Schlumberger

UBI Ultrasonic Borehole Imager

Advanced borehole imaging with 100% coverage in oil-base mud

The UBI ultrasonic borehole imager lets you analyze fractures and the stress regime and conduct borehole stability studies using images with 100% borehole coverage. Your structural interpretations are not influenced by mud type, with full acoustic imaging capability in nonconductive, oil-base muds. Two modes of image resolution are available for the UBI imager; the higher resolution measurements deliver an accurate borehole cross section for deriving borehole stability and breakout information.

Accurate amplitude and transit time

The two operating frequencies for standard and higher resolution images from the UBI imager measure both amplitude and transit time. The processing technique avoids cycle skips and reduces echo losses. Image resolution is selected to correspond to the logging environment, such as mud type and density. The higher frequency yields higher image resolution. The lower standard frequency gives a robust measurement in highly dispersive muds.

Sensitivity to surface variation in the borehole wall

Because the UBI tool measures attributes of ultrasonic waves reflected at the borehole wall, the rugosity of the borehole wall can dominate the reflection amplitude. Images from the UBI tool are strongly sensitive to surface variations in the borehole wall but not to variations in lithology. Formation changes are normally seen on the images only if corresponding borehole surface effects, such as changes in rugosity or hole diameter, are present.

The sensitivity of the measurement in combination with 100% circumferential coverage makes the UBI imager useful for detecting drilling-induced fractures, improving fracture analysis in oil-base mud, determining borehole stability, diagnosing the severity and orientation of keyhole wear, identifying borehole breakouts and shear sliding, determining horizontal stresses, and analyzing hole shape.

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Rotating Transducers Sized for Optimal Imaging Standoff

Figure 1. The rotating transducer subassembly is available in different sizes to provide optimum standoff from the casing or borehole wall.
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