浅析地热井施工中岩性识别与地层划分——以姚家园公园地热井为例

Discussion on the Stratigraphic Division and Lithological Identification in Geothermal Well Construction——Taking Yaojiayuan Park Geothermal Well as an Example

本文通过对姚家园公园地热井钻凿过程中所揭示岩性的现场编录,考虑地质历史时期的构造-岩浆活动,以实验室岩矿鉴定成果和测井曲线梯度电阻率、电位电阻率、放射性指标的变化为佐证,初步确定了揭露地层的地质年代。采用地质与钻探相互佐证的方法,证实姚家园地区地热勘查中岩性的确定、地层的划分是合理的。总结了地热井工程中地层和岩性识别的一般步骤:首先,对岩屑使用野外地质辨别方法,根据岩石色率、硬度、致密性、钻时效率曲线及钻进过程中泥浆的消耗情况对地层进行初步划分;其次,通过对地层分界面和关键点的岩屑取样进行实验室岩矿鉴定,为初步划分提供科学的证据;最后,根据测井曲线中的梯度电阻率,电位电阻率和放射性三项指标的实际变化情况与实验室岩矿鉴定成果的对比,划分出属于不同地质年代和不同岩性的地层。

Based on the on-site lithological cataloging results during the geothermal well drilling process in Yaojiayuan Park, the tectono-magmatic activities at different geological periods, the rock-mineral identification results at laboratory, and the gradient resistivity, potential resistivity, radioactivity recorded on the logging curves, this paper initially determines the geological time for the exposed strata. Using the geological and drilling methods to prove each other, it is confirmed that the lithological identification and stratigraphic division in the geothermal exploration of Yaojiayuan area are reasonable. The general steps for lithological identification and stratigraphic division in geothermal wells are summarized： firstly, field identification methods are used to divide primarily the strata based on rock color index, hardness, compactness, drilling efficiency curve, and mud consumption during drilling; secondly, the rocks and minerals sampled from the lithological interface and key points, are identified at laboratory; finally, the actual changes of gradient resistivity on the logging curves, the potential resistivity and radioactivity are compared with the identification results at laboratory, to confirm the forming time of strata and rocks.