Establishment of Evaluation Techniques for the Behavior of Rock Tanks in Natural Gas Hydrate Storage at Low Temperatures

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K05350
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31020:Earth resource engineering, Energy sciences-related
• Research Institution: Ehime University
• Principal Investigator: Kinoshita Naoki 愛媛大学, 理工学研究科(工学系), 准教授 (30263958)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 氷飽和度 / ガス浸透性 / 弾性波速度 / 凍結ベレア砂岩 / 岩盤タンク / 天然ガスハイドレート

Outline of Final Research Achievements

In this study, gas permeability experiments were conducted on Berea sandstone at low temperatures, which have not been done before, to evaluate the effect of ice saturation on the permeability. As a result, it was confirmed that the permeability tended to decrease with an increase pore fluid pressure. Compared to the initial permeability measured at 20°C, the permeability measured at -20°C showed a smaller value. Furthermore, it was observed that the permeability decreased with increasing ice saturation. The water permeability was estimated by taking into account the Klinkenberg effect, and the change in permeability was examined using the Kozeny-Carman equation. As a result, the permeability at a pore occupation ratio of 0, estimated from the regression curve, tends to overestimate the permeability obtained from the water permeability experiments.

Free Research Field

岩盤工学

Academic Significance and Societal Importance of the Research Achievements

岩盤タンク方式では地下水により石油および石油ガスを封じ込め，気密性を保つ水封式が取られ，そのシステムは確立されている。この方式は，必要な土地面積が少ない，地震，落雷など自然災害に強い，漏出，拡散の危険性が低い，景観への影響が少ないなどのメリットを持っている。ただし，NGHを地下岩盤タンク内に備蓄する新たな技術の確立のためには，低温下における岩盤の気・液浸透特性，力学・変形特性を精密に定量評価，把握することが必要であり，岩盤タンクの挙動，堅牢性，気密性の評価技術が不可欠となる。本研究成果はこれらの基礎的資料となるものであり，本研究により社会実装に向けて技術が向上したと考えられる。