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Imaging of cased-hole structures using reverse time migration based on ultrasonic pitch-catch measurements
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 84th EAGE Annual Conference & Exhibition, Jun 2023, Volume 2023, p.1 - 5
Abstract
Summary
Cement bond evaluation is of great significance in oil/gas development, geothermal production and CO2 storage. The ultrasonic pitch-catch measurement exhibits poor performances in determining the cement-formation interface due to weak third interface echo (TIE) in non-axisymmetric complex ultrasonic environments. To deal with this issue, we proposed a reverse time migration (RTM) approach for ultrasonic pitch-catch measurements to image the cased-hole structure especially the annulus-formation interface. To further enhance the feasibility of cased-hole RTM, a phase-shift interpolation technique is applied to reconstruct ultrasonic array waveforms from limited receivers in the pitch-catch measurement. Zero-lag cross correlation imaging condition, source-side illumination and Laplace filtering is applied to provide the image with high accuracy and less imaging noises. Case studies of a synthetic well with tool eccentering and a full-scale calibration well demonstrate that the proposed method is able to recover the true position and geometry of annulus-formation interface when it has an irregular shape given with a reasonable migration velocity model.
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