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Agency for Natural Resources and Energy ANRE Estimated the Amount of Shallow Methane Hydrate Resources and Verified the Estimation Results

The Agency for Natural Resources and Energy (ANRE) conducted surveys in order to ascertain the amount of shallow methane hydrate resources from FY2013 to FY2015 based on the Basic Plan on Ocean Policy.

The National Institute of Advanced Industrial Science and Technology (AIST), an organization to which ANRE commissioned this project, estimated the amount of shallow methane hydrate resources targeting one gas chimney structure offshore the Joetsu region and found as a result that approximately 600 million shallow methane hydrate in cubic meters are estimated to lie in the structure in methane gas equivalents.

In response, a committee of external experts examined the estimation results and opined that they were derived from adequate methods of estimation and that they should be interpreted within a certain range of variation.

1. Introduction

Methane hydrates present in Japan’s waters can be categorized as either the shallow-type or pore-filling sand-layer type. From FY2013 to FY2015, based on the Basic Plan on Ocean Policy, which was approved by the Cabinet in April 2013, ANRE established exploration and resource assessment surveys focusing on shallow-type methane hydrates which had been previously discovered in the Sea of Japan.

As a result of this exploration, ANRE found that 1,742 gas chimney structures, at which shallow methane hydrate resources are expected to be distributed, lie in the waters around Japan. In addition, through seabed drilling, it also succeeded in direct measurement of the property inside the gas chimney structures, and analyzed and examined chemical components of pore water in the strata and other elements based on the gained geological samples (see press releases on December 25, 2014, and on January 22, 2016).

Based on the data from these surveys, AIST, an organization to which ANRE commissioned this project, compiled the estimated amount of shallow methane hydrate resources. Following this, the committee of external experts verified the estimation results and other data.

2. Estimation results concerning the resource amount calculated by AIST

1) Target of the estimation

In the process of advancing a variety of surveys, it was found that the distribution of methane hydrate inside the gas chimney structures is discontinuous, making the range of the distribution difficult to estimate, and also that the inside of the structures varies by the structure. To address this situation, AIST decided to reduce the range of estimation targets for surveys from entire waterways to certain areas. Specifically, it decided to estimate the amount of resources in a mound terrain having the gas chimney structure at the mid-western section of the Umitaka spur (hereinafter referred to as the “Umitaka mound structure”; in the area with a size of approximately 200m x 250m with the depth of approximately 120m; see also the figure at the end of this press release) offshore the Joetsu region, since a large amount of data on this area had already been collected through surveys and since aggregated methane hydrate was already found there, an area where a variety of academic research was most advanced at the time period before FY2013.

2) Estimation methods

AIST mainly adopted three types of estimation methods. First, it adopted a logging-while-drilling (LWD) method in which estimation is conducted based on the data on geological properties, e.g., hardness, electric resistance, and geological porosity, which were measured simultaneously using a measuring machine mounted on a seabed drilling machine (number of drillings: eight).

Second, it adopted a core analysis method in which geological sample cores are collected while drilling the seabed, and estimation is conducted based on the density of chemical components of methane hydrate and pore water contained in the samples (number of drillings: six). AIST combined the data collected at the surveys and estimated the distribution of methane hydrate.

Third, AIST also estimated the volume of the resource in the range of distribution of methane hydrate having strong electric resistance, using a marine controlled source electromagnetic method in which estimation is conducted based on the three-dimensional distribution of regions with electric resistance beneath the seabed, measured by artificial electric fields generating from a device towed by the survey vessel.

3) Estimation results

In both the LWD method and core analysis method, the volume of methane hydrate lying inside the Umitaka mound structure was estimated to be approximately 600 million cubic meters in methane gas equivalents. In addition, in the marine controlled source electromagnetic method, AIST also roughly estimated the distribution of the sections showing strong electric resistance, in which methane hydrate seems to be present, to obtain approximately some hundred-millions cubic meters in the same order of magnitude.

