Acoustic impedance estimation from combined harmonic reconstruction and interval velocity

Low-frequency components of reflection seismic data are of paramount importance for acoustic impedance inversion, but they typically suffer from a poor signal-to-noise ratio. The estimation of low frequencies of the acoustic impedance can benefit from the combination of a harmonic reconstruction method (based on autoregressive models) and a seismic-derived interval velocity field. We propose the construction of a convex cost-function that accounts for the velocity field, together with geologic a priori information on acoustic impedance and its uncertainty, during the autoregressive reconstruction of the low frequencies. The minimization of this function allows one to reconstruct sensible estimates of low-frequency components of the subsurface reflectivity, which lead to an estimation of acoustic impedance model via a recursive formulation. In particular, the method is suited for an initial and computationally inexpensive assessment of the absolute value of acoustic impedance even when no well log data are available. We first tested the method on layered synthetic models, then we analyzed its applicability and limitations on a real marine seismic dataset that included tomographic velocity information. Despite a strong trace-to-trace variability in the results, which could partially be mitigated by multi-trace inversion, the method demonstrates its capability to highlight lateral variations of acoustic impedance that cannot be detected when the low frequencies only come from well log information.