Abstract
Summary
A new ultrasonic tool for borehole and casing imaging has been developed based on recent cementation-imaging technology. A rotating ultrasonic transducer scans the borehole at a high sampling rate to provide detailed images of echo amplitude and radius.
A 250- or 500-kHz focused transducer gives high resolution, penetration in heavy mud, and low sensitivity to tool eccentering. The echoes are analyzed by a downhole digital signal processor to optimize the accuracy and reliability of the radius measurement. The measurements are corrected for eccentering, and the image color scales are dynamically adjusted for optimum sensitivity in real time by the surface computer.
Comparisons with electrical imaging tools show that the ultrasonic amplitude measurement tends to respond to lithology indirectly by changes in borehole radius or rugosity. Ultrasonic imaging is unique in making quantitative high-resolution measurements of borehole geometry that are useful for borehole-stability analysis. Examples of automatic hole-shape analysis are shown. The tool can also evaluate internal casing corrosion and detect holes.
Publisher
Society of Petroleum Engineers (SPE)
Cited by
14 articles.
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