地热驱动力:广东阳江新洲地热田驱动地热水运移的一种额外非重力作用的分析方法

Geothermal driving force: A new additional non-gravity action driving the migration of geothermal water in the Xinzhou geothermal field of Yangjiang, Guangdong

Tóth总结提出的"嵌套式多级次水流系统",和张人权等学者归纳总结的重力驱动地下水流系统理论,是地下水运移的重要理论基础。地下水的流动可能受到重力势、压实势、构造挤压力共同作用。然而,在对流型水热系统中发现了地下水补给区位置低于排泄区的反常现象。由于温度升高导致地热水密度减小和压力增大,使得地热水的实际压力水头增大,是出现这种反常现象的物理基础。笔者定义这种额外增大的压力水头为"地热驱动力",分析其大小与地热水温度、盐度、黏滞度的关系并给出量化计算方法。在广东阳江新洲地热田的研究实例中,地热驱动力的启动点位于地热水循环的最深处4.34 km,该处由温度升高产生的地热驱动力的标准水头为+351.59 m,由盐度增加产生的地热驱动力的标准水头为-2.78 m,总的地热驱动力的标准水头为+348.81 m。地热水温度越高,地热驱动力越大;盐度越大,地热驱动力越小。地热驱动力的额外加持作用可以加快水热系统中地下水的循环。

The "nested multilevel flow system" summarized by Tóth and the gravity driven groundwater flow system theory summarized by Zhang Renquan et al are the important theoretical basis for groundwater migration.Groundwater flow may be affected by gravitational potential, compaction potential and tectonic compression force.However, the anomalous phenomenon that the groundwater recharge area is lower than the groundwater drainage area is found in the convective hydrothermal system.As the temperature rises, the density of geothermal water decreases and the pressure increases, and the actual pressure head of geothermal water increases, which is the physical basis for this abnormal phenomenon.This paper defines the additional pressure head as "geothermal driving force",which is related to the temperature, salinity and viscosity of geothermal water.And we propose a quantitative calculation method.In the case of Xinzhou geothermal field in Yangjiang, Guangdong Province, the starting point of the geothermal driving force is located at the deepest part of the geothermal water cycle of 4.34 km, where the standard head of the geothermal driving force generated by temperature rise is +351.59 m, and the standard head of the geothermal driving force generated by salinity increase is-2.78 m, and the standard head of total geothermal driving force is +348.81 m.The higher the geothermal water temperature is, the greater the geothermal driving force is.The greater the salinity, the smaller the geothermal driving force.The additional supporting effect of geothermal driving force can accelerate the circulation of groundwater in hydrothermal system.