Weathering the storms
  from: Offshore Engineer
  by: Jennifer Pallanich
  Tuesday, July 08, 2008

Even in the days of plenty, a number of factors can push a field into the marginal category: low production rates, short field life, and high costs of field development or abandonment. Jennifer Pallanich reports on a start-up company working to bring back focus to the shallow water minimum facilities platform in regions with severe storms.

Over the past few years, the ‘downers’ left in the wake of hurricanes Katrina and Rita have garnered a lot of attention in the Gulf of Mexico. Less widely publicized, however, have been the offshore structures that stood in the path of these storms and escaped relatively unscathed.

One shallow water design that seems to have fared remarkably well is the minimum facilities guyed caisson installation known as the Tarpon. The design traces its genealogy from American Oilfield Divers in the 1980s and later became the property of offshore contractor Stolt (now Acergy). Seeking to extend its application base beyond the Gulf of Mexico, Acergy installed a number of such units in Southeast Asia.

In May this year the rights to the patented Tarpon system were acquired from Acergy for an undisclosed sum by Tarpon Systems International (TSI), an affiliate of Houston-based construction and decommissioning management company JAB Energy Solutions formed at the beginning of 2008. JAB cut its teeth on a rigless subsea well abandonment job for Nippon and is now handling a $27 million Gulf of Mexico abandonment project as well as working on a Tarpon system for installation for a US-based operator off Malaysia.

In the Gulf of Mexico, things went a little quiet on the Tarpon marketing front during Acergy’s tenure. But Brent Boudreaux, one of the founders of JAB Energy Solutions and a partner in sister company TSI, is now looking to redress the balance, maintaining that the design’s record of performance on marginal fields in the hurricane-prone Gulf speaks for itself.

Designed to API RP-2A 1st edition, API bulletin 2INT-DG and API bulletin 2INTMET, the Tarpon system offers a high level of structural integrity in the face of 100- year storms, Boudreaux says, pointing out that the 19 units in the path of hurricanes Katrina and Rita withstood the wind and waves without catastrophic damage. ‘We picked up none of these (19 platforms), and they are all producing today, or could be’ if production levels in two fields had made repairs worthwhile, he adds.

Some platforms sustained deck damage, he acknowledges, while two sustained minor structural damage. In one instance, in High Island block A-467, the platform was leaning at about 4° after its cables loosened. ‘It didn’t fall over,’ he notes. ‘Had the production been good, [the operator] would have been back on production for a few hundred thousand dollars.’ Instead, based on low production levels, the operator opted to P&A the well.

Boudreaux says the design’s 100% redundancy with two steel cables on each of three sides kept the unit upright in the face of the hurricanes.

‘What saved it from the hurricanes is it’s flexible,’ he says.

A Tarpon system in Main Pass block 141 bent just above the termination clamp about 40ft below the water surface. It sustained a direct hit by Hurricane Ivan without damage, Boudreaux says, but ‘Katrina hit it and bent it above the termination clamp’.

While the system could have been repaired, depleted reserves prompted the operator to P&A the well and hire JAB Energy Solutions to manage the Tarpon salvage operation so the deck could be reused.

Further, Boudreaux says the Tarpon is one viable solution for offshore wind farms, now being given serious consideration in a Gulf of Mexico context. The simplicity of the design coupled with the flexibility of the installation process give a host of options not found in other designs, he argues. Offshore wind energy is current marginal field development at best so the economics behind the Tarpon design should make it attractive, he adds.

According to Boudreaux, the Tarpon is profitable at $30/bbl oil. It can handle eight wells producing 30mmcf/d and typically supports 100 tons to 250 tons of deck load. In special circumstances in benign environments, the design can be engineered to handle up to 450 tons of deck weight. It is most often suitable as an unmanned minimum facilities structure for 80-220ft water depth, but this can be extended to 350ft.

Boudreaux says the unit shines in depths exceeding 180ft when compared to brace caissons and tripods, because of its functionality, lower manufacturing and installation costs and faster delivery times – 20 weeks from start of fabrication to delivery. While a full-fledged tripod may provide extra functionality, he says, it’s often more expensive.

‘It’s all about production. It’s all about how much equipment you need on the deck,’ Boudreaux says, noting TSI is not opposed to doing turnkey contracts with the system.

Because of the simple construction and easy installation, the company sees the design as a low capital expense solution which can additionally be used as an early production facility. Maintenance and abandonment costs are low, and at the end of field life it can be recovered and reused.

In the two decades or so that the design has been around, there have been some improvements, with the most recent being the new termination clamp assembly. Boudreaux says the new design requires more steel but saves a day of derrick barge installation. Typically, he says, a Tarpon takes four to seven days to install, depending on the water depth. It often takes about five days to remove.

Steel is no longer the long-lead item, observes Boudreaux. ‘Our long-lead items today are the guy wires.’

Tarpon Systems International plans to begin stocking guy wires to cut down on that delay, he adds.OE

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