Joint inversion of logging while drilling multipole acoustic data to determine P- and S-wave velocities in unconsolidated slow formations

摘要

We have developed a joint inversion method for LWD multipole acoustic data processing to simultaneously determine formation P- and S-wave velocities. The presence of the LWD tool strongly influences the dispersion characteristics of quadrupole and monopole leaky-P waves, especially in unconsolidated slow formations. We have verified that an equivalent-tool theory can adequately model the LWD multipole wave dispersion characteristics and can therefore be utilized to do forward modeling for the inversion. A major advantage of jointly inverting the multipole data sets, as compared to separately inverting each individual data set, is the reduction of uncertainties in the estimated formation P- and S-wave velocities. We have applied the method to field data processing and validated the processing results.