Abstract:
This paper is the result of geothermal geological survey engineering.
Objective Burial depth and temperature are important parameters for evaluating the resource potential of hot dry rocks (HDRs). the Distribution characteristics of granite bodies in typical geothermal fields in Hunan and assessing their resource potential is of great significance for the site selection of regional HDR exploration targets and the determination of exploration depth.
Methods Based on the pipeline model, the buried depth characteristics of the HDR in Huitang and Reshuixu geothermal fields in Hunan Province are discussed. By establishing three-dimensional geological models of the two typical granite bodies, i.e., Weishan and Dongling, and combined with the basic parameters in Hunan Province, such as terrestrial heat value, rock thermal conductivity, rock heat generation rate and other basic parameters in Hunan Province, the temperature field characteristics of the two typical HDR resource potential areas are calculated and analyzed. The resource potential of these two typical granites is evaluated by model method and volume method respectively.
Results Based on the pipeline model, the buried depth of the HDRs in the Huitang and Reshuixu geothermal fields is 3.63~4.65 km and 4.08~4.31 km, respectively. While the geothermal gradient of the two geothermal fields is 3.51~4.54℃/100 m and 3.79~4.0℃/100 m, respectively, much higher than that of the other areas in Hunan Province. The highest temperature at 5 km depth of the Weishan granite can reach 212.2℃, and the highest temperature at 5 km depth of the Dongling granite can reach 210.8℃. The 3~10 km resource of Weishan granite body calculated by the model method is 4715.5×1018 J, and by the volume method is 5016.1×1018 J. The 3~5 km resource of Dongling granite body calculated by the model method is 265.8×1018 J, and by the volume method is 282.6×1018 J.
Conclusions The Moho surface and Curie surfaces of Huitang and Reshuixu geothermal fields are shallower than the adjacent areas. The high heat flow area is formed by the combination of many factors, such as the residual heat of magma and the high heat generation rate of rocks caused by special crustal structure and intense regional tectonic activities. Compared with the other areas of Hunan Province, Weishan and Dongling granites are rich in HDR resources, with shallow burial and high temperature. The results of assessment can provide reference for the location selection of HDR targets area and the determination of the appropriate depth for HDR resource exploration in Hunan Province.
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