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    关中盆地地温场划分及其地质影响因素

    Geothermal field division and its geological influencing factors in Guanzhong basin

    • 摘要: 具有无污染、可再生、分布广、储量大以及可就近利用等诸多优势的地热能是一种洁净能源,应用前景广阔。地热能的开发利用与区域地温场划分紧密相关,关于关中盆地整体地温场划分的研究鲜有报道。根据关中盆地的工程地质、水文地质、环境地质条件等因素,总结了岩体类和砂土类的热物性质特征。通过灰色关联分析方法,分析了岩土体热物性参数的影响因素,认为干燥重度对导热系数的影响程度最大,含水率、天然重度、孔隙率三者影响程度相近;干燥重度对比热容影响程度最大,天然重度次之,含水率和孔隙率影响最弱。利用盆地内多个地温常观孔,绘制了地温变化曲线和地温梯度等值线,认为关中盆地常温带位于15~20 m埋深处,地温梯度总体呈中部高、东西低,固市凹陷、西安凹陷、蒲城凸起、断裂及断裂汇合区域地温梯度较大,宝鸡凸起、咸礼凸起以及临蓝凸起地温梯度较小,产生差异的原因包括地质构造、地下水活动、岩土体热物性参数等三方面。利用热物性参数和地温梯度值,计算了盆地内浅层和深层的大地热流值,并分析了两者差异的成因,经对比全国区域地热资料,认为关中盆地是一个复杂的坳陷型中低温地热田,地热资源潜力巨大,居全国上游。该文旨在系统地分析关中盆地地温场特征,为地热能的勘查评价提供基础数据支持,促进关中盆地地热开发利用,为构建环境友好型社会服务。

       

      Abstract: Shallow geothermal energy is a renewable and widely distributed clean energy, it has broad prospects for development and utilization. The exploitation and utilization of geothermal energy are closely related to the division of regional geothermal field; nevertheless, there are few reports about Guanzhong basin at present. Based on regional geological and hydrogeological conditions and the classification of lithology, the authors summarized the thermal properties of rocks and soil. The influence of soil thermal conductivity and the specific heat capacity based on gray relational analysis reveal the main factors controlling the thermal conductivity and specific heat. The drying severity has the greatest impact on the thermal conductivity, whereas water content, natural gravity and porosity exhibit similar influences. The dry severity has the greatest impact on the specific heat capacity, followed by the natural gravity, whereas the water content and porosity play the weakest role. Based on the long-term observation data of downhole temperatures in the Guanzhong basin, the authors presented downhole temperature logs and temperature gradient contours. Normal temperature zone lies in the depths of 15-20 m in Guanzhong basin. The geothermal gradient is high in the middle part and low in the east and west part. The areas with large geothermal gradient include Gushi depression, Xi'an depression, Pucheng bulge and faults. The geothermal gradient of Baoji bulge, Xianyang-Liquan bulge, and Lintong-Lantian bulge is relatively small. The reasons of the differences include geological structure, groundwater activity and thermal and physical parameters of rock and soil. The heat flow in the basin was calculated using thermal physical parameters and geothermal gradient values, and the reasons which produce the heat flow difference between the shallow and the deep were analyzed. Compared with the regional geothermal background, the Guanzhong basin is hotter and its geothermal resources are abundant. The purpose of this paper is to systematically analyze the characteristics of the geothermal field in the Guanzhong basin so as to provide a basis for exploration and evaluation as well as the development of geothermal energy and to serve the construction of a good environment and society.

       

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