Based on these results, AIST finally estimated that methane hydrate lies inside the Umitaka mound structure, the amount of which corresponds to approximately 600 million cubic meters in methane gas equivalents.

4) Concerning the handling of the estimation results

The value above shows the amount of the in-place resource (abundance) regarding methane hydrate, but it is difficult to determine the amount of available recoverable reserves as energy resources at the current moment, given that the recovery technologies are not yet fully established.

In addition, in the process of the estimation above, AIST conducted spatial interpolation work based on the limited information on drilled points and, thus, the estimation results may contain uncertainty to some extent in terms of the shapes, continuous distribution, and geological structures of methane hydrate. Accordingly, the estimated amount, i.e., approximately 600 million cubic meters, should be interpreted as having a certain range of variation.

Furthermore, this survey uncovered the fact that each gas chimney structure and characteristics of the distributed methane hydrates are not uniform. Therefore, it is currently difficult to generalize the estimation results concerning the Umitaka mound structure and apply the generalized value to other gas chimney structures.

3. Examination by external experts and key points thereof

Concerning the estimation results of the amount of methane hydrate resources, ANRE established a Committee for Examination of Estimation Results Concerning the Amount of Shallow Methane Hydrate Resources (chaired by Dr. Hiroyuki Arato, professor, Graduate School of International Resource Science, Akita University) of external experts to discuss the results. The committee held meetings on March 16, July 26 and August 31, 2016, all of which were open to the public, discussed the results and compiled them as shown in the following key points.

  • As a result of three-year surveys, rich and important data and analysis results have been successfully obtained.
  • ANRE’s decision concerning choosing the Umitaka mound structure as a target of estimating the amount of methane hydrate resources offshore the Joetsu region, an area for which some information has accumulated through prior research and methane hydrate is estimated to be accumulated to some extent, is appropriate.
  • Approximately 600 million shallow methane hydrate in cubic meters (abundance) is estimated to exist at the Umitaka mound structure, a value to be interpreted with a certain range of variation.

In addition, the committee examined the appropriateness of the survey methods that were conducted for three years. The key points of the examination results are as follows:

  • The survey methods targeting shallow methane hydrate cover a broad range of steps and are comprehensive even for the limited period of time, and the data is rich and highly accurate.
  • The results imply that gas chimney structures may be categorized into several types by morphological characteristic or internal structure. This effort shows the collection of knowledge that could be a barometer for that categorization.
  • Analysis and examination of the samples and data collected by the surveys are not sufficient, and ANRE has more room to continue surveys.

Furthermore, the committee proposed that it is necessary to determine the potential of resource development in parallel with advancing the research and study concerning recovery technologies.

4. Future actions by ANRE

Based on the discussion results of the committee above, ANRE will take actions as follows, aiming to commercialize shallow methane hydrate:

1) Research and study concerning recovery technologies for shallow methane hydrate

ANRE will launch the research and study concerning the technological concepts for recovering shallow methane hydrate. Such technologies are the fields where commercialization has not yet succeeded in any countries. To achieve this goal, ANRE will call for proposals from the public from the viewpoint of broadly utilizing the knowledge of Japanese industries and other entities (scheduled around by the end of September 2016 as for FY2016 call).

2) Research for the clarification of the amount of available shallow methane hydrate

Aiming to collect information that will be necessary for on-site recovery tests in the future along with the development of the research and study of recovery technologies, ANRE will launch research for the clarification of the amount of available shallow methane hydrate in collaboration with AIST.

In addition, concerning the detailed report on the three-year intensive surveys for ascertaining the amount of the resources, AIST will streamline and finalize the results into a report and publicize it around the end of FY2016.

Reference: Estimated amount of shallow methane hydrate resources

Related press releases

On December 25, 2014 (in Japanese)
On January 22, 2016 (in Japanese)

Release date

September 16, 2016

Division in Charge

Petroleum and Natural Gas Division, Natural Resources and Fuel Department, Agency for Natural Resources and Energy

Ministry of Economy, Trade and Industry1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-8901, Japan Tel: +81-(0)3-3501-1511
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