|Crews upended the Gulfstar floating spar in February image source: Williams Partners|
Williams' Gulfstar floating production spar (FPS) system is nearly complete, and set to serve Hess' Tubular Bells field in mid-2014. Stephen Whitfield provides an overview of the spar's developmnent.
It has been touted as the future, a job creator a source of vital infrastructural sdevelopment moixed in with some old-fashioned American pride. The technology behind it is not new, but its very existence may prove cruicial to companies lookling for a more efficient direction in mid-sized field development.
Gulfstar is a floating production spar-based system, one of several to come around in the last few decades. Scheduled to launch this year, it should speahead major production for Williams Partners, its creator and owner, and Hess and Chevron, co-partners in Tubular Bells, a field off the New Orleans coastline for which Gulfstar will serve as the central processing facility. The models have been drawn, the parts built, and pieces are almost in place.
And now, nearly three years after its initial commission, the time is near for this thing to show exactly what it can do.
Upon first glance, the partnership between Williams, Hess, and Chevron looks like Gulfstar system nears completion an old fashioned marriage of convenience.
Hess first discovered the Tubular Bells field in 2003, finding reserves in waters ranging from 4300-4600ft on Mississippi Canyon Block 725. Most of the field is now located on MC 726. BP, the company behind the original discovery and subsequent appraisals, sold its stake in the field to Hess and Chevron in 2010. Hess is the controlling partner in Tubular Bells, holding a 57.14% interest. Chevron holds the remaining 42.86% stake.
Williams was brought into the project in October 2011, five months after Tubular Bells had received a letter of award from Hess. In a news release issued at the time, the company said it would handle “production handling, export pipeline, oil and gas gathering and gas processing services” for the project; in other words, it would design the engine that made the whole thing work.
Costing an estimated US$2.3 billion, Tubular Bells was designed in the everpopular “hub and spoke” delivery model. Under this layout, Gulfstar is the hub, the center to which all resources will eventually go. It will be connected to two subsea drill centers, which in turn will be connected to three subsea production wells and two water injection wells.
Gulfstar’s platform was installed at a depth of 4300ft. Its core module has the capacity to produce anywhere from 60,000 to 90,000 bo/d, but Hull expects to yield 120 billion bbl from Tubular Bells, with peak production estimates coming at 40,000 to 45,000 boe/d.
What is Gulfstar?
While new, Gulfstar’s design is firmly rooted in traditional concepts. As the company had no specific offshore location in mind when it conceptualized the system, it had to make it as flexible as possible to adapt to the different logistics of a given site. That all changed after Williams signed on for the Tubular Bells field, thus giving it parameters from which it could build and operate.
Gulfstar is a system with a classic spar hull connected to a three-level topside, with each deck – a main deck, a production deck, and a cellar. The hull was fabricated in an overlapping sequence to speed construction of the module. This design was supposed to speed up the time from the discovery of reserves to first production to about 30 months.
The topside does not feature a rig, only wells based on wet-tree technology: the centerwell, 30-in. diameter, is accessed via a valve tree attached to a well head on the seabed, instead of a riser. It is a more complex design than a conventional dry tree system – since well access is not at the surface, it is harder to access during intervention – but it allows for a lower-cost hull and does not restrict vessel flexibility to the spar.
Gulfstar’s topside has a maximum operating payload of 8600 short tons, three two-phase production separators, and a one-phase test separator, each of which can handle 30,000 bbl of liquid per day (blp/d). Its three T60 power generators each run on a dual fuel configuration and features a waste heat recovery system. It is built to last 25 years and house up to 50 people at any given time. It has a single-piece lift that can handle up to 6600 short tons.
The hull can reach a depth of 8500ft. Its outside diameter is 85ft, and it measures 60ft from the top deck to the waterline. It has two pull tubes that can accommodate export risers as long as 14-in. in diameter, its flowlines consist of eight pull tubes that can accommodate 15K risers up to 8.625-in., and its umbilical/injection lines consist of eight pull-tubes.
