自然电场法与高密度电法联作在西江中下游岩溶区找水中的应用

Application of self-potential and high-density resistivity method to the water exploration in karst terrain of middle-lower reaches of Xijiang River

基于溶洼区浅层岩溶地下水的渗流特性,研究富水岩溶地质结构在地下水渗流作用下引起的自然极化及由此形成的自然电场的分布特征,通过自然电场法与高密度电法联作,利用科研和中国地质调查局地质调查项目中探采结合井位的综合物探结果,探讨以自然电场法为主导、辅以高密度电法等综合物探方法,在西江中下游岩溶石山地区不同水文地质环境中寻找岩溶地下水的成功应用效果与失败的经验教训。研究结果表明,感应类电法(如瞬变电磁法、音频大地电磁测深法、地面核磁共振法、激发极化法、声频大地电场法、甚低频电磁法等)受电网、通信网络等人为电磁场干扰较严重;高密度电法抗人为电磁场干扰的能力较强,信噪比较高,但勘探深度相对较浅,且易受炭泥质灰岩、岩溶矿产等良导电岩矿体的干扰。自然电场法利用岩溶地下水运移引起的富水岩溶地质结构自然极化特征,自然电场异常与动态地下水的补给与运移状态关系较密切,自然电场法与基于探测目的体导电特性的高密度电法联作寻找溶洼区浅层地下水可起到方法互补、相互印证、提高探测分辨率与精度的作用。

Based on hydrodynamic conditions of the shallow karst groundwater seepage,we mainly study the natural polarization phenomenon of geological structures in water-enriched karst induced by the action of groundwater seepage and distribution characteristics of the natural electric field therefrom.By comprehensive prospecting with the combination of self-potential method and high-density electronic resistivity method,we analyse and evaluate the application effect of the combination on the exploration of karst groundwater in different hydrogeological environments of middle and lower reaches of Xijiang River.In this study,we also integrate geophysical prospecting results with the data derived from exploration&production wells in the survey project of hydrogeological environment initiated and supported by China Geological Survey.Study results show that induced electrical methods,such as transient electromagnetic method,audio magnetotelluric sounding method,ground nuclear magnetic resonance method,induced polarization method,sonic frequency geoelectric field method,VLF electromagnetic method,etc.,are seriously affected by electromagnetic fields like power transmission and communication network.The high-density resistivity method shows a strong anti-interference ability and high signal-to-noise ratio.But its exploration depth is relatively shallow,and it is easily disturbed by ore bodies with high conductivity such as charry limestones or karst minerals.The self-potential method is used in the situation of polarization of geological structures in water-enriched karst caused by groundwater migration.Anomalies of the natural electric field are closely related to the groundwater recharge and migration.The complementation of self-potential method and high-density electronic resistivity method in groundwater exploration can contribute to the mutual corroboration of prospecting results,hence improving prospecting resolution and precision.