钻孔摄像技术的发展与现状

REVIEW OF BOREHOLE CAMERA TECHNOLOGY

基于光学技术的钻孔摄像设备能以照相胶片或视频图像的方式直接提供钻孔孔壁的图像。全景技术的实现使同时观测360°钻孔孔壁成为可能,而数字技术的应用则提供了形成、显示和处理这些图像的能力。所有的图像不仅可用于定性地识别钻孔内的情况,而且还可准确地获得相关的数据并进一步从事定量分析。钻孔摄像技术具有广阔的应用,主要包括岩土工程、工程地质、土木工程、石油工业、采矿工程、冰川研究等诸多方面。据此,全面地回顾了钻孔摄像技术的发展历史和当前的现状,描述了在各个阶段出现的设备技术特征,对数字光学成像系统的原理、光源设计、图像处理和精度进行了对比,给出了以单环技术和图幅技术为定义的数字光学成像系统,最后讨论了钻孔摄像技术将来的发展方向。

Borehole cameras are devices based on optical techniques to provide direct images of boreholes in the form of film or video. Advent of the panoramic technique led to viewing the entire section （360°） of the borehole wall, which is a panoramic image including current depth and compass direction. Digital technique, however, has been utilized to provide a powerful capability of forming, displaying and processing the images. The typical images are the unrolled image and the virtual 3D coregraph. All the images can be used not only to reveal the conditions in the borehole for qualitative identification but also to obtain pertinent information, especially for dip direction, dip angle and aperture of a crack, for quantitative analysis. The borehole camera technology has a wide application to geotechnique, engineering geology, hydraulic and civil engineering, petroleum industry, mining engineering and study on glaciers, etc.. The historical and current development status of the borehole camera technology（BCT） on technology and application are reviewed; and the technical features of devices in each stage, especially for the most representative system of development of the BCT-DBOT（digital borehole optical televiewer）are described. The comparisons of different devices for imaging principle, design of special light source, image processing, image display, image accuracy, etc. are studied; and the digital borehole optical televiewers （DPBCS, OPTV, OBI- 40） are widely used in world according to different image processing methods, i.e., ring by ring method and picture by picture method are distinguished. The merits and shortages of the two methods are illustrated; and the strength and potential development of the borehole camera technology are discussed.