西藏谷露高温地热田汞量测量方法应用及试验研究

Application and experimental study of mercury measurement method in Gulu high temperature geothermal field,Tibet

在西藏谷露地热田典型剖面开展土壤汞量测量方法试验研究,对影响因素进行了探讨。结合已有地质认识对谷露地热田热储层进行了定位预测。研究结果表明,汞量测量对于谷露地热田第四系土壤覆盖层下的热异常具有较好的指示作用。试验确定谷露地热田样品采集层位为A层下部细粒土壤,采样深度为20 cm,粒度为-200目。使用RA-915M测汞仪对样品进行测量时,实验确定最佳释汞温度为800℃,载气量为0.2 L·s^(-1),样品重量控制在70~80 mg之间,测试时间为2 min。在适当比例尺条件下开展剖面测量工作,分析提取汞的地球化学强异常,根据异常特征能够有效指示覆盖层下隐伏构造及深部隐伏热流体通道位置,是一种在覆盖区勘查地热资源的有效找热预测方法。

An experimental study on the measurement method of soil mercury was carried out in the typical section of Gulu geothermal field in Tibet.The experimental factors were discussed.A thermal reservoir of Gulu geothermal field was predicted and located with the existing geological understanding.The results showed that the mercury measurement can indicate the thermal anomaly under the Quaternary soil overburden in Gulu geothermal field.The experiment found that the sample collection horizon of Gulu geothermal field is the fine-grained soil at the lower part of layer A,the sampling depth is 20 cm,and the particle size is minus 200 mesh.When RA-915M mercury analyzer is used to measure the sample,the optimal mercury release temperature is 800℃,the gas carrying capacity is 0.2 L·s^(-1),the sample weight is controlled between 70~80 mg,and the test time is 2 minutes.Profile survey carried out at an appropriate scale can analyze the strong geochemical anomaly of extracted mercury.According to the abnormal characteristics,it can effectively indicate the concealed structure and the location of deep concealed thermal fluid channel.Therefore,method of soil mercury measurement is an effective prospecting and prediction method for exploring geothermal resources in covered areas.