典型深大断裂地热田温泉周期动态及固体潮效应表征的数值实验研究

Deep faults are the key passages of deep geothermal heat flows. However, it is difficult to understand because of being deep down inside the crust, and thus limiting our knowledge about geothermal energy and its development and utilization. We adopt novel approach in utilizing cyclic variations of thermal springs to characterize functions of deep faults in geothermal fields. The proposal is focused on the scientific problem that how deep the deep fault in geothermal field cuts into the crust, and how this would affect the heat conduction, and the geothermal flow system. The working hypothesis is that the deep fault in geothermal fields could cut into the crust, deep enough to even reach high-temperature supercritical water zone; and that the geothermal fluids within the deep fault can be affected significantly and change cyclically under solid tidal waves. The study utilizes advanced method in combining geothermal flow time-serial data, hydrogeological tests and aqueous chemistry data, and employing state-of-art numerical experiments in thermal, hydrological, and mechanical (THM) process couplings. 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.Research results are anticipated to reveal the hydrodynamics within deep fault in deep geothermal system, and to provide new theoretical findings regarding the heat source for large scale geothermal fields. 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, and elevate the status of relevant research areas in our country.

深大断裂是地热田深部热流的关键通道；但其主体位于地壳深处，难以研究了解，制约了地热资源的认识和开发利用。本项目通过典型温泉的周期动态、区域水文地质环境调查，研究深大断裂系统及地热田的特性，进一步探讨科学问题：地热田深大断裂的切入程度如何影响地热及地热水系统。目标是验证深大断裂的固体潮效应假说: 地热田深大断裂切入地壳内部，甚至深及高温超临界水地带；温泉溢流周期性变化，隐含着断裂带特征及深部地热的状态条件等信息。研究方法是在整合野外水文环境地质、动态数据信息基础上，运用国际上尖端的热力、水流、力学THM多过程耦合数值实验。从温泉动态推断深大断裂效应，手段新颖；采用野外研究与尖端的数值实验结合，方法先进；研究成果预期可揭示深大断裂的水动力机制等深部地热系统的新规律，对大规模地热田的深部热源提供新的理论认识。项目可为水文地质、地热资源等学科提供一批科学数据与潜在成果，提升我国相关研究的国际地位。

深大断裂切入地壳深层部位，深处扎入高温高压环境条件部位，浅处出露地表； 深大断裂在有利部位往往成为地热流体(深部地下水)的优势通道。项目的前期工作显示典型深大断裂温泉流量具有显著的周期性变动，随月亮的圆缺而有初一十五的大变幅周期，每天的地球自转的两起两落。..主要研究内容有： 1.深大断裂的区域水文地质与水文地球化学环境条件； 2.典型深大断裂地热田的温泉动态的周期性；3.深大断裂地下水流场特征刻画；4.深大断裂水文地质性质刻画。..重要结果包括 深大断裂地热水的pH值随温度升高而普遍地下降，在高温区域(200-300oC)地热水处于酸性，而且还原状态。 深大断裂伴随的优先流动通道导水能力强，渗透性可比砾石粗砂；地热田地热水体系形成穹隆状测压水头面。 深大断裂的深部流场的影响半径能够达到十到二十公里。 深大断裂温泉在固体潮周期性变化作用下，水流发生变动，叠加出现低压异常。该低压现象与地震活动有关联，待进一步深入研究其成因。..关键数据及其科学意义在于 本项目获取的数据涉及深部流体的状态及深大断裂的导水性质。有关科学的涵意表现在基础理论认识，涉及深部地热开发、地下水循环深度、深部流体压力传播等。