can have some kind of extreme excursion on a floating production system that overstresses a riser.’

When damage does occur, however, repairs can be costly and time consuming. Saturation dive repairs can be performed at depths of up to a little more than 1000ft; beyond that, crews must use remotely operated vehicles to detect and diagnose problems and to assist in repairs. Often, a heavily damaged section of line can be cut, removed and brought to the surface. Pipeline collet-style end connectors are installed before the subsea installation of the jumper with a colletstyle connector; diverless collet connectors can also be installed on the sea floor using ROVs. If the damage is minor and the pipeline has not been severed, repair crews will often use ROVs to install diverless clamp connectors.

ROV technology is increasingly being used to maintain and repair pipelines in shallower depths, eliminating the lengthy decompression process required to bring divers back to the surface — a full day, roughly, for every 100ft of water depth. ‘The technology is catching up,’ says Mike Willis, Global Industries’ senior director of diving for the Gulf of Mexico region. ‘They can go out with ROVs instead of using divers at those depths.’ Along with cost savings, he says, ‘the safety factor is huge. Any time you can send a piece of machinery down and not have a human down there in harm’s way, you have to take advantage of that situation. You never want to put anybody in harm’s way if you don’t have to.’

New deepwater pipelines are designed to last 40 years or more, and despite the fact that the lines are submerged in what Miller describes as ‘extreme environments’, engineers expect them to develop few problems over time. ‘A pipeline laying on the ocean floor in 6000ft of water, with no span, it’s probably going to be in pretty good shape,’ he says. ‘There’s no oxygen there, it’s very cold — a lot of things that would typically cause you problems don’t exist down there.’

The biggest challenges for deepwater pipeline systems, perhaps, arise during installation. The terrain at such depths can be rugged, and operators must find routes that minimize ‘spanning,’ or long stretches of unsupported pipeline, which can cause the pipe to bend. There are environmental concerns as well, including the possible disturbance of chemosynthetic communities – organisms such as tubeworms and mussels that live on hydrocarbon seeps on the Gulf floor. And the weight of insulated pipeline and the depths to which they are lowered require specially equipped construction vessels.

‘The incremental step-out in water depth usually makes the design challenges manageable,’ says John Stearns, vice president of marine pipeline systems for Intec Engineering. ‘However, we are not only seeing increases in water depth, but also substantial increases in pipeline diameter that present ever greater installation challenges. One of the most significant issues is top tension capacity for the current generation of lay vessels. Combined increased water depth and diameters can in some cases mean there are only one or two vessels available in today’s market that can install some of the projects that are currently on the horizon.

‘The pipe at those depths is probably an inch thick or more on the wall thickness, and if you’ve got something that heavy hanging off your boat – you might have over a couple of miles of pipe hanging off your boat – that’s a huge load,’ Miller says. ‘Just the tensions that you have to be able to handle on the vessels – seems like every year these guys are modifying the vessels. They just get bigger and bigger.’

New vessels are coming into service in the Gulf of Mexico for both installation and maintenance of deepwater pipelines. In 2010, Global Industries plans to launch the Global 1200, a 532ft multipurpose construction vessel capable of handling up to 60in concrete-coated pipe and outfitted with a 1200t capacity crane. It will join a fleet augmented by two new dive support vessels: the REM Fortress and the REM Commander, which recently installed a deepwater jumper for Williams’ Blind Faith project and, like the Fortress, has the ability to lower items in water as deep as 12,000ft. This summer, the company will introduce the Olympic Challenger, a DP2 multi-service vessel designed for inspection, maintenance and repair work on subsea umbilicals, risers and flowlines (Surf) and equipped with two ultra heavy duty, 200hp ROVs — the first in Global’s fleet — as well as a 250t capacity crane and two moonpools.

The new acquisitions are part of the company’s ramped-up focus on deepwater projects (OE October 2007). BK Chin, who took over as CEO in October 2006, plans to double Global’s revenues from $1 billion to $2 billion over the next few years, with deepwater services providing the bulk of that growth. ‘That’s really where the emerging markets and the future of oil and gas are going,’ says Willis. ‘We’ve always had deepwater capabilities. What we’re doing now is expanding our deepwater capabilities to a level that is world-class, and at a level that is going to be able to provide services anywhere in the world.’

Closer to shore, pipeline operators are still coping with the damage wrought by a series of powerful Atlantic hurricanes, most notably 2005’s Katrina and Rita, which created storm surges that tossed around pipelines resting as far as 200ft below the surface and moved some as far as 5000ft from where they were installed.

‘These two storms, from my experience, did the most damage that we have ever seen before,’ says Alvarado, of the Minerals Management Service. ‘There was extensive damage, and one thing we saw that we haven’t seen before is the amount of pipelines that were moved as a result of the storms.’

While most of the agency’s post-2005 regulation revisions have focused on platform construction, the MMS recently issued a proposed set of guidelines that seek to modernize regulations of pipelines and their right-of-ways on the Outer Continental Shelf. ‘We need to update the models with the new metocean data so that we can see what changes need to be made to design for the stability of pipelines,’ Alvarado says. ‘The focus right now has been on updating the metocean data for platform design.We are emphasizing to industry that we need to do the same thing for pipelines.’

The agency extended the public comment period to mid-March, from an original deadline of 31 January 2008. One potentially contentious element of the proposed rules is a provision that would require companies to have an integrity management program, Alvarado says – a measure that some worry will create extra burdens, but that many larger operators already have in place.

‘Offshore pipeline compliance is a huge effort for us,’ says Miller. ‘All of these facilities are in pretty extreme environments. So if you’re looking from a standpoint where you want to be in business out there for 40 years with our assets, it’s important to have an industryleading integrity approach.’ OE

Ready for repairs

Deepwater pipeline repairs can be costly, both in the actual work and the lead time – in many cases, more than a year – required to obtain the proper equipment and effect repairs.

Last year, pipeline operators Enterprise Products Partners and Enbridge joined BP Exploration & Production and Eni to form the Deepwater Response to Underwater Pipeline Emergencies (DW RUPE), a cooperative endeavor designed to speed repairs of pipeline systems in up to 10,000ft of water.

The agreement calls for $12 million in repair equipment such as diverless clamps and other connecters to be stored at an easily accessible site in the Houston area. Modeled on a 30 year-old shallow water RUPE that has some 30 co-owners, DW RUPE is expected to sign on more operators once the program is up and running this year.

‘The program is proceeding, and we’re still on target’ for a 2008 launch, says Mike Stark, director of offshore pipelines for Enterprise and chairman of DW RUPE.

In the meantime, Tulsa-based Williams Companies is scheduled to begin construction this month on a facility to house the company’s own pipeline emergency repair kit, or PERK, in Ragley, Louisiana, near Lake Charles. The system will allow the company to conduct repairs on 12in to 18in diameter pipelines at depths of up to 10,000ft.

The kit includes diverless clamp connectors for surface or subsea repairs and diverless mechanical pipe connectors, and has been tested on the company’s ongoing project connecting the Chevron-Kerr McGee Blind Faith field pipeline system to existing pipelines in the Devils Tower field.

‘While it is rare that we experience problems with deepwater pipelines, in the event of a hurricane, anchor drag, equipment drop, leaks or other emergencies, we will be positioned with the equipment, technology and proven installation methodologies to make needed repairs and resume flow quicker than anyone in the industry,’ the company said in a statement.

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