Use, Comparison, Presentation, And Interpretation Of Borehole Image And Acoustic Televiewer Technology

Abstract

Borehole televiewers and image systems are used to accurately show sub surface structural features. The borehole image system can show features not evident with the acoustic televiewer under ideal conditions. Depending on the hole conditions, and the data desired, either the image system or the televiewer may be the preferred instrument. This paper will address: 1. General The operation, calibration, survey setup, and complimentary logs to run with each of these instrument types. 2. Comnarisons The strengths, weaknesses, and similarities of the image system and acoustic televiewer. 3. Data acauisition Data gleaned from surveys can include: fractures and fracture orientation; lithology and lithlogic changes; strike and dips; bedding planes, joint sets, and foliation; compressional, extensional and horizontal stress determination; information on how the borehole was drilled; and orientation of core. Interpretation of this data will be discussed. 4. Presentation and annlication Real examples will be used to show how a geoprofessional would apply this data to varying situations. Data from a range of diverse environments will be included, and various data formats will be presented. Applications for when and type of surveys to run will be investigated. INTRODUCTION Downhole televiewers and image systems were developed to measure structural features in a well bore. A 2-D, or axial, plot is used to represent a 3-D picture of the borehole (Figure 1). The advantage of this type of presentation is the oriented 360 degree view and the ability to measure dips, strikes, and sizes of structural features in the well. Figure 1. Geometric Representation of a Fracture To read a 2-D axial plot, cut down one side of a 3-D cylinder and lay it flat (Figure 1). A dipping feature spanning across the borehole is now a sinusoid in the 2-D format (Barton 1989)‘. The edges of the 2-D plot usually start with a north (acoustic) or a south (visual) orientation. This azimuth proceeds, in even increments, in a clockwise compass manner from the left edge for a 360 degree view at the right edge. The lowest point of the sinusoid is the Plane and Corresponding BIPS Image Log. (Change d* Orientation by 180 Degrees for the Acoustic Log.) nection of dip of a particular feature