Geologists have long speculated that naturally occurring hydrates contain immense volumes of natural gas. But production of gas from gas hydrates under the world’s oceans and in its arctic regions remains uneconomic.
Hydrate experts suggest industry-oriented research during the next several months could yield knowledge crucial to unlocking gas hydrates, whose development is compared with that of coalbed methane-a gas source considered uneconomic 20 years ago.
US Geologic Survey research geologist Timothy S. Collett of Denver acknowledges much remains to be learned about the geologic, engineering, and economic aspects of hydrates-a crystalline combination of gas and water.
Still, he said producing gas from hydrates no longer seems to be a distant goal. This is because gas hydrate energy assessments accelerated during the past 5 years as rising gas prices have stimulated interest in the subject.
“There is a realization that this unconventional resource could be developed in conjunction with conventional gas fields,” said Collett, who recently returned from India, where the USGS was an advisor to the Indian government on hydrate research. India’s objective is production from gas hydrates by 2010.
Various government agencies worldwide and international consortia verified gas hydrate accumulations. Japan, Canada, the US, and India have hydrate research programs (OGJ, Oct. 16, 2006, p. 26). China, South Korea, Norway, Chile, and Mexico are contemplating government-sponsored hydrate research.
Gulf of Mexico
Hydrate expert Arthur H. Johnson of Kenner, La., said research is progressing faster than some people are discarding old misperceptions.
He disputes the notion that the Gulf of Mexico has no significant gas hydrates based on the fact that seismic surveys show few obvious bottom-simulated reflector (BSR) results (OGJ, Apr. 25, 2005, p. 52).
BSRs have been used in many areas to infer the occurrence of gas hydrates.
“It had been said that there is no hydrate beneath the sea floor in the Gulf of Mexico,” Johnson said. “That is wrong. You might not get a good BSR where you have decent reservoir rocks.... The idea of hydrates being just a BSR hunt has gone by the wayside.”
Other seismic indicators suggest substantial volumes of gas hydrates in the gulf’s deepwater upper sediment, said Johnson, chairman and chief executive officer of Hydrate Energy International.
Johnson also serves on the US Department of Energy’s Methane Hydrate Advisory Committee and the American Association of Petroleum Geologists Gas Hydrate Committee.
“We use the term petroleum systems approach to gas hydrates,” Johnson said. “The critical questions that need to be answered involve the ultimate amount of gas that can be recovered from hydrates by each well, the daily production rate of each well, and the expenses involved.”
Chevron Corp. led a Gulf of Mexico joint industry drilling program that drilled two locations 18 months ago, primarily to improve understanding of drilling safety issues related to gas hydrates. Study participants plan more drilling, possibly next year, to assess the commercial potential of gas hydrates.
“Researchers mapped areas where they believe there are sands within the hydrate stability zone that would lead to commercial development,” Johnson said. “The next drilling program would test that model.”
The US Minerals Management Service is conducting a study using a stochastic, or probability-based, methodology to estimate the in-place and technically recoverable gas hydrate energy resource potential for the Outer Continental Shelf (Gulf of Mexico, Pacific, Atlantic, and Alaska).
Preliminary results and the methodology will be released around yearend or early next year, said Pulak K. Ray, MMS Resource Evaluation Division chief geologist.
Alaska
Alaska’s North Slope is another proven exploration target for gas hydrates. BP Exploration (Alaska) Inc. and the DOE are working jointly to characterize North Slope hydrate resource potential within existing industry infrastructure.
The study, in which USGS is a participant, is assessing the commercial viability of gas hydrates in the Milne Point area of northern Alaska.
BP had planned a stratigraphic test for earlier this year in the Eileen gas hydrate trend, but rig delays led to the well’s deferral. The drilling and test program is expected to take 20-25 days and tentatively is scheduled for early 2007.
Both Collett and Johnson suggest that potential US production of gas from hydrates is likely to start in Alaska. Meanwhile, the timing for commercial production of gas from hydrates remains uncertain.
Johnson believes it’s conceivable that commercial production could begin, at least on a limited basis, within 5 years.