二维孔间电阻率成像中钻孔效应  

Borehole effects of two-dimensional cross-borehole ERT

作　　者：王刚[1,2] 周启友[1] 吴世艳[1,3] 凌成鹏[1] 杨磊[1] 

机构地区：[1]南京大学地球科学与工程学院,南京210093 [2]山东农业大学水利土木工程学院,泰安271000 [3]西安市国土资源局,西安710007

出　　处：《地球物理学进展》2011年第1期311-319,共9页Progress in Geophysics

基　　金：国家自然科学基金项目(40771038);国防科工委核废料地质处置项目(科工计[2007]825号)资助

摘　　要：为了定量分析孔间电阻率成像中钻孔大小及钻孔中填充介质对反演计算结果的影响,本文基于建立的三维地电基准模型,首先根据野外的实际情况选取了典型情况下不同钻孔直径大小及不同电阻率特性的钻孔填充介质组合状况设定基准模型参数,然后分别对设定的地电模型进行正演计算合成二维孔间电阻率数据模型,并对获得的数据模型进行反演计算,计算结果表明:在二维孔间电阻率成像中,钻孔和填充介质的存在引起了钻孔附近区域的电位分布异常,形成明显电流优势流路径.在利用传统二维反演代码解译出的电阻率分布图像中存在着不同程度的钻孔效应,钻孔效应的大小与钻孔直径和填充介质电阻率与背景岩层电阻率比值有直接关系,并且随着钻孔直径和电阻率对比程度的增大而增大.The purpose of this stus is to quantitatively analyze the effects caused by the boreholes＇ size and the backfilled materials in the boreholes to inversion of cross-borehole electrical resistivity tomography （ERT）. Fist, based on the built geoelectrical baseline forward model, we select differently combined borehole sizes and backfill materials according to the typical situations in the field and set parameters to the geoelectrical model. Then we forwardly simulate each model to synthesis the two-dimensional cross-borehole electrical resistivity data, meanwhile calaulate each synthetic data model by the conventional two-dimensional inversion code. The calculated results indicate that there is a preferential current flow pathway and distribution of voltages distorted around the boreholes because of the presence of boreholes and backfilled materials during two-dimensional cross-boreholes electrical resistivity tomography （ERT）. As a result, there exist some different degrees of borehole effects in the interpreted electrical resistivity images inversed by the conventional two dimensional code when ERT are performed between two boreholes, and the borehole effects is related to the borehole diameters＇ size and the resistivity ratio of the backfilled material to the native formation, and the borehole effects would become prominent with the increasing borehole diameter and resistivity ratio.

关 键 词：地电模型 孔间电阻率成像 钻孔效应 数值模拟 

分 类 号：P631[天文地球—地质矿产勘探]