Characterization of Cavity Reservoirs Based on a Shape-Constrained Multi-Trace Seismic Inversion Method

Ultra-deep marine carbonate cavity reservoirs in Northwest China are characterized by strong heterogeneity and complex geometries. Conventional seismic inversion methods generate over-smoothed results, blur geological boundaries, and suffer from severe non-uniqueness, making it difficult to accurately identify low-impedance cavity anomalies. To tackle these problems, this study develops a shape-constrained multi-trace seismic inversion method based on the Mumford–Shah functional. To meet the computational requirements, a multi-trace inversion framework is adopted, and the Ambrosio–Tortorelli approximation is introduced to convert the non-smooth Mumford–Shah functional into a solvable smooth form. The proposed method realizes the joint inversion of acoustic impedance and geological interfaces, implicitly encourages piecewise constant regions and preserves sharp geological boundaries, and effectively mitigates inversion non-uniqueness. Numerical experiments and field applications validate that the method delivers high lateral resolution and boundary accuracy even with limited prior information and reliably delineates discrete “string-bead” cavity geometries with high consistency to drilling and logging data, providing a robust solution for fine characterization of complex carbonate cavity reservoirs.