前视井下电视和数字钻孔摄像在工程中的应用

AXIAL DOWNHOLE TV AND DIGITAL OPTICAL BOREHOLE IMAGING AND THEIR ENGINEERING APPLICATIONS

利用前视井下电视和数字钻孔摄像,分别从前视和侧视对整个钻孔的360°孔壁进行连续摄像;通过图像特征对孔内现象进行定性描述和定量分析,发现其具有高分辨率、高井壁覆盖率和直观可信等特征。根据两种技术在地质现象、工程活动、溶蚀及破碎带观察等方面的应用结果,总结各自的优缺点和适用范围,发现二者互补性较好。在比较数字钻孔摄像与钻探、电磁波CT、弹性波声波等其他钻孔测试手段的优缺点后,提出充分发挥数字钻孔摄像对钻孔观察的高精度和全孔覆盖率等特点,同时利用电磁波CT的孔间地层延伸测试结果,对地质构造(如破碎带)在钻孔群间的发育情况进行三维空间上的分析。数字钻孔摄像可生成任意长度的孔壁图像,解决了前视井下电视的图像表现深度不可变的问题,可为其他钻孔测试手段资料解释提供佐证。用数字钻孔摄像孔壁展开图上破碎区域面积占图像总面积的百分比可定量描述破碎程度。在较破碎段孔壁展开图像上计算面积,发现图中完整区域与占全图的面积之比与基于岩芯长度之比的岩芯采取率相近。

Utilizing axial view downhole TV（ATV） and digital panoramic borehole camera system（DPBCS）,continuous images of 360°borehole wall are obtained from forward-looking and side-looking,respectively.Through the qualitative description and quantitative analysis of borehole phenomena with the images which acquire downhole with borehole optical imaging technology,it is found that these images have characteristics of high resolution,high wall coverage of and visual credibility.Based on the research and application results of geological phenomenon,engineering activity,solution and fractured zones observation,their individual characteristics and applicability are summarized;and these two methods are proven to have good complementary contribution to logging.By comparison of the individual characteristics with other geophysical methods such as borehole imaging,drilling data,electromagnetic wave tomography and elastic sound wave,a combined analytical way to utilizing the 100% coverage of wall and high resolution images by digital borehole imaging is proposed,utilizing the strata extend data in hole-hole section by electromagnetic wave CT and proceeding the three-dimensional developmental condition about the geological structure（as fractured zone） in boreholes.The DPBCS can provide image evidence for other geophysical method for the wall interval images are variable whereas the wall length of ATV images is fixed.The quantitative description of fractured zone with borehole wall unrolled images was studied;it is indicated that the percentage of image area is also applicable for fractured zone grading.The percentage of integrity area in the wall unrolled image area with fracture area is subtracted from which is close to the total core recovery（TCR） based on core length percentage.