Schlumberger

Technical Paper: New Logging-While-Drilling Azimuthal Resistivity and High Resolution Imaging in Slim Holes

Society: Other
Paper Number:
Presentation Date: 2011
 

Abstract

A new LWD device provides laterolog resistivity and borehole images in slim holes drilled with conductive mud. The tool consists of a laterolog resistivity array combined with an azimuthal orientation system.

The laterolog array consists of monitored button electrodes and toroidal antennas. The buttons are used to acquire focused resistivity measurements, with four different radial depths of investigation. The azimuthal system uses Earth’s magnetic field as a reference to determine the sensor position as it rotates. The resulting borehole resistivity images can be transmitted uphole in real time for optimized well placement and for wellbore-stability applications. A special current configuration in the button electrodes allows estimating the conductivity of the drilling fluid at down-hole conditions. The toroidal antennas also provide bit resistivity and non-azimuthal, axially focused laterolog measurements at two depths of investigation.

An optional sleeve is dedicated to the acquisition of high-resolution images. The sleeve uses an array of button electrodes placed on a removable stabilizer to acquire high-resolution borehole images. The image quality in the depth domain is preserved by an innovative downhole correlation algorithm that avoids most time-to-depth conversion problems.

This paper presents field test results and applications from horizontal wells in Italian gas storage fields.

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