In March 2013, the world’s first offshore production test of methane hydrate was conducted by the Japanese government, using the scientific drillship Chikyu. The target was sand-layer type methane hydrate at the Daini Atsumi Knoll, located between Atsumi Peninsula and Shima Peninsula off the coast of Japan. It was confirmed that methane gas continuously produced from an undersea methane hydrate layer for six days, at an average production volume of 20,000 m3/day (approx. 706,000 cfd).
Not the original plan. As a consequence of Japan’s lack of domestic energy resources and its dependence on imported fuel, energy security and balance-of-trade issues have been overriding concerns for decades.
Japan’s earlier energy paradigm, with nuclear power expected to play an increasing role in addressing energy security and balance-of-trade concerns while reducing carbon emissions, was shattered by the Fukushima Daiichi Nuclear Power Plant accident caused by the Great East Japan Earthquake in 2011. A 2017 paper by Oyama and Masutani, A review of the methane hydrate program in Japan, describes the country’s subsequent efforts to develop this resource.
MH 21. In the late 1970s, offshore seismic data revealed the existence of bottom-simulating reflectors (BSR) in several regions within Japan’s Exclusive Economic Zone (EEZ). A BSR is a line that appears in marine seismic data, which occurs below, and generally parallel to, the seafloor, crossing sediment layers. BSRs indicate a sudden change in seismic impedance, such as when gas-rich sediments exist immediately beneath methane hydrate deposits, due to the geothermal temperature gradient. BSRs are one indicator of the possible existence and depth of a hydrate reservoir.
As evidence of significant methane hydrate reservoirs continued to mount, investigations were conducted to assess the feasibility of producing methane fuel from this potential indigenous energy resource. In 1991, a committee to carry out a research survey of unconventional natural gas was established by the Institute of Applied Energy and other organizations. Since 1993, the sole focus of this survey became natural gas hydrate.
After examining results of the two-dimensional seismic survey performed in the eastern Nankai Trough in 2000, the Review Committee announced Japan’s Methane Hydrate R&D Program in 2001. The MH (methane hydrate) 21 Research Consortium (MH 21) was established in March 2002. Due to an almost complete absence of indigenous, conventional, fossil fuel resources, energy security has been the driving factor behind government support of methane hydrate research in Japan. The MH 21 Research Consortium emerged as a response to this critical priority and was organized specifically to accomplish the exploration and exploitation of methane hydrates offshore Japan.
Second test. A second offshore methane hydrate production test was carried out near the Atsumi/Shima peninsula between April 2017 and June 2017. In June 2017, completion of this test was announced, reporting preliminary values of produced gas of approximately 35,000 m3 for the first production well, over 12 days, and 200,000 m3 for the second production well, over 24 days. A long-term onshore methane hydrate production test on the North Slope of Alaska was planned after FY 2017. Data from this test on extended gas production behavior and the associated problems will be applied to the development of the gas production system for marine methane hydrates. Associated projects led by private companies are expected to commence around FY 2023 to FY 2028, depending on the international energy market and other factors at that time.
It is estimated that approximately 1.1 trillion m3 of original methane hydrate resources exist in the eastern area of the Nankai Trough, offshore from Shizuoka to Wakayama Prefecture. Shallow-type methane hydrate is also known to exist under the Sea of Japan. A three-year study of the resources since 2013 has confirmed 1,742 gas chimney structures where methane hydrate could exist.
A paper titled, Gas production from methane hydrate reservoirs, from the proceedings of the International Conference on Gas Hydrates in Edinburgh, Scotland, in July 2011, describes three types of sub-surface methane hydrate (MH) deposits. These types are: pore filling type MH reservoir; naturally fractured type MH reservoir; and massive/nodule MH deposit. The authors state that among the three types of MH deposits, the pore filling type of MH reservoirs may be promising as energy resources. They are divided further into four groups; Class 1 reservoir underlain by free gas; Class 2 reservoir underlain by free water; Class 3 reservoir confined by impermeable layers; and Class 4 deposits containing MH sparsely in fine grained mud layers. (Kurihara, et. al. 2011)
In the U.S., where abundant shale gas is near many interstate exits, methane hydrate development may seem esoteric and difficult. Perhaps, but in Japan’s case, it’s necessary. The country sees MH as a great opportunity to develop an indigenous energy source. Japan even has a methane hydrate operating company, cleverly named Japan Methane Hydrate Operating Company, established in October 2014, by seven oil and natural gas development companies and four plant engineering companies. The company develops technologies to realize commercial development of methane hydrate.
Economics loom over it all. As Oyama and Masutani point out, “The economic efficiency of fuel gas production from methane hydrate and commercialization was considered to be a prerequisite for the project from the start of MH 21…”
The methane hydrates story isn’t over. Stay tuned…
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