Expectations run high on methane hydrate / Method for efficient, stable extraction of resource from seafloor pivotal for commercialization


Expectations run high on methane hydrate / Method for efficient, stable extraction of resource from seafloor pivotal for commercialization

Tadaaki Inoue and Tomofumi Yonezawa / Yomiuri Shimbun Staff Writers

The success of the nation’s first methane hydrate extraction experiment from the deep seafloor off the coast of Aichi Prefecture is a milestone on the way to commercial production of the resource.

The world’s first extraction of natural gas from the seafloor prompted expectations for production of a purely homegrown energy source. The next task is finding a way to extract gas from methane hydrate in an efficient and stable manner.

The operation was conducted by Japan Oil, Gas and Metals National Corporation (JOGMEC), an independent administrative institution contracted by the Economy, Trade and Industry Ministry. Methane gas was successfully extracted from a well created by the deep-sea drilling vessel Chikyu about 1,000 meters to 1,300 meters below the ocean’s surface.

Methane hydrate, known as “burnable ice,” exists in a solid state in low-temperature, high-pressure environments such as the seafloor and underground permafrost. Reserves of the resource are believed to be distributed across the world. Mainly composed of methane gas and water, the substance is primarily produced by bacterial degradation of organic matter in a low-oxygen environment.

JOGMEC successfully extracted methane gas from underground permafrost in an experiment in Canada in 2007 and 2008. This time the firm applied the same technology at sea, starting drilling from a depth of 1,000 meters below the ocean’s surface. It was able to safely separate methane hydrate into methane gas and water in deep-sea layers of sediment.

This time, the experiment was designed to extract a small amount of methane gas from one well, which would not be a commercially profitable system. The government said it will accelerate efforts to establish the technology necessary for commercial production as early as fiscal 2018, and is expected to include a commercialization target in the new Basic Plan on Ocean Policy, which is currently being compiled.

Methane hydrate reserves in waters around Japan are estimated to be capable of supplying the nation with natural gas for about 100 years, based on current consumption levels. In addition to reserves off the coast of Aichi Prefecture, other reserves have been confirmed in the Sea of Japan, including one off Sado Island, Niigata Prefecture.

If commercial production of methane hydrate is realized, it will contribute to stabilizing Japan’s power supply and may curb the rise in fuel costs due to a surge in imports of fossil fuels.

Economy, Trade and Industry Minister Toshimitsu Mogi spoke about the potential at Tuesday’s press conference after a Cabinet meeting, saying, “We have to overcome the issues one by one to [promptly] utilize resources in the seas around our country.”

Shale gas, a form of natural gas similar to methane hydrate, is mainly contained in a shale strata 2,000 to 3,000 meters underground in North America. Development of shale gas was once believed to be difficult in terms of technology and costs. However, once the horizontal drilling technique was introduced for shale gas reserves in about 2000, development of the resource advanced dramatically, which led to the shale gas revolution.

However, as methane hydrate can only be used after it is broken down into gas and water, extraction of the resource requires complex technology, unlike crude oil that gushes out naturally from the ground. Since methane hydrate exists in high-pressure, low-temperature environments, either the temperature must be raised or the pressure reduced when it is extracted.

“The efficiency of the decompression method has been proven,” according to a Natural Resources and Energy Agency official. The official said the next step must be the development of a profitable digging method and technology to make gas production from the methane hydrate layer more efficient.

(Mar. 14, 2013)

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