Oilfield Glossary
Oilfield Glossary
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variable-density log

1. n. [Formation Evaluation]
A presentation of the acoustic waveform at a receiver of a sonic or ultrasonic measurement, in which the amplitude is presented in color or the shades of a gray scale. The variable-density log is commonly used as an adjunct to the cement-bond log, and offers better insights into its interpretation; in most cases microannulus and fast-formation-arrival effects can be identified using this additional display. In openhole, it may be displayed alongside the sonic log transit-time as a qualitative presentation of the acoustic wave train, and is sometimes used for fracture detection by examination of the chevron patterns given by Stoneley wave reflections (and other wave reflections) at fractures crossing the borehole.