川东褶皱带地热系统的空间载体——相互连通的断裂系统：以四川广安牟家镇地热井为例

Spatial carrier of geothermal system in eastern Sichuan fold zone——interconnected fault system： A case study of geothermal well in Moujia Town, Guang'an, Sichuan

关键词:  川东褶皱带  相互连通的断裂系统  地热系统  产研结合

Key words:  eastern Sichuan fold belt  interconnected fracture system  geothermal system  combination of production and research

摘要:

在“双碳目标”背景下，发展低碳能源势在必行。作为重要的清洁能源，地热资源勘查及开发利用力度亟须加大。在地热资源丰富的川东褶皱带，已有研究认为，该区三叠系嘉陵江组灰岩地层是有利的热储层，也是地热勘查的主要目标体。然而，众多钻遇嘉陵江组未出地热水及未钻遇嘉陵江组出现地热水的事实，对此提出了质疑。本文在牟家镇地热勘查区，通过音频大地电磁测深发现勘查区深部存在相互连通的断裂系统，并以此为目标体进行钻孔验证，获得了日涌水量>12000m³、42℃的地热水，据此，推测相互连通的断裂系统可能是川东褶皱带地热系统的空间载体。通过探测华蓥山及铜锣山2处天然温泉及1处无水钻孔的深部构造特征，印证了川东褶皱带断裂控水的普适性；结合渗流分析，认为以相互连通的断裂系统为勘查目标体，有望实现川东褶皱带地热资源的可持续开发。本次研究将为带内普适的地热成因机制、勘查实践及可持续开发利用研究提供些许借鉴。

Abstract:

Under the background of "Carbon peak and Carbon neutral", it is imperative to develop low carbon energy. As an important clean energy source, the exploration and utilization of geothermal resources need to be intensified. In the eastern Sichuan fold belt, which is rich in geothermal resources, the limestone stratum of Triassic Jialingjiang Formation is considered as a favorable thermal reservoir and the main target of geothermal exploration. However, the fact that many drilling in Jialingjiang Formation did not produce geothermal water and the geothermal water from other Formation calls into question the above statement. In this paper, in the geothermal exploration area of Mujia Town, it is found that there are interconnected fault systems in the deep part of the exploration area through the audio-frequency magnetotelluric sounding. Using this as the target body for drilling verification, geothermal water with daily water inflow >12000m³ and 42°C was obtained. Based on this, it is speculated that the interconnected fault system may be the spatial carrier of the geothermal system in the eastern Sichuan fold belt. By detecting the deep structural features of two natural hot springs in Huayingshan and Tongluoshan and one waterless borehole, the universality of water control by faults in the eastern Sichuan fold belt is confirmed. Combined with the seepage analysis, it is considered that taking the interconnected fault system as the exploration target body is expected to realize the sustainable development of geothermal resources in the eastern Sichuan fold belt. This study will provide some reference for the research on the ubiquitous geothermal genetic mechanism, exploration practice and sustainable development and utilization in the belt.