多孔对电磁波CT剖面拼接的影响因素及拼接方法

The Impacting Factors of Multi-hole on Electromagnetic Wave CT Image Splicing and Splicing Approachess

井间电磁波CT是高效探测地下介质电磁特性的地球物理方法,近年来其相关的研究工作很多,主要集中于单孔对反演理论研究;实际工作中常常要在同一个工作区完成几对钻孔乃至几十对钻孔的电磁波CT成像测量,单孔对成果解释往往不能满足要求,而直接将单孔对剖面进行首尾连接,在共用孔位置的成像结果往往不吻合。基于上述问题,首先从理论上对反演方法、初始场强两个主要影响因素进行了分析,然后提出采用反距离加权的局部多项式拟合插值法对成果数据进行处理,实现了多孔对电磁波CT剖面拼接;最后将上述方法应用于贵州某岩溶勘查项目。结果表明,该方法能够很好地消除共用剖面处等值线不连续的现象,其结果与原单孔剖面的拟合度高,并且可以准确地识别近直立异常以及有一规模的水平异常上,对提高电磁波CT综合解释效果具有实际应用价值。

Cross-well electromagnetic wave computed tomography(CT) is a geophysical method to efficiently detect the electromagnetic characteristics of underground media.In recent years,many related application cases focus mainly on the theoretical research of single-hole-pair inversion.In practice,it is usually necessary to perform electromagnetic wave CT measurements at several to dozens of pairs of boreholes in the same working area.Single-hole interpretation usually could not meet the requirements,in which a single-hole image is connected directly to the profile head to tail.Therefore,the results do not match well on both sides of the shared hole.In order to solve image match problems,the authors analyzed the two dominant impacting factors,namely the inversion method and the initial field theoretically at first,then used the inverse distance weighting local polynomial fitting interpolation method to process the CT results,realizing the multi-hole to electromagnetic wave CT image splicing.The new method was applied to a karst exploration project in Guizhou.The results indicate that it can effectively eliminate the discontinuities of contour lines at the shared profile and has a high degree of fitting with the original single hole profile.Moreover,breakthroughs have been made in identifying near vertical anomalies and large-span horizontal anomalies,improving the comprehensive interpretation effect of electromagnetic wave CT.