Accurate logging-while-drilling (LWD) borehole caliper data are important for drilling, logging and well completion. A single, accurate LWD caliper can greatly minimize risk and improve quality by bringing critical new information to these applications.
Presently, an LWD azimuthal density porosity tool can provide three different hole-size measurements. In addition to an ultrasonic caliper, a neutron-derived and a density-derived caliper have been recently introduced. Each method has different advantages and limitations that are related to the physics of the measurement and environmental conditions. This paper provides an overview of the ultrasonic caliper, the new neutron- and density-derived calipers and also describes the applicability range of each measurement. A method is also proposed to integrate the different techniques in order to form a single, robust and accurate LWD caliper. Examples of the individual and integrated calipers from an azimuthal density porosity tool are presented.