Contained within the hull is 10,440 bbl of dry oil, which will help with unexpected well shut-ins. Should that happen, the dry oil can be pumped to the flow lines, taking the place of live crude reserves. Gulfstar has 1160 bbl of methanol and other chemicals like asphaltine and paraffin inhibitors on board as well to help with flow assurance.
A speedy delivery
One of the central tenets of Williams’ vision for Gulfstar was to significantly reduce the time from the discovery of reserves to the first production. The goal is to finish the project in 30 months, which would be sometime this year; initial production has long been slated for mid-2014. So far, things appear to be on schedule. After mooring the floating spar to the ocean floor in February, crews in March lifted and installed Gulfstar’s three-level topside platform.
Williams was able to accomplish this goal by serving as a one-stop shop for everything. Williams funded Gulfstar and the export pipelines itself, essentially cutting out the middleman and creating a consistent set of interfaces within the system, as opposed to the multiple interfaces one would get in dealing with multiple companies.
|Gulfstar's floating spar was towed 135mi. southeast of New Orleans before being moored in about 4000ft. of water in February 2014.|
Another key to reducing the construction time was choosing to build in the US. It is no secret that Gulfstar is the first spar-based FPS whose major components were built in America – the topsides were constructed by Gulf Island Marine Fabrication in Houma, Louisiana, while the hull was constructed at Gulf Island Fabricators in Aransas Pass, Texas. In all, about 90% of the materials for Gulfstar came from the US.
Gulfstar’s American origins undoubtedly provided a boon of good publicity for Williams, as well as a boon to the economy – the project led to an estimated 1000 new jobs in 20 states during the course of its development – but it was also a practical measure. Since both towns are on the Gulf of Mexico, shipping the components to Tubular Bells was a much quicker process to execute than if they had been built overseas.
Gulfstar was also the first spar built on a graving dock, allowing for a simplified load out process. Its deck was lifted as one singular piece during the installation process, which limited the time needed to hook up offshore. The hull blocks were built vertically, thus allowing for better access to the equipment as it’s being installed and reducing the problems that can come with horizontal construction. According to Williams’ video on the system, the vertical blocks were rotated to a horizontal position once completed, after which they were lifted and set into the graving dock for incorporation into the hull.
“Gulfstar provides a complete ‘floating production system to market clearing point’ solution for producers in the Gulf for their oil, gas and liquids production, designed specifically to maximize their net present value and minimize risk,” said Mark Cizek, Williams’ Gulfstar Project Director. “The ‘design one, build many’ construction concept allows for standardized design options and enhanced safety and reliability of each unit. The repeatable concept also increases speed to market.”
In addition to anchor commitments from Tubular Bells owners, Gulfstar executed agreements in January with Gunflint field owners. The Gunflint tieback is designed and engineered with modifications expected to occur after completion of the base Gulfstar project. With hook-up and commissioning activities currently underway, Gulfstar is on schedule to start serving Tubular Bells in 3Q 2014 and Gunflint in 2016.
“Landing this Gunflint tieback before first oil is received from the anchor tenants demonstrates the promise of the Gulfstar model for producers, both economically and technically,” said Rory Miller, senior vice president of Williams’ Atlantic-Gulf operating area. “As a midstream company, Williams is focused on infrastructure solutions of this nature that connect the best supplies with highest-value markets. Gulfstar is one of approximately $4.5 billion in large-scale projects we expect to bring into service in 2014 and 2015.”
Gulfstar could potentially be a model for future developments of mid-sized fields, as companies look to cut down on the time and cost needed to construct offshore systems. Williams hopes to connect it other systems that it owns and operates in the Gulf of Mexico, and it could become a primary facility for other deepwater fields. And perhaps, down the line, there will be other projects like it developed in the Gulf’s waters.