Integrated multipole acoustic modeling and processing in general stressed formations, Part 2: A well case study

Stress-induced borehole multipole waveform characterization and processing interpretation are critical for borehole stabilization and hydraulic fracturing development. In the first paper (Part 1), an effective approach was presented to simulate the multipole acoustic responses of a stressed formation. In this second paper (Part 2), the objective is to analyze the shear (S)-wave slowness and anisotropy processing methods for stressed formations using the borehole acoustic logging data from the Mesopotamia Basin, Iraq. An integrated approach for evaluating acoustic slowness and anisotropy is presented. This approach combines a time-domain controlled slowness-time-coherence (TCSTC) method for the monopole logging, waveform inversion and frequency-domain processing methods for the four-component (4C) data from the cross-dipole acoustic logging measurement, to provide an overall assessment of acoustic characteristics around borehole under stress. The results of single depth point and interval data processing demonstrate that the proposed TCSTC can be well applied to the slowness extraction of monopole fast and slow shear waves, especially in the case of fast formation where the slowness of fast and slow transverse waves is difficult to distinguish. Meanwhile, the anisotropy results show that stress-induced S-wave anisotropy results from dipole logging data based on frequency domain processing methods are generally larger than those from dipole and monopole logging data based on time domain methods. Integrating the slowness results of the fast and slow shear waves extracted from the monopole and dipole measurements allows us to assess the velocity variations at radial distances along the borehole under stress, which can be well interpreted using the radial shear-wave velocity profile. A potential limitation of this integration approach is the need for analysis of acoustic multipole logging data, which can be available as part of routine logging measurements. The processing and analysis results can be used as a guideline for understanding and interpreting acoustic measurements in stressed formations.