Reflecting the overall trends of the industry to go ever-deeper, companies are now attaining first oil through advanced, specialized methods and technologies.
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| GTL FPSO rendering from DSME. |
Companies’ reaches are ever-lengthening, so they can they can close in on and monetize this so-named “stranded” gas through methods such floating GTL (gas-to-liquids).
Floating GTL, or offshore GTL, is a process that allows access to stranded gas. It can also reduce flaring, the practice of which has found itself more and more under the spotlight. OE discusses offshore GTL with CompactGTL and South Korea's Daewoo Shipbuilding & Marine Engineering.
Modular GTL
The modular GTL process begins with associated natural gas and converts it to synthetic gas, or syngas through a steam methane reformer. Fischer–Tropsch reactors convert the syngas to hydrocarbon liquid, explained CompactGTL Business Development Manager Shravan Joshi, saying that the company was addressing “the practical side of things” by applying a modular design to these two fundamental parts of the process into 40ft containerized units. Joshi said that CompactGTL is the only company to thus far get independent approval to commercially deploy a modular GTL solution.
They are generic units that can be mass-produced through Compat GTL’s partnership in Japan with Sumitumo and Kawasaki Heavy Industries.
“We started developing our business model by looking at the problems the upstream industry was having with associated gas offshore. That was the basis on which we started. We didn’t start looking at the most efficient laboratory GTL solution. Our premise was to solve an upstream problem,” he said.
Having worked together since 2008, the British modular GTL specialist formally teamed up with leading floating production storage and offloading (FPSO) unit leader SBM Offshore in 2012 to exclusively cooperate on offshore GTL.
“We figured out really early on we needed a design partner that understood the offshore industry, the FPSO fabrication and manufacturing sides so you could practically put those solutions out to market,” Joshi said.
Brazil’s Petrobras awarded the company a US$45 million contract to build a pilot commercial demonstration plant that, though constructed onshore, was built according to an offshore configuration. The gas feed was from offshore, bringing with it all the contaminants and associated pressure issues, although the facility is aimed at an extended well test vessel.
“Petrobras can play around with the gas compositions – they can add H2S, CO2, ethane, etc. – to test the robustness and reliability of the plant. … In this plant, we’ve demonstrated the ability to convert natural gas from the field into a synthetic crude product that can be blended with mineral crude and then exported out.
“Petrobras didn’t want us to build a plant and then be told you have these engineering risks, these scale-up risks still to contend with. CompactGTL was awarded the contract to eliminate those risks, , going forward to full scale commercial deployment,” Joshi said.
The generic modular units mean that maintenance or issues are less likely to affect the entire train or plant’s production – a problematic reactor module would simply be swapped out with another one.
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| Image from CompactGTL |
As Joshi says, the plant (pictured at right) has “done its job and is no longer operating,” and Petrobras gave approval for full-scale commercial deployment in January 2012, noting that its 20b/d capacity makes it by far the largest small-scale commercial demonstration plant for modular GTL. By comparison, he said that other comparable plants will have 1-5bbl capacity, but still feature “scale-up and engineering risks.”
The project is ready to go into full FEED, but has lately suffered from Petrobras’ tightened budget strings in the last few years in regards to new technology.
Joshi said that one of the most helpful aspects of the company’s partnership with SBM Offshore was that how the partnership has enabled the technology to be easily integrated on the FPSO.
“This is not a bolt on GTL plant – you can’t say, ‘I’ve got a bit of deck space leftover on my FPSO and I’m going to put a GTL plant on there,” he said. “We’ve worked hard with SBM to integrate utilities so you comply with offshore regulations and environmental standards.”
The solution has been approved in principal by a certifying authority.
GTL FPSO
“Big Three” shipbuilder Daewoo Shipbuilding & Marine Engineering announced in late 2012 that it would be building a GTL FPSO, to be completed by June 2016.
H.J. Kim, group leader/senior process engineer in DSME’s Offshore Process Engineering Group, said “sustained, increasing world energy demands, monetization of stranded gas fields, [and] practicable marine application” in proven onshore technology has been the main drivers behind the GTL FPSO.
In addition, “products of the GTL process are clean transportation fuels ranging from diesel to jet fuel that can be readily used in the existing energy infrastructure,” he added.
There are various reasons why that a GTL FPSO was not previously a viable solution offshore, Kim said.
First, he pointed to Syntroleum’s oil GTL FPSO unit, which he said was designed to produce 40,000bo/d and 16,300b/d of GTL products.
“The airblown-reformer technology used in the design resulted in very large equipment throughout the process. For example, the FT reactors were 10m in diameter and required 84-in. pipes,” he explained. “This would present serious challenges in the space-restricted FPSO environment.”
As for Statoil’s GTL FPSO concept, Kim said that it used an autothermal reformer and a slurry FT reactor with a targeted production of 14,500b/d of liquid fuel.
“This concept uses pure oxygen and thus requires an air-separation unit onboard. In addition to the high cost and large footprint of the air-separation unit, the use of pure oxygen poses challenging safety concerns, particularly in the FPSO environment,” he said.
Both companies’ concepts were presented in the mid-2000s, Kim said, which means that “a subsequent examination of [the GTL FPSO option] is warranted because of recent advances in both GTL and FPSO technology.”
Meanwhile, DSME’s GTL FPSO is underway.
“DSME has been recently completed a feasibility study as part of a multi-year R&D program to acquire the basic technology and engineering for GTL FPSO,” Kim said. “This study has utilized technologies that best complied with the needs of the FPSO application. Future work will be directed to develop a more definitive process design and project economics, and will bring commercial realization of this innovative approach of monetizing offshore stranded gas fields.“
Kim and Joshi name Vietnam, Brazil, Australasia and Indonesia as key places where stranded gas is located where a decision for GTL would be driven by the regulator. Joshi said that 10-50 million cu ft/d is the ideal amount for offshore GTL to “play a practical part in getting the associated gas offshore.” Kim said that, for a GTL FPSO, target gas fields are 0.5 - 1Tcf.
“It deals with the economics offshore – offshore GTL only applies to specific scenarios, scenarios where reinjection is going to be very expensive, or piping gas isn’t feasible,” Joshi said.
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