1887
Volume 20, Issue 10
  • ISSN: 0263-5046
  • E-ISSN: 1365-2397

Abstract

Andrew W. B. Siddans, senior geologist, Robertson Geologging, describes the processing and interpretation of an optical televiewer log (OPTV) during a borehole drilled through flagstones in the North of Scotland for the UK Atomic Energy Authority as part of an ongoing geotechnical and environmental site investigation. The borehole-wall image involved in the project consists of rows of 720 pixels, colour-coded as 24-bit triplets. Each row of pixels represents 1 mm depth on the borehole axis and is oriented NESWN around the borehole wall. The nominal diameter of the borehole is 145 mm. Traces of various geological features are recorded on the imagery, among which bedding, fractures and calcite-veins can be identified (Fig. 1). Processing of such imagery aims to identify and label the significant geological features along with their orientation and depth on the borehole axis. Traditionally this is a time-consuming, interactive process. Methods of partially automating and generally easing the burden are discussed in the processing section below. Interpretation of the dips resulting from processing follows the two classic, broad fields of structural interpretation and fracture analysis. Structural interpretation aims to extract formation dip and identify geological structures such as unconformities, folds and faults, from the distribution and orientation of dips assigned to bedding. Fracture analysis aims to identify geometrical sets of fractures/veins, and then estimate variations in mean-dip and frequency within the sets and lines of intersection among the sets, with depth. Methods and results are described in the interpretation section of this article.

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/content/journals/0.3997/1365-2397.20.10.25244
2002-10-01
2022-11-30
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  • Article Type: Research Article
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