News & Information 2009

March 5, 2009

Successful Experiment Involving Methane Hydrate Gas Recovery at Lake BaikalA Major Step Toward Establishing New Methane Hydrate Gas Recovery Technologies

Shimizu Corporation (president: Yoichi Miyamoto) has successfully demonstrated an experiment for dissociating and recovering gas from methane hydrate in near-surface sediments at the bottom of Lake Baikal at depths of approximately 400 meters. As a joint effort involving the Limnological Institute of the Russian Academy of Sciences, the Kitami Institute of Technology, and Hokkaido University, this experiment marks a major step toward establishing the technologies needed to recover gas from near-surface methane hydrate. Shimizu plans to perform surveys of surface deposits of various resources and to work to improve plant equipment to achieve higher recovery efficiency and cost savings, with the goal of establishing the technology within four years.

This experiment was commissioned as part of the Research Program on Development of Innovative Technology initiated by the Japan Science and Technology Agency in fiscal 2006.

Methane hydrate (hereafter referred to as "MH") has drawn significant interest as a next-generation energy resource and alternative to petroleum. A natural gas component, methane, is trapped in MH, which is often found under the floor of seas or lakes under low-temperature, high-pressure conditions. Since MH is known to exist in abundance in deep layers 100 to 300 meters below the sea bed and in similar locations, most projects seeking to collect MH tap reserves located in deep layers. However, in recent surveys and research, MH has also been detected in the near-surface layer of sea beds and lake bottoms. Around Japan, for example, MH reserves have been confirmed in the near-surface layers of sea beds in the Sea of Okhotsk and the Sea of Japan.

As the phase equilibrium state of deep-layer MH is upset by slight changes in temperature or pressure, the gas can therefore be dissociated and recovered by heating or depressurizing. However, since near-surface MH is located closer to the surface of the sea bottom, it exists in a more stable state than deep MH. This called for a new, innovative method for disturbing the stable condition of near-surface MH to permit efficient gas recovery.

In August 2008, gas was successfully recovered at depths of some 400 meters in the southern lake basin of Lake Baikal. In this experiment, MH and water were agitated in a cylindrical reaction container (diameter: 1.2 m, height: 2.0 m, weight: approx. 840 kg) made of steel (known simply as a "chamber"). MH dissolved in water was then brought to the surface of the lake for gas dissociation and recovery. This simple but unique gas recovery method resulted in a successful experimental outcome. The innovative method adopted involved the simple agitation of MH and water, rather than heating or depressurizing MH. This marked the world's first experiment in which gas was successfully dissociated and recovered from near-surface MH occurring at a sea or lake bottom. The success of this experiment may prove significant for Japan's resource development, since it demonstrates the possibility of tapping vital resources buried in the beds of seas and lakes.

< Overview of Gas Recovery Technology Used in the Experiment >

Overview of Technology

A steel cylindrical chamber with 32 water jet nozzles (16 horizontal and 16 vertical) installed inside was placed on a lake bottom. The bottom of the chamber was open to allow the chamber to fill with lake water. Jets of water were applied to excavate and agitate the MH layer within the near-surface layer of the lake bed, dissolving MH into the water, which was then pumped to the lake surface. The lower water pressure closer to the lake surface resulted in the separation of the gas from water. The separated gas was then recovered.
Overview of Experiment and Results

The experiment was carried out at Lake Baikal over 10 days by 12 researchers (nine Japanese and three Russians) and 12 crew members onboard the G. Yu. Vereshchagin, a research vessel displacing 360 tons and owned by the Limnological Institute of the Russian Academy of Sciences.
Hydrocarbon gases such as methane and ethane accounted for 90% of the gas recovered after approximately 100 minutes of agitation. The gas composition and characteristics were close to those of dissociated MH gas.
Technical Features
- The new technology can be used to dissociate and recover gas without changing the temperature or pressure of the water surrounding the MH.
- MH dissociation occurs only within the chamber positioned at the lake bottom. No methane is generated outside this chamber.

With an eye toward MH resource development engineering, we plan to continue performing surveys of near-surface resources and improving plant equipment to establish technologies capable of playing key roles in resource development.

< References >

Shimizu's Goal in Pursuing Technologies for Gas Recovery from Near-Surface MH

The primary target of Japan's MH resource development plan is undoubtedly the huge MH reserves located deep under the sea bed of the Eastern Nankai Trough. However, exploring MH resources in the near-surface layer of the sea bed also represents a promising option for securing a more stable energy supply. Shimizu is pursuing technologies aimed at establishing a safe, cost-effective method for gas recovery.
Processes Leading to Success

Shimizu began planning this experiment in 2005, selecting Lake Baikal as a pilot site for an international joint research project.
In preliminary surveys, we studied the sedimentary soil of the lake bed and the methane hydrate characteristics through geophysical exploration and core sampling. We also examined the topography and lake bed conditions near the experiment site in a survey conducted with a manned submersible vessel.
Survey Using a Manned Submersible Vessel

The MIR 2 manned submersible vessel owned by the Russian Academy of Sciences was used for the submersible survey. Able to descend to depths of 6,000 m, the MIR 2 accommodates one pilot and two observers.
During the survey, the MIR 2 operated underwater for eight hours to examine the topography and lake bed conditions at the location selected for the experiment site. A dedicated instrument for the cone penetration test developed by Shimizu was attached to the manipulator and used to check the strength of the surface layer of the lake bed. The manipulator, a mechanical hand that operates much like a human hand, is often used in submersible research work conducted at ocean depths.