基于钻孔测温的地球化学温度计适宜性评价：以雄安新区为例

The geochemical geothermometer is a common method for estimating the temperature of deep thermal reservoirs, which is widely used where no boreholes are drilled or the borehole depths do not reach the geothermal reservoir.However, the calculation results of the geochemical geothermometer were generally compared to the wellhead temperature in the previous studies.Comparison studies with the measured temperature of the borehole are few, which results in uncertainty of the geothermometers.In this study, 12 geothermal wells in the geothermal field with detailed research basis and abundant data in Xiong'an New Area, Jizhong depression, North China Plain, were selected to evaluate the reliability of the geothermometer in conjunction with water temperature measurement, borehole logging, and geothermal water collection and analysis.Nineteen geochemical geothermometers were used to estimate the thermal storage temperature of geothermal water after the evolution of water-rock interaction and multimineral thermodynamic equilibrium simulation.And then the results were compared with the measured borehole temperature and wellhead temperature.Results show that when the wellhead temperature in the study area is less than 70 ℃ , the wellhead temperature falls within the range of the actual borehole temperature from the thermal reservoir roof to the floor.However, when the wellhead temperature exceeds 100 ℃ , the wellhead temperature is lower than the thermal reservoir roof temperature and much lower to the bottom plate temperature.They are affected by several factors such as cooling, decompression, phase separation, CO 2 degassing, and SiO 2 precipitation during the transport process, which should be paid great attention in the future.Secondly, the geothermal water in Jixian karst-fissured reservoir belongs to immature water, and the cation geothermometer is not applicable, while the geothermal water in the porous Neogene sandstone reservoir is mainly located in a partial equilibrium area which implies the feasibility of both cation and SiO 2 geothermometer.The borehole temperatures were used to verify the suitable geothermometers.It is found that the chalcedony solubility geothermometer is suitable for Jixian karst-fissured reservoir with a deviation of 6.2 ℃ , while the Na-K geothermometer and chalcedony geothermometer are suitable for the porous Neogene sandstone reservoir with a deviation of 6.0 ℃ and 3.4 ℃ , respectively.Finally, a variety of geothermometers are recommended to be selected with constraints of stratigraphic information, rock characteristics, wellhead temperature, and so on.And if the borehole logging is not available, underground temperature can be roughly understood with geochemical geothermometers at different sampling depths under the same geological structural unit.Our results have significant implications for the application of geochemical geothermometers and sustainable management of geothermal resources.