岩溶含水介质充填水和泥识别的地球物理勘查技术探讨

岩溶含水介质中充填物性质(水或泥)的正确识别是目前制约岩溶水有效勘查与开发利用的主要“瓶颈”之一。充填物为泥或水时,均反映为低电阻率特性,无法区分充填物到底是水还是泥,从而往往造成打井的失败。作者在近几年岩溶区地下水地球物理勘查工作初步发现,利用水和泥的极化差异识别含水介质充填物性质具有较大的可行性。本文分别讨论了具有与水和泥极化特性相关的核磁共振找水法、激发极化法、频谱激电法三种物探方法识别含水介质充填水或泥的基本原理、野外试验效果。当岩溶含水介质充填水时,核磁共振找水法就会有核磁共振(NMR)信号反映,激发极化法中的极化率参数、频谱激电法中的时间常数均具有高值特征;当岩溶含水介质充填泥时,NMR信号无反应,激发极化法中的极化率参数、频谱激电法中的时间常数均具有低值特征。上述结论经几个不同类型的含水介质实例得到验证,效果明显。 

Geophysical prospecting techniques in discriminating the in filled water from mud in karst water-bearing media

Correct discriminating the properties of infillings (water or mud) in karst water-bearing media is one of the main “bottle necks” for effective exploration and development of karst water. Both mud and water media are reflected as low resistivity characteristics. So, it is difficult to distinguish whether the water-bearing medium is the water one or the mud one, which often leads to failure in drilling wells. Based on the groundwater geophysical exploration in the karst area in recent years, it is found that it is feasible to identify the water-bearing media with the polarization difference of the water and mud. The basic principle and the field test results with three geophysical methods, the nuclear magnetic resonance method, the induced polarization method, and the spectrum induced polarization method, to identify the water-bearing media filled with water or mud are discussed respectively in the article. If karst aquifer medium is filled with water, there will be a nuclear magnetic resonance (NMR) signals, and a high time-constant value features both tested by induced polarization method and by spectrum induced polarization method. If karst aquifer medium is filled with mud, there is no NMR signal response, and a low time-constant value features both tested by induced polarization method and by spectrum induced polarization method. The above-mentioned conclusions are verified by several cases in different types of media.