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ABSTRACT: Recent Advances in Borehole Imaging Based on the Circumferential Borehole Imaging Log (CBIL)

Walter H. Fertl

The recently introduced Circumferential Borehole Imaging Log (CBIL) is recorded by an acoustic borehole imaging device that utilizes a rotating pulse-echo transducer to scan and provide an image of the entire (360°) circumference of the borehole wall. A transducer rotates at the rate of six times per second and acquires 250 measurements per revolution.

Two key parameters are being measured: the amplitude of the reflected acoustic wave (which corresponds to variations in the rock properties) and the acoustic travel time (which is indicative of the distance from the transducer to the wellbore wall).

The CBIL provides a complete, detailed 360° borehole image in fresh, salt, and oilbased drilling fluids. Applications are manyfold and include: detection and orientation of fractures, vugs, and borehole breakouts (washouts); orientation and correlation of whole cores; sand/shale ratios in thin-bedded intervals; recognition of depositional features (e.g., highly laminated and/or crossbedded intervals); borehole geometry via high-resolution acoustic caliper data; generation of borehole cross sections and synthetic cores, bed orientation, etc.

Field examples illustrate these various applications in detailed reservoir description.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990