TABLE OF CONTENTS The borehole televiewer (BHTV) produces an acoustic picture with a rotating ultrasonic transducer or scanner (Zemanek et al, 1969). The transducers can be focused or unfocused. Typically they rotate 3 to 16 times per second. The transducers frequencies range between 200 KHz and 1 MHz. The log inspects the borehole and evaluates the formation as it reveals induced and natural fractures, vugs, distribution of perforations in casing, and casing failures. Table 3 1 shows a summary of characteristics of borehole imaging devices including the borehole televiewer and the formation micro-scanner discussed later.
| Characteristic | Borehole Televiewer | Formation MicroScanner | |
|---|---|---|---|
| Typical logging speed | 800 ft/hr (245 m/hr) | 1600 ft/hr (490 m/hr) | |
| Borehole wall coverage | Full (360 ) | Partial (depending on number of pads and runs) | |
| Borehole size | 6 12 in. (15 30 cm) | 6 18 in. (15 46 cm) | |
| Borehole muds | Best results in light muds | Conductive muds only | |
| Typical Sampling Rates: | |||
| Vertical | 0.2 0.5 in. (5 12.5 mm) | 0.1 in. (2.5 mm) | |
| Horizontal | 0.1 in. (2.5 mm) | 0.1 0.2 in. (2.5 5 mm) | |
| Properties influencing measurement | Acoustic impedance contrasts; borehole geometry | Rock microresistivity | |
| Shortcomings | Sensitive to borehole rugosity and drillmarks; sensitive to tool eccentering and borehole ellipticity | Resolution decreased by pad stand-off; irregular tool speed causes layer misalignment | |
| Main applications | Fracture detection (orientation); borehole geometry; breakout detection (orientation) | Bedding types; fracture detection (orientation and width); fault detection (orientation) |
Figure 3 13 presents a BHTV of a Spraberry (Texas) well. One readily concludes that the well has a...
