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One step at a time for gas hydrates DOE and BP evaluating sites for production test while ConocoPhillips starts its North Slope research for using carbon dioxide Alan Bailey Petroleum News
Following success with the Mount Elbert gas hydrate stratigraphic test well on Alaska’s North Slope in 2007, the U.S. Department of Energy and BP are working on plans for a first-of-its-kind, long-term gas hydrate production test, Brent Sheets, regional manager for the Energy Department’s National Energy Technology Laboratory Arctic Energy Office in Fairbanks, told a meeting of the Alaska Support Industry Alliance on Jan. 8.
BP, ASRC Energy Services, Ryder Scott Co., the U.S. Geological Survey, the U.S. Department of Energy, the University of Alaska Fairbanks and the University of Arizona have all been collaborating on the North Slope project.
The project team is evaluating potential sites, prior to site selection for the production test. The team is also investigating the potential to incorporate more partners into the project to help spread the costs, Sheets said.
However, Sheets emphasized that the purpose of the production test would be to add to scientific knowledge about gas hydrates, rather than to jump into maximizing natural gas production.
“This production test would be to maximize the science,” Sheets said. “We’re not really after maximizing the production right now. … We want to build in flexibility so that they can test various production methods and see which ones are going to work.”
ConocoPhillips project DOE is also involved in a new ConocoPhillips project to test the possibility of producing natural gas from North Slope gas hydrates using carbon dioxide.
Gas hydrate (or more correctly “methane hydrate”) consists of a white crystalline substance that concentrates natural gas by trapping methane molecules inside a lattice of water molecules (methane is the primary component of natural gas). The hydrate crystals remain stable within a certain range of temperature and pressure. But when decomposed the crystals yield about 164 times their volume in methane, so that the hydrates constitute a highly effective way of storing natural gas resources.
In the case of the ConocoPhillips project, the company wants to try injecting carbon dioxide into the hydrates, to replace methane with carbon dioxide in the hydrate lattice without altering the hydrate structure. The end result could be a combination of natural gas production and carbon dioxide sequestration.
The project has only just started.
“They’re fully engaged right now in identifying a field site where they might take this to a demonstration point,” Sheets said.
Phase two of the project would involve the development of a plant for field testing and some pre-drill modeling, while phase three would involve drilling, testing and measuring the results, Sheets said.
Barrow gas fields At the west end of the North Slope DOE and the North Slope Borough are investigating the possibility that gas hydrates are contributing to production from gas fields near the city of Barrow.
Although Barrow residents have been heating their homes with gas for decades, production from a couple of wells in the fields has remained at near constant levels, with no pressure degradation or water breakthrough. That phenomenon has led to a theory that gas hydrate disassociation is maintaining the gas pressure in at least one of the fields — Petrotechnical Resources of Alaska has now issued a report that says that there may be a gas hydrate drive in the field reservoir.
“Maybe there’s some disassociation of gas hydrates there and it’s being produced in the free gas reservoir,” Sheets said.
Sheets said that DOE has now given the green light for a second phase of the Barrow project, to enable the design of a monitoring well. The monitoring well would hopefully enable scientists to figure out what is going on in the field reservoir.
Major resource Gas hydrates could form a key component of future energy supplies. According to the U.S. Energy Information Administration the United States currently uses about 22 trillion cubic feet per year of natural gas, and that consumption is expected to increase to about 26 tcf per year by 2030, Sheets said. With just over 200 tcf of current U.S. proven natural gas reserves, the country will need to import or find more gas at some point in the future, he said.
Several government agencies, including DOE, the U.S. Geological Survey, the Minerals Management Service, the Bureau of Land Management, the National Oceanic and Atmospheric Administration and the National Science Foundation are investigating gas hydrates. DOE is the lead agency in the government effort.
“There is this tremendous resource potential,” Sheets said. “The natural gas that occurs in the hydrate form makes this an extremely attractive potential contributor to the energy portfolio.”
Sheets characterized the North Slope gas hydrate deposits as the tip of a pyramid of hydrate resources that might represent as much as 700,000 tcf of natural gas worldwide. Much of that worldwide resource consists of deepwater marine deposits. These marine deposits form the wide base of the hydrate pyramid and would be very challenging to exploit. On the other hand the Arctic on-land deposits at the top of the pyramid, although more modest in size, are much more accessible.
And with the central North Slope hydrate deposits lying under an existing oil and gas infrastructure, DOE has placed a priority on investigating how those hydrates might be developed and safely produced.
“Our focus is getting at the top of this pyramid and understanding this hydrate resource a little bit better,” Sheets said.
But could gas hydrates prove to be a meaningful energy resource?
“If there is this resource there, how are we going to find it?” Sheets asked. “… And if we find it, can we produce it profitably? Can we produce it safely and responsibly?”
Research program The efforts to answer these questions started in the early 2000s, with laboratory experiments on gas hydrates and the modeling of gas hydrate behavior. Much government funding went into developing a cadre of experts in the subject.
“There wasn’t even the body of basic scientific literature when we started all this,” Sheets said.
As part of an emerging scientific discipline, people also expended effort in developing technologies and tools for detecting and characterizing gas hydrate deposits, he said. As a result of this research new seismic techniques have shown great promise in delineating gas hydrates in Arctic onshore deposits.
The 2007 Mount Elbert well provided an opportunity to test both the theoretical modeling of gas hydrate behavior and the emerging detection and characterization technologies. The well targeted and encountered two 50-foot-thick gas hydrate zones, detected from the seismic but otherwise unknown, Sheets said.
A pressure test in the gas hydrates verified the gas hydrate modeling that had previously been done.
“This was the first open-hole extended duration pressure test of a gas hydrate reservoir,” Sheets said.
The project team also successfully recovered gas hydrate core from the well.
“They got some excellent core which was sent out to at least 30 different institutions … for better understanding, educational purposes, research,” Sheets said. “They confirmed the gas hydrate reservoirs. The well performed according to their predictions.”
Another major gas hydrate research breakthrough came in 2008 when the Mallik gas hydrate well in Canada’s Mackenzie River Delta succeeded in producing natural gas for about six days, thus demonstrating the feasibility of continuous gas production.
USGS assessment And in October 2008, following the successful results from the Mount Elbert and Mallik wells, USGS published the first ever assessment of technically recoverable gas hydrates resources — the agency projected 85 tcf of undiscovered, technically recoverable natural gas from North Slope gas hydrates.
“This is really the first time that anyone has come out and said … we think that we can produce methane hydrates to some degree using conventional production technologies,” Sheets said.
However, Sheets stressed that the assessment only considered technically recoverable resources, and did not address the question of whether the hydrates could be produced economically.
Although much of the DOE focus is on the Arctic onshore potential at the top of the gas hydrate pyramid, attention is also moving further down the pyramid. In particular, people are trying to understand offshore gas hydrate resources in the Gulf of Mexico, Sheets said. However, offshore hydrate reservoir quality is not as good as that of onshore reservoirs and the technical challenges of gas hydrate production would be higher than onshore. In addition, reliable techniques are needed for the detection and quantification of offshore hydrates.
DOE has set some milestones for what it wants to achieve in terms of gas hydrate research. The agency wants to see the first long-term production test in the Arctic by 2010, with the scale of economically recoverable resources determined by 2015, Sheets said. The agency also wants to see ground truthing of MMS offshore gas hydrate resource estimates in 2009, he said.
And when it comes to the broader scope of gas hydrate development, DOE wants to foster partnerships with international companies and governments, to encourage people to work together to find ways to bring gas hydrate resources online. In particular, Japan, India, China and Korea are interested in gas hydrate development, Sheets said.
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