Schlumberger

ARI Azimuthal Resistivity Imager

Quantitative azimuthal resistivity imaging with deep directional measurements beyond the invaded zone

The ARI azimuthal resistivity imager makes 12 directional measurements around the borehole circumference with a higher vertical resolution than previously possible from conventional laterolog tools. Using azimuthal electrodes incorporated in a dual laterolog array, the ARI imager provides deep oriented resistivity measurements in addition to standard deep and shallow resistivities. The depth of investigation of the deep oriented measurement can access the virgin formation, beyond the invaded zone, and the sensitivity of the ARI imager’s measurements to azimuthal heterogeneities identifies anomalous resistivity conditions and discriminates between shallow and deep features. A very shallow auxiliary measurement provides data to fully correct the azimuthal resistivities for borehole effects.

Thin-beds and horizontal wells

By providing resistivity logs and images at a vertical resolution of less than 1 ft, logging with the ARI azimuthal resistivity imager is particularly effective in combination with the IPL integrated porosity lithology toolstring for thin-bed analysis.

Because the resistivity measurement is directional instead of azimuthally averaged, it is not by default primarily influenced by the beds that are parallel and close to the borehole. To address this typical logging concern in horizontal wells, the most representative reading can be selected from the deep azimuthal resistivity measurements.

Complementary imaging

Images from the ARI imager complement image logs from the UBI ultrasonic borehole imager and the FMI fullbore formation microimager because of the tool’s sensitivity to features beyond the borehole wall and its lower sensitivity to shallow features. By flagging the azimuthal heterogeneities, the resistivity images from the ARI imager avoid misinterpretation that could occur with an azimuthally averaged resistivity log.

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Deep Azimuthal Resistivity at a High Vertical Resolution

Deep conductive invasion example showing that the LLHR curve has a depth of investigation similar to that of the LLD curve and a vertical resolution approaching that of the MSFL curve.
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