イランにおける地熱開発の関心は, 1974年国連の地熱専門家J.R.McNitが同国を訪問したことから始まった。1975年に, イタリアのENELとイランのTBとの間で, イラン北西部の地熱開発についての契約が結ばれた。その結果, 1983年には, 有望地域として, サバラン, ダマバンド, コイ・マクおよびサハンドの4地域が抽出された。1996年から1999年にかけて, 国家規模の地熱資源量調査がエネルギー省のイラン再生可能エネルギー機構によって行われ, さらに10カ所の有望地域が抽出された。以上の14地域のうちで, サバラン地域が精密調査のための最初の地熱地域に選ばれた。1996年以降, 調査掘削および地熱貯留層評価のためのフィージビィリティスタディがニュージーランドのKMLによって行われた。2001年から2004年にかけて, 地下地質構造の把握, 地熱貯留層評価および生産に伴う貯留層状態変化の予測シミュレーションのため, 3本の深い坑井が掘削された。それらのうち, 2本は成功し, 最高温度240℃ (3200m深) が記録された。地熱貯留層シミュレーションの結果, 55MWの規模の地熱発電所が, イラン最初の地熱発電所として, サバラン地域に計画された。必要な蒸気量を生産するために, さらに13本の生産井と還元井が計画されている。現在, 坑井掘削基地の建設が行われている。2007年遅くには掘削が開始される予定である。

抄録全体を表示

Geothermal activity has been considered to have close relation with volcanic activity, but this relation is not examined so much.This paper examined the relation by reviewing the following two aspects. The first aspect is on the difference of geothermal activity. Some volcanoes have intense geothermal activity, while other volcanoes have no geothermal activity. This difference was found to depend on the stress field around volcanoes.In tensile stress field, magma can easily create its path to ascent and secure certain space to store. The second aspect is on the variety of precursor of eruptions including failed eruptions. For instance, Sakurajima Volcano frequently has eruptions after seismic swarm and/or ground deformation. In Asama Volcano, similar phenomena have been observed until eruptions in 1973. On the other hand, eruption has not occurred in Iwate Volcano, though many precursory phenomena such as deformation of volcanic body and increase of seismic activity indicating magma intrusion were detected.Expansion of geothermal activity was detected just on the hypocenter zone. In recent activity of Asama Volcano, the correspondence of the seismic swarm and the eruption has changed to be unclear and the prediction of the eruption turned to be difficult. Increase of geothermal activity is frequently observed after magma intrusion associated with seismic swarm, but no magmatic eruption occurs in many cases and phreatic eruptions occur in some time. These differences originate in the variety of easiness of magma ascent.
From the above review, this paper proposes the following idea; volcanic activity has two end members depending on the easiness of magma ascent.The type of volcanic activity will be ‘Eruption dominant’ (ED) when the magma easily ascends to the ground surface, while it will be ‘Geothermal activity dominant’ (GD) in the opposite case.Various kinds of volcanic activities are defined between these end members. The easiness of magma ascent depends on some certain conditions.This paper indicates three possible factors; regional stress, density difference between magma and medium, and degassing from magma. Research on geothermal activity and volcanism is requested to examine these factors, because this idea may present us more systematic understanding of volcanism.

抄録全体を表示

The research and development on geological disposal of high-level radioactive waste from the atomic power generation has been carried out in the Horonobe field, the north-western Hokkaido.In the Horonobe field, investigations of 8 boreholes were carried out as the Horonobe Underground Research Laboratory Project by 2004. These investigations clarify the diagenetic mineralogy and water chemistry, and show that the geology comprises the diatomaceous sediments containing pyrite, calcite and siderite as authigenic accessory minerals, and that the groundwater is a mixture between meteoric water in shallow depth and saline water in deep underground.
Relative abundance of pyrite and carbonate is estimated by X-ray diffraction analyses, mode analyses of thin section, and whole rock compositions of SO42, TIC (Total Inorganic Carbon) and (Fe24-/total Fe).Based on the mineralogical analyses, the mineral fronts where relative abundance of the minerals abruptly changes are confirmed.Comparing the mineral fronts with the corresponding water chemistry, the mineral fronts of 2 boreholes in the western part of the field are situated in the saline water zone, but these of other boreholes are situated in the meteoric water zone. Assuming that pyrite and carbonate are stable in the saline water zone because these minerals abundantly occur in the saline water zone, the mineral front in the meteoric water zone is supposed to be remained in spite of water/rock interaction. The occurrence of the mineral fronts in the respected water zones would be attributed to kinetic interaction, suggesting that saline water is discharged upward in the western part of the field, and that meteoric water is recharged downward in other area.

抄録全体を表示

We have developed a numerical model of Geothermal Heat Pump (Geo HP) Systems as an element in the simulator of Integrated Renewable Energy Systems (TRES). The numerical model of Geo HP systems consists of three parts;one is heat extraction fluid in U-tube, the other is layer around the U-tube, and the other is heat pump. The model, which represents temperature variation of heat extraction fluid, is based on the one-dimensional advection-diffusion equation and the heat flow equation between the fluid and the layer. The model, which represents temperature variation of layer, is based on the equation of heat conduction in the cylindrical coordinate system.The model, which represents power variation of heat pump, is based on the capacity diagram released from the heat pump manufacturer. We have confirmed the feasibility of developed model of Geo HP systems by comparing the data calculated from the model of Geo HP systems with the real data of temperature of heat extraction fluid during the thermal response test under the condition of constant heating. It has been revealed that the calculated temperature using the model well agrees with the measured temperature profile, even though there are some inconsistencies around the beginning and after the end of heating due to the simplified model. Therefore, we have reached the conclusion that the developed model of Geo HP systems can represent the dynamic behavior of GeoHP systems enough to use for the IRES simulator.

抄録全体を表示