Advanced monopole and dipole sonic log data processing – part 1: real-time
Real-time open hole wireline sonic logging data processing becomes a nontrivial task to accurately, automatically and efficiently evaluate both the compressional and shear slowness of a borehole rock formation when human interaction is not possible and signal processing time is limited to elapsed time between different transmitter firings. To address real-time sonic data processing challenges, we present self-adaptive, data-driven methods to accurately measure formation compressional and shear wave slowness from both monopole and dipole waveforms in all types of formations. These new real-time processing techniques take advantage of the fact that advanced wireline sonic logging tools have wide frequency responses and little to no detectable tool body arrivals. These technology improvements provide an opportunity to implement a first-motion-detection technique that detects the onset of compressional waves in the monopole array waveforms. The knowledge of compressional arrival time and corresponding slowness are then used to project an appropriate slowness-time window in order to identify the monopole refracted shear wave and its slowness based on the range of possible Vp/Vs for earth rock formation. To process the borehole dipole flexural waves, we provide a new, data-driven frequency domain method that enables the evaluation of the full flexural-wave dispersion response and its corresponding low-frequency shear slowness asymptote. Field data processing results show that our methods provide high-quality compressional slowness (DTC) and shear slowness(DTS) measurements that are not affected by other borehole modes or dispersion complications in all formation types.