雄安新区容城地热田深部热流体循环与演变机制

Rongcheng geothermal field plays an important role in the Xiongan New Area geothermal research, but the distribution and genetic mechanism of its thermal reservoir in the deep bed rocks still remain unclear. This project aims to use the deep carbonatite geothermal reservoir in the geothermal field as the investigated object. Based on the collection of the latest deep geophysical exploration, deep geothermal drilling results and regional geological structure data, combined with systematic geothermal fluid and rock sampling, geochemical characteristics of geothermal fluids and geothermal field characteristics, comprehensive deep geothermal analyses in the study area were obtained. In addition, the sources of the fluid materials was constrained, whereas the geothermal reservoir temperature of deep carbonatite was estimated; The results of geochemical and isotopic data of the rocks were used to characterize the deep hydrogeochemical processes, and to reveal the genetic mechanism of the deep carbonatite thermal reservoirs. This project will enrich our understanding of the medium-low temperature geothermal system, and offer a scientific reference for the development and utilization of the deep geothermal field in the Xiongan New Area.

作为雄安新区地热资源重要组成部分的容城地热田，深部基岩热储的分布及成因机理尚不清楚。本项目拟选取该地热田深部碳酸盐岩热储为研究对象。在收集最新的深部地球物理探测及深部地热钻探成果和区域地质构造资料的基础上，进行系统地地热流体、岩石样品采集工作，研究地热流体地球化学特征，分析地温场特征，识别研究区深部地热流体物质来源及成因，估算深部碳酸盐岩热储层温度；分析岩石地球化学及同位素数据，刻画深部水文地球化学过程，揭示深部碳酸盐岩热储成因机制。该项研究成果将不仅丰富中低温地热成因系统，同时对区内深部地热开发利用工作提供科学的参考依据。

作为雄安新区地热资源重要组成部分的容城地热田，地下热水所处热储主要为蓟县系碳酸盐岩热储，为揭示深部碳酸盐岩热储的成因机制，项目在收集最新的深部地球物理探测、深部地热钻探成果和区域地质构造资料的基础上，进行了地热流体地球化学分析、地温场特征分析、热储层温度估算等工作。研究结果显示：研究区地热水的水化学类型以Cl·HCO3-Na型为主，TDS与Na+和Cl-成正相关，说明发生淋滤和阳离子交换作用，水-岩相互作用强烈；通过地热水同位素分析，地热流体来源于大气降水；反向地球化学模拟在一定程度上证明了地热流体在长距离运移过程中伴随有矿物的沉淀和溶解现象；利用流体化学地温计估算热储平均温度70℃。研究提出的容城地热田成因模式认为：雄安新区蓟县系雾迷山组热储中地热流体来源于西部太行山隆起的基岩出露区，通过区域性深大断裂运移至地热田所处的冀中坳陷地区，并由导水断裂、裂缝向“坳中凸”的容城凸起汇集，在此长距离径流过程中与碳酸盐岩发生水岩相互作用并吸收由壳源幔源提供的热量，形成地下热水。