Broadband Acoustic Impedance Building via the Fusion of Sparsely Promoted Reflectivity and Background Acoustic Impedance

Geophysical exploration is developing from qualitative seismic imaging to quantitative imaging, and broadband acoustic impedance is the core. Directly estimating broadband impedance using full-waveform inversion is a strong nonlinear problem. It is difficult to obtain a reliable result in practice. We proposed an alternative way: estimate background velocity, density, and broadband reflectivity first and then fuse them to be the broadband impedance by information fusion. This article studies the method of fusing band-limited reflectivity and background impedance. Due to the observation with band-limited seismic wavelet, only band-limited reflectivity can be obtained even after a lot of processing. The band-limited reflectivity can lead to oscillation error in impedance. Different from the conventional poststack impedance inversion, this article introduces an iterative process without the need of wavelet extraction. Start from the broadband reflectivity that has been subjected to fidelity imaging, least-squares migration, and magnitude calibration. In order to reduce the oscillation error, reflectivity is sparsely promoted such that the reflection coefficients from large to small are gradually fused with background impedance. Reflectivity and impedance are mutually constrained and iteratively updated, and lateral continuity is incorporated. Numerical experiment and 3-D field data application demonstrate the effectiveness of the method. Impedance shows higher interpretability than reflectivity.