Numerical Simulation and Test of Velocity Imaging for Remote Detection Acoustic Logging While Drilling

In order to obtain azimuthal acoustic velocity information of formations around wells and evaluate the heterogeneity of the formations, a well model with different velocities in different directions was designed, and the performance of remote detection acoustic logging while drilling (LWD) in measuring azimuthal acoustic velocity was studied. The well model had four sectors, and the velocities of compressional and shear waves in adjacent sectors were different. In addition, acoustic wave propagation of the well model was numerically simulated, and an eccentric transmitter and an eccentric receiver were adopted for measurement. As a result, waveforms recorded by array receivers were obtained with their azimuth angle of 0°, 90°, 180°, and 270°, respectively. Furthermore, azimuthal acoustic velocity information of formations around wells was extracted from the waveforms, and changes in sectors with different azimuths were identified. According to the parameters of the well model with different velocities in different directions, a test device was designed. The tile-like azimuthal acoustic source was used to accurately measure the acoustic velocity of high-speed media in two sectors, and the acoustic velocity variation trend of low-speed media in the other two sectors was identified. The test results were in agreement with the simulation results. The research showed that it is feasible to evaluate acoustic velocity in different directions by the well model with different velocities in different directions, which provides a theoretical basis for geosteering and formation anisotropy analysis by remote detection acoustic LWD.