A cement velocity inversion method based on array ultrasonic lamb waves

Abstract

This invention discloses a cement velocity inversion method based on arrayed ultrasonic Lamb waves, belonging to the field of oil and gas well exploration and development technology. It solves the technical problems of low computational efficiency and limited applicable velocity range in cement velocity inversion algorithms. The method includes: performing spatiotemporal preprocessing on the array signal to obtain the target guided wave mode, and extracting the complex dispersion curve of the target guided wave mode; constructing a three-layer planar medium model and deriving the dispersion matrix; setting the acoustic parameters of the well fluid and casing, generating multiple sets of initial value sequences for the parameters to be inverted, and calculating the determinant of the dispersion matrix; constructing a loss function, iteratively updating the parameters to be inverted and repeating the process until the number of iterations reaches a preset iteration threshold; traversing all sets of initial value sequences and extracting the iteration parameters corresponding to the round in which the loss function reaches its minimum value. This invention broadens the applicable working conditions and universality, facilitates automated and batch processing, and improves computational efficiency.

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