distribution mapping of rock stress in the northern area of japan estimated by the core deformation method and drilled cores and its application to geothermal development

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04958
• 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: Tohoku University
• Principal Investigator: Ito Takatoshi 東北大学, 流体科学研究所, 教授 (00184664)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 地殻応力

Outline of Final Research Achievements

We sampled a number of rock cores obtained from geothermal wells, and measured their cross-sectional shapes and Young's modulus E. It was found that the diametrical difference in core diameter and E varied in a wide range with the depth at which the core was drilled. However, those two values were inversely proportional so that the stress difference estimated by the core deformation method was to be nearly constant. The result indicates that the core deformation method can be applied to the cores obtained by a general way of drilling in order for stress estimation. Furthermore, it was found that absolute magnitudes of horizontal stresses can be estimated from the stress differences estimated on the cores obtained from vertical and inclined boreholes.

Free Research Field

エネルギー資源開発に関わる地下岩体の力学挙動の評価ならびに大深度を対象にした地殻応力測定法の開発

Academic Significance and Societal Importance of the Research Achievements

地殻応力は、地震・火山現象のみならず、例えば地熱流体の流動に大きく影響する。しかし、従来の地殻応力測定法は高価なため、ピンポイントにデータが限られていた。一方、様々な目的で過去に掘削された坑井が各地に多数存在する。そこで得られたコアと本研究で明らかにした地殻応力評価法を組み合わせれば、従来得られなかった地殻応力の面的な分布が明らかとなり、地震・火山現象や地熱流体の流動の理解が大きく前進すると期待される。