Hydrochemical features of geothermal reservoir geotemperature field in sandstone porosity and enrichment mechanism of geothermal water:a case study of geothermal reservoir of Guantao Formation in the Lubei
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    Abstract:

    Under the effect of tectonic environment, Lubei plain formed different tectonic units, which contain water- rich geothermal resources with different temperature, salinity, and special chemical composition. Among them, the Guantao Formation is of the most abundant geothermal resources. It has been extensively utilized and has the biggest value of economic exploitation. Correctly understanding the geo- temperature field and hydrochemical field as well as mechanism of geothermal water accumulation has become a major issue. The analysis of the cap rock geothermal gradient of geothermal reservoir and reservoir temperature variation characteristics in the Guantao Formation, combined with the geological conditions, shows that geo- temperature field is controlled by tectonic structure and faults, and relatively high temperature zones are distributed mianly at the convergent areas of uplifts and faults, such as along Wucheng- Gaotang- Lingxian County, Ningjin- Qingyun, Zhanhua- Gudao, Gaoqing- Boxing, etc. The geothermal water types of the Guantao Formation in the study area change from SO4·Cl- Na to Cl- Na, with the mineralization content changing form 4.07 g/L to 18.52 g/L and pH ranging from 7.14 to 8.1.In addition, geothermal water contains plenty of trace elements, which are essential to human health.The change of montmorillonite to chlorite is due to poor potassium and poor magnesium of geothermal water. Geothermal water of the Guantao Formation flows generally from southwest to northeast, but flows from outer part to the center of water table depression cone in urban areas. Our analyses suggest that the origin of Guantao Group geothermal water is the atmospheric precipitation. Based on integrated analyses of depth and thickness of basal conglomerate of the Guantao Formation, as well as geothermal well water level and single well yield, this study reveals the paleo- sedimentary facies and depositional environments of the Guantao Formation in the Lubei plain, and two ancient river channels are divided, i.e. Linqing- Wucheng- Dezhou- Lingxian line and Zhanhua- Hekou- Xianhe line. Linqing- Wucheng- Dezhou- Lingxian ancient river channel is controlled by Gaotang uplift in the south and Chengzikou- Ningjin buried fault uplift in the East, forming a large area of alluvial- proluvial fan with coarse grained rock and big thickness. Zhanhua- Hekou- Xianhe ancient river channel is mainly controlled by the Diaokou and Yihezhunang buried uplift in the northwest and the Wudi buried uplift in the south, forming a large area of alluvial- proluvial fan with coarse grained rock and big thickness. In the downstream, the ancient river channel splits into two parts, influenced by Chenzhuang uplift and Qingtuo uplift, and the southern part of it is mainly distributed along the Lijin- Dongying area. Hot water accumulates along the two ancient river channels, with single well yield of usually large than 85m3/h. The closer glutenite aquifer is to the ancient river channel, the deeper it is buried, and the coarser particle is, the better geothermal water abundance condition will be. Otherwise, geothermal water enrichment condition will be worse. In one word, the alluvial- proluvial fan formed by ancient river has the favorable condition for geothermal water enrichment.

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YANG Xunchang, KANG Fengxin, WANG Xuepeng, FU Qingjie, LIU Zhitao.2019. Hydrochemical features of geothermal reservoir geotemperature field in sandstone porosity and enrichment mechanism of geothermal water:a case study of geothermal reservoir of Guantao Formation in the Lubei[J]. Acta Geologica Sinica,93(3):738-750

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History
  • Received:June 23,2018
  • Revised:October 15,2018
  • Adopted:November 03,2018
  • Online: March 04,2019
  • Published: