深大断裂带温泉溢流的周期效应及深部地下水循环机制研究

The deep circulation groundwater flow system is far from a single water flow model under the condition of a potential sink, but is a complex model formed by a variety of mode transformation influenced by the factors such as fracture, water flow state and so on. Under the action of deep faults, the spillage of hot springs shows stronger periodic dynamic characteristics than that of cold groundwater, which implies important information of controlling geothermal water activity by deep faults. The proposal presents novel approach in utilizing spring outflow's time variations to infer deep fault effect, and adopts advanced method in multiple process coupling based on field observations and tests. In this study, a typical study area is selected in the hydrothermal geothermal field controlled by deep fault along the coast of Guangdong Province, and the accurate continuous time series monitoring and numerical simulation experiments are carried out in the field. A comprehensive analysis of the characteristics of the fault zone and the conditions of deep geothermal state implied by the cyclic variations of spring outflows is made. By monitoring the water head changes with temperature, density, pressure gradient and flow path tracing, we analyze the characteristics of he deep groundwater flow system under the control of deep faults. At the same time, the relationship between the distribution of groundwater thermal dynamic field and the nested structure of groundwater flow system is established. The circulation and evolution of deep groundwater are re-examined from the point of view of hydrodynamic mechanism, by putting forward the development model of multi-stage groundwater system under the control of deep fault. The hydrodynamics study of deep faults could reveal characters of deep geothermal systems, and can provide data and potential useful insights to hydrogeology and geothermal resources.

深循环地下水流系统远不是某一势汇条件下的单一水流模式，而是受断裂、水流状态等因素影响，多种模式转换形成的复杂模式。在深大断裂作用下，深部来源温泉溢流表现出比地下冷水更为强烈的周期性动态特征，隐含着深大断裂对地热水活动控制的重要信息。开展深大断裂带地下水流系统水-热耦合模拟研究，其结果更接近实际地下水流模式，可加深对深部地下水循环规律的理解，避免对地下水补径排的错误认识。本项目拟选取广东沿海受深大断裂控制的水热型地热田为典型研究区，开展野外精准连续时间序列监测与数值模拟实验，全面分析深大断裂带温泉溢流周期效应隐含的断裂带特性及深部地热状态条件等信息，从水头、温度、密度、压力梯度等角度，建立地下水热动力场分布与地下水流系统嵌套结构的关系，从水动力机制的角度重新审视深部地下水的循环和演化。本项目研究成果对揭示深大断裂的水动力机制等深部地热系统的新规律，完善地下水流系统理论及其推广具有重要意义。

深循环的地下水流系统远不是某一势汇条件下的单一水流模式，而是受断裂、水流状态等因素影响，多种模式转换形成的复杂模式。开展深大断裂带地下水流系统水-热耦合模拟，其结果更接近实际地下水流模式，可加深对深部地下水循环规律的理解，避免对地下水补径排的错误认识。本项目通过野外精准的连续时间序列观测与分析方法，描述了温泉溢流的周期性特征并结合固体潮的波动规律，揭示了固体潮对深大断裂地下水动态的控制机理；根据断裂带地下水系统自然状态下可能的热量和质量传递方式，建立了同时包含地下水水流和热量运移的三维非等温非稳定流数学模型，通过将地下水流方程和温度场方程耦合起来，并对这一系统形成的深部热状态及浅部地质条件进行了系列数值试验；根据实际盆地地热水固体潮效应理论研究成果，揭示了温泉溢流周期性变化隐含的深大断裂带特征及深部地热的状态条件，并利用模拟计算得到的地下水动力场及温度场分布特征来识别典型深大断裂地下水系统的深循环成因循环模式。通过上述野外精准的连续时间序列监测与数值模拟实验，全面分析了深大断裂带温泉溢流周期效应隐含的断裂带特性及深部地下水状态条件等信息，从水头、温度、密度、压力梯度、水流路径等角度，研究了深大断裂控制下的深部地下水流系统，建立了地下水动力场分布与地下水流系统嵌套结构的关系，提出了深大断裂控制下多级次地下水系统发育模式，从水动力机制的角度重新审视深部地下水的循环和演化。本项目研究成果对于发展与完善地下水流系统理论及其推广应用具有重要意义。