Study on the spatial characteristics and genetic mechanism of geothermal resources in Zhangye Basin by multi-source fusion modeling and heat-flow coupling simulation
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摘要: 摘要:传统基于已有钻孔数据插值的温压场分析方法不能很好地反映地热资源渗流-传热耦合过程,造成对地热资源的成因机制认识不足。本文首先基于钻孔信息、物探信息、高程数据等多源数据进行相互融合,建立了张掖盆地高精确度三维地质模型。对比传统插值模型可知,多源数据融合建模能提升孔间地层精度50-300m。基于三维地质模型开展了盆地渗流-传热场耦合数值模拟,对比关键点空间插值法,多场耦合分析更合理地揭示研究区储层温压特征。研究区地热水整体由南东向北西渗流,经断层补给储层,渗流过程中被地温场充分地加热,温度场表现为中间高四周低,中心温度可达78℃;水头在盆地中心靠东南处较高,逐渐向盆地北东方向降低。最后,建立了三维地热概念模型,结合构造、水文地质和地热地质条件等综合解释了盆地地热资源的成因机制。较之以往的二维模型,本文三维概念模型和热-流耦合的方法更准确的描述了资源地空间分布特征和更合理地解释了资源成因机制。Abstract: Abstract: The traditional temperature and pressure field analysis approach, which is based on the interpolation of existing borehole data, cannot accurately represent the seepage-heat transfer coupling process of geothermal resources, resulting in insufficient understanding of the genetic mechanism of geothermal resources. First, a high-precision three-dimensional geological model of Zhangye Basin is built by combining multi-source data including borehole information, geophysical information and elevation data. Compared with the traditional interpolation model, multi-source data fusion modeling can improve the accuracy of inter-hole strata by 50-300 m. The numerical simulation of basin seepage-heat transfer field coupling process is carried out. The results show that the multi-field coupling analysis more reasonable represents the temperature and pressure characteristics of the reservoir than the key point spatial interpolation approach. The geothermal water in the study area flows from southeast to northwest and supplies the reservoir via faults. The geothermal field totally heats it during the seepage process. The temperature field is high in the basin center and low around it, with the central temperature reaching 78℃. The water head is greater towards the southeast of the basin's center and progressively drops to the northeast. Finally, a 3D geothermal conceptual model is developed to explain the genetic mechanism of geothermal resources in terms of structural, hydrogeological, and geothermal geological perspectives. This 3D conceptual mode coupling with heat-flow transfer modeling more specifically explain the spatial distribution and reveal more clearly the underlying mechanism of forming the geothermal resources compared with conventional 2D model.
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