综合物探方法勘查福建贵安地热田

APPLICATION OF GEOPHYSICAL METHODS TO GUIAN GEOTHERMAL FIELD EXPLORATION

福建东南沿海地热田主要受断裂控制，温泉多为中低温水热系统，适用于直接供热。在该区典型地热田之一的贵安地热田进行了４种物探方法试验研究：大地电流和声频大地电磁测深、自然电场法、地面磁测、一米测温。由于温度并非是影响电阻率变化的唯一因素，因此仅仅根据电阻率值并不能区别高温带与低温带。研究表明：大地电流和声频大地电磁测深资料的定性和定量解释所获取的电阻率分布可确定断裂构造在地表以及向地下延伸分布特征；另外３种方法在某种程度上反映构造或温度变化，可以有效地圈定热田中心部位。例如，构造破碎带可以引起负磁异常；自然电位正异常与上涌泉相关；浅孔测温高值带与热田最高温泉相对应等。

The hot springs in southeastern coast of Fujian Province, mainly controlled by fault/fracture zones, are low to moderate temperature hydrothermal resources for direct utilization. The arms of comprehensively geophysical methods applied to Guian hydrothermal system, one typical geothermal field in the area, are to detect the system center precisely and to site drills economically. Four methods have been used in this field: (a) telluric and audio frequency magnetotelluric sounding (T AMT); (b) self potential (SP); (c) ground magnetometry; d) temperature logging in one meter holes. The surface and subsurface fault/fracture zones, as water channel in the field, can be determined by the resistivity distribution obtained from the qualitative and quantitative interpretation of T AMT data. But it is difficult to distinguish the high temperature zones and lower ones only in terms of the resistivity values since the temperature is not the only factor contributing to the resistivity variation. The other three methods, to some extent, reflecting the temperature variation or substructure character are effective in determining the hydrothermal center. The negative anomaly of vertical component of magnetic field is considered as the fault zone; the positive SP anomaly results from the ascension springs and the high values of temperature logs in one meter holes are consistent with the hottest spring (89℃) in this field.