Construction of Evaluation System for Hydrothermal Resources Using Soil Gas Method

土壤气体法热液资源评价体系构建

• 批准号: 08555259
• 负责人: OHMI Michito
• 金额: $ 3.52万
• 依托单位: Kumamoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08555259/
• 关键词: Radon; alpha particle; Soil gas; Scintillation counter; Hot spring; Volcanic activity; Hydrothermal; Fault; シンチレーションカウンター

The system to estimate the condition of hydrothermal fluids in the shallow subsurface has been proposed based on the temporal and spatial variations of radon concentration contained in soil gas. The results obtained are summarized as follows.(1)The observation holes of 1 m depth for the radon measurement were equipped at the three hot spring areas with fumaroles in the western side of the Aso volcano, central Kyushu, southwest Japan. These areas are considered to be located on a north-south striking fault. Using the scintillation counter method, the number of alpha particles attributable to the decay of ^<220> Rn and ^<222> Rn for 20 minutes were counted. These measurement data were processed by the calculation theory for the number of radon at the start of measurement, and the number of ^<222> Rn which has longer half-life than ^<220> Rn and the age of radon gas were obtained. It was found that the temporal variations of those quantities correspond with the activities of volcanic micr … More o-earthquakes in the Aso area.(2)The lineaments around the hot spring areas were automatically extracted using the Segment Tracing Algorithm and the subscene of the SPOT Panchromatic imagery with high spatial resolution. By the combination of these lineaments and the digital elevation model data, the fault which has a role of conduit for the hydrothermal fluids was estimated to be a reverse-fault type and dip 80ﾟ east.(3)A numerical simulation method for the three-dimensional flow analysis of hydrothermal fluids has been constructed using a finite element method. Three rock types, the basement rocks, the Quaternary volcanic roocks, and the fault fracture zone, were assigned to the study area for the simplification of analysis, and the geologic structure was modeled by the distribution of these rock types. Using this model and the simulation method, the changes of temperature and pressure in the shallow subsurface, which may be caused by the change of hydrothermal fluids condition in a deep part, were calculated. This calculation clarified that these physical quantities change sensitively at the site with large convection of hydrothermal fluids, and consequently, the radon concentration varies remarkably. The site at which the temporal changes of radon concentration are related closely to the volcanic earthquakes, therefore, is considered to have high geothermal potential.Based on the above results, an evaluation of hydrothermal resources reguires the three steps : estimation of three-dimensional distribution of continuous fractures through the combination of satellite images and digital elevation model ; detection of a site having distinctive feature in temporal variation of radon concentration ; and execution of numerical simulation for hydrothermal flow, taking the change of radon concentration and the fault distribution into account. Less

基于土壤气体中氡浓度的时空变化，提出了估算浅层地下热液状态的系统。所得结果总结如下：(1)在日本西南部九州中部阿索火山西侧3个有喷气孔的温泉区设置1 m深的氡观测孔。这些地区被认为位于一条南北走向的断层上。利用闪烁计数法，计算了^<220> Rn和^<222> Rn在20分钟内衰变的α粒子数。用测量开始时氡数的计算理论对这些测量数据进行了处理，得到了半衰期长于氡的^< 222>rn的个数和氡气的年龄。研究发现，这些量的时间变化与阿索地区火山微震活动相对应。(2)采用分段跟踪算法和高空间分辨率的SPOT全色图像子场景自动提取温泉区域周围的轮廓。结合这些特征和数字高程模型资料，估计该断层为逆断层类型，倾角为80‰东，对热液流体具有输送作用。(3)采用有限元法建立了热液流体三维流动分析的数值模拟方法。将基岩、第四纪火山岩和断裂破碎带3种岩石类型划分为研究区进行简化分析，并根据这些岩石类型的分布模拟地质构造。利用该模型和模拟方法，计算了深部热液条件变化可能引起的浅层地下温度和压力的变化。计算结果表明，这些物理量在热液对流较大的位置变化敏感，因此氡浓度变化显著。因此，氡浓度的时间变化与火山地震密切相关的地点被认为具有较高的地热潜力。基于上述结果，热液资源评价需要三个步骤：通过卫星图像和数字高程模型相结合估算连续裂缝的三维分布；氡浓度时间变化有显著特征的地点的检测；并进行了考虑氡浓度变化和断层分布的热液流动数值模拟。少

项目成果

Koike K,Kaneko K: "Characterization and Modeling of Fractures' Distribution Using Fractal Theory" Geothermal Science & Technology. vol.7(in press). (1998)

Koike K，Kaneko K：“使用分形理论对裂缝分布进行表征和建模”地热科学

田原和寛,吉永徹,小池克明,大見美智人: "噴気帯と活断層上でのラドン濃度の時間的・空間的変化" 資源・素材学会春季大会講演要旨集. 1巻(印刷中). (1997)

Kazuhiro Tahara、Toru Yoshinaga、Katsuaki Koike、Michito Omi：“喷气孔带和活动断层上氡浓度的时间和空间变化”日本自然资源和材料学会春季会议摘要第 1 卷（正在出版）。 1997）

冨田諭, 吉永徹, 小池克明: "噴気帯におけるガスと湧水中のラドン濃度の解析" 資源・素材学会1998年春季大会講演要旨集. 印刷中 (1998)

Satoshi Tomita、Toru Yoshinaga、Katsuaki Koike：“喷气孔区气体和泉水中的氡浓度分析”日本资源材料学会 1998 年春季会议摘要已出版（1998 年）。

小池克明,葦彬: "Azimuthal Distribution Analysis of Faults Using Satellite Images" Proc.of Forth Int.Symp.on Mineral Exploration, 96. 1巻. 82-84 (1996)

Katsuaki Koike、Akira Ashi：“利用卫星图像进行断层方位分布分析”Proc.of Forth Int.Symp.on Mineral Exploration，96. Volume 1. 82-84 (1996)

小池 克明: "噴気帯と活断層帯におけるラドン濃度の時間的・空間的変動の特徴" 佐々宏一教授記念論文集. 221-230 (1997)

Katsuaki Koike：“喷气孔带和活动断层带氡气浓度的时空变化特征”Koichi Sasa 教授纪念论文集 221-230 (1997)。