The depth of detection (DOD), which is an important concept in logging data interpretation, describes the detection capability of the borehole measurements. We extend the definition of DOD for azimuthal information, namely the geosignal delivered by azimuthal resistivity tools, to resistivity logs in logging-while-drilling (LWD) applications. Instead of using the radial geometric factor, the detection thresholds in predicting a geologic boundary is employed to describe the DOD of a measurement. This definition unifies the criteria to evaluate the detectability of different borehole measurements, such as LWD resistivity measurements, and geosignals. It can also be generalized to other kinds of well logging methods in LWD applications. Using the proposed definition, we present the analyses of the detection capability of the LWD resistivity measurements in looking-around and looking-ahead applications. And they provide more tangible descriptions. In vertical or near-vertical wells, the definition provides an indicator to evaluate the capability and reliability of looking-ahead of deep/ultra-deep LWD resistivity tools. The investigations on the influence of the DOD on the distance-to-boundary (DTB) inversion, which can help in developing a robust and accurate inversion scheme, are also presented and discussed
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