谷露地热田热结构初探及高温异常区预测  

Preliminary study on thermal structure and prediction of high temperature anomaly area in Gulu geothermal field

作　　者：王闻文 巴桑元旦 吴儒杰[1] WANG Wenwen;BASANG Yuandan;WU Rujie(Beijing Research Institute of Uranium Geology,Beijing 100029,China;Center of Land Mining Rights Trading and Resource Reserves Evaluation,Xizang Autonomous Region,Lhasa 850011,China)

机构地区：[1]核工业北京地质研究院,北京100029 [2]西藏自治区土地矿权交易和资源储量评审中心,西藏拉萨850011

出　　处：《世界核地质科学》2024年第1期105-116,共12页World Nuclear Geoscience

摘　　要：谷露地热田是西藏那曲—尼木地热带上典型的高温地热田。对其地下热结构展开深入研究,并建立准确的温度结构模型,具有重要的实用和科学价值。基于经典电阻率和温度转换经验公式,以钻孔处实测温度值和电阻率值作为估算标准,以电阻率比值和深度分层约束为指导思想,建立了适用于谷露地热田的电阻率与温度转换经验公式,并确定了相关经验系数。通过评估音频大地电磁测深剖面电阻率反演结果的有效性,以及钻孔处温度实测值和估算值之间的拟合优度,评价了此次温度估算方法的合理性,并进行了反演电阻率到温度的转换计算。计算结果成功构建了两条音频大地电磁测深剖面所示区域内的地下温度结构模型,并基于此进行了成矿预测。结果表明:Ⅲ号高温异常区与已知钻探成果相符。因此,推断在两条剖面上存在4个浅部高温异常区(Ⅰ、Ⅱ、Ⅳ和Ⅴ)和3个深部高温异常区(Ⅵ、Ⅶ和Ⅸ);其中Ⅶ号异常与F4-2断裂的空间分布密切相关,并存在由深部向上运移的趋势,推断该处温度异常存在较大可能为深部热储的反映。而Ⅵ和Ⅸ号异常则与F4-1断裂密切相关,为下一步勘探提供了新目标。需要注意的是,本次计算基于主要岩性为花岗岩而得出相关经验系数,在不同勘探区域使用时需根据实际岩性和钻孔测温结果重新确定转换公式中所需参数。The Gulu geothermal field which located in the Naqu-Nimu geothermal belt of Tibet,is a representative high-temperature geothermal field.Comprehensive study on its subsurface thermal structure and establishing an accurate model of temperature distribution holds significant practical and scientific value.In this study,we proposed an empirical formula for converting resistivity to temperature specifically tailored for the Gulu geothermal field by utilizing classical resistivity and temperature conversion formulas along with measured values obtained from drilling sites as estimation standards.With the guidance of resistivity ratio and stratification constraints on depth,relevant empirical coefficients were determined.To validate the rationality of our proposed temperature estimation method,we evaluated the effectiveness of inversion results of resistivity derived from audio magnetotelluric sounding profiles,and assessed the goodness-of-fit between measured temperatures at drilling sites and the estimated values.Finally,we performed calculations from resistivity to temperature based on these assessments.The calculated results successfully constructed the underground temperature structure models within areas indicated by two audio magnetotelluric sounding profiles which are then utilized for mineralization prediction.The results of prediction indicate that the high-temperature anomaly zone No.III is consistent with known drilling achievements.Therefore,it iwas inferred that there are four shallow high-temperature anomaly zones(No.I,II,IV,V)and three deep high-temperature anomaly zones(No.VI,VII,IX)in the two profiles;among them,the No.VII anomaly is closely associated with the spatial distribution of fault F4-2 and exhibits an upward migration tendency from deeper regions,suggesting a higher likelihood of reflecting deep thermal reservoirs in this location.The anomalies No.VI and IX are closely linked to fault F4-1 and present new targets for future exploration.The calculation of relevant empirical coefficients in this

关 键 词：谷露地热田 热结构 电阻率 温度结构 高温异常区预测 

分 类 号：TK521.2[动力工程及工程热物理—热能工程] P314[天文地球—固体地球物理学] P631[天文地球—地球物理学]