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Questions Cloud Hydrate Potential

But Pockets of Activity Possible

The resource known as gas or methane hydrates, which lies frozen in combustible ice crystals below the ocean floor -- or closer to the surface in the Arctic regions -- has been estimated to represent double the energy potential of all of the world's conventional oil, gas and coal reserves combined.

That is a potential that has many geoscientists and industry companies anxious about the future -- and with good reason.

But Timothy S. Collett, a research geologist for the U.S. Geological Survey, Denver, who has been involved in the research of gas hydrates for the past 20 years, sees the question marks that accompany the potential.

Collett, who delivered a paper on the subject at last year's AAPG Wallace C. Pratt Memorial Conference on Petroleum Provinces in the 21st Century, believes that along with the vast possibilities, there are considerable uncertainties.

For starters, Collett lists three main issues.

♦   There are hazards involved.

Typically, when a conventional drilling installation is set up on the ocean floor that will drill through the hydrate crystals, the gas can become separated from the water, causing an explosion. Also, this separation can upset the solidity of the sediment on the ocean floor, creating a landslide effect.

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The resource known as gas or methane hydrates, which lies frozen in combustible ice crystals below the ocean floor -- or closer to the surface in the Arctic regions -- has been estimated to represent double the energy potential of all of the world's conventional oil, gas and coal reserves combined.

That is a potential that has many geoscientists and industry companies anxious about the future -- and with good reason.

But Timothy S. Collett, a research geologist for the U.S. Geological Survey, Denver, who has been involved in the research of gas hydrates for the past 20 years, sees the question marks that accompany the potential.

Collett, who delivered a paper on the subject at last year's AAPG Wallace C. Pratt Memorial Conference on Petroleum Provinces in the 21st Century, believes that along with the vast possibilities, there are considerable uncertainties.

For starters, Collett lists three main issues.

♦   There are hazards involved.

Typically, when a conventional drilling installation is set up on the ocean floor that will drill through the hydrate crystals, the gas can become separated from the water, causing an explosion. Also, this separation can upset the solidity of the sediment on the ocean floor, creating a landslide effect.

The latter is not a danger on Arctic land surfaces, but the explosion danger is there.

♦  It is not yet clear whether these methane gases can be harvested in an environmentally safe way without contributing to the greenhouse effect, or destabilizing continental margins, possibly triggering undersea landslides and potentially cataclysmic tsunami waves.

Some experts point to evidence that massive, naturally occurring releases of these gases in the past contributed to abrupt changes in the earth's climate, as well as towering tsunami waves like one that wreaked havoc in northern Europe 8,000 years ago.

♦   The harnessing of these gases as an energy resource is a difficult proposition, although, in this issue, real progress has been made.

Collett said that since the 1970s the Ocean Drilling Program (ODP) and its parent Deep Sea Drilling Program (DSDP) have acquired a significant number of samples of direct geologic data relating to these hydrates. These explorations have been scientific, and dealt with issues such as plate movements and climate changes regarding these hydrates.

"Basically, these hydrates have been revealed to exist around the ocean margins of the world," Collett said. "However, many occur within clay dominated rock sequences, which would not be considered as a conventional reservoir."

Collett adds that there are often low concentrations of this gas, though they are distributed over a broad area.

On the other hand, highly concentrated quantities of this gas have been discovered within conventional reservoir routes in the Arctic, specifically in the west Siberian basin of Russia, the McKenzie River Delta in Canada and on the North Slope in Alaska.

Accidents and Intentional Lessons

In the late 1960s and early 1970s, Russians drilling in the Messoyakha field in northeast Siberia discovered this gas by accident.

The Russians were drilling for conventional gases, which were underlain by the hydrate gases. The drilling changed the pressure of the reservoir, releasing the underlying gases, producing a bonanza that hadn't been anticipated.

It was only afterwards, in noting the changes in the reservoir pressure, that the Russians concluded the existence of the hydrate gases. The nature of the findings, however, was not particularly helpful for future research.

A more intentional -- and more valuable -- effort in terms of measurable results was made in 1998 by the Japanese National Oil Corp. and Geological Survey of Canada in McKenzie, in the Mallik 2L-38 gas hydrate research well.

The results of this venture (published in the 1999 Geological Survey of Canada Bulletin 544) confirmed both the existence of the hydrates and the viability of the engineering technology designed to harness the same.

Partnerships are now being formed for actual drilling in 2002. The USGS and Department of Energy will be involved as secondary partners, along with others. In fact, in 1993, Collett published through the USGS an AAPG article reviewing the distribution of gas hydrates around the Prudhoe Bay oil fields.

"From this study," Collett said, "I concluded that the Prudhoe Bay field may contain as much as 45 trillion feet of gas."

There When You Need It?

The driving force in these endeavors, however, is the Japanese National Oil Corp., in partnership with its government. Japan has been engaged in the Mallik venture mainly to learn what it could for its more immediate project in the Nanakai Trough, just off of the southeast coast of Japan.

The reason is clear.

"Japan imports 98 percent of its energy resources," Collett said, "so that country has the motivation to spend much more time and money in making gas hydrates a viable source of energy."

Collett adds that, in terms of gas hydrates, the Mallik and Nanakai wells are geologically very similar.

The United States, however, doesn't face a similar urgency, and Collett doesn't see the existing structure for energy exploration being challenged soon.

"I don't believe there will be a rush to market the gas hydrates," Collett said. "I don't think there will be a significant offshore interest in marine gas hydrates for 30 or more years.

"However, in very localized areas, such as the North Slope in Alaska, I believe there may be some real domestic activity within the next 10 years or so."

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