Full-waveform inversion and least-squares reverse-time migration imaging of collimated ultrasonic-beam data for high-resolution wellbore integrity monitoring

摘要

Los Alamos National Laboratory (LANL) has recently developed an ultrasonic side-lobe suppressed Bessel collimated beam transducer for low-frequency imaging through highly attenuating materials. We study the effectiveness of using such a collimated ultrasonic-beam transducer for imaging concrete heterogeneities outside borehole casing for high-resolution borehole imaging and wellbore integrity monitoring. We obtain detailed concrete heterogeneities including a low-velocity zone using ultrasound data acquired with a 3D imaging prototype and our recently developed full-waveform inversion and least-squares reverse-time migration methods. Full-waveform inversion fits synthetic ultrasonic waveforms with recorded waveforms to build a high-resolution velocity model. Least-squares reverse-time migration produces a high-resolution structural image showing material discontinuities. Our results demonstrate that LANL's 3D imaging system with a collimated ultrasonic-beam transducer together with full-waveform inversion and least-squares reverse-time migration imaging has great potential for high-resolution single-well borehole imaging and non-destructive evaluation. Published by AIP Publishing.