Northeast Electric Power Design Institute Limited Company of China Power Engineering Consulting Group, Changchun 130021, China

The geological information and logging data were used as constraints to build a broadband initial wave impedance model. The quasi-linear matrix equation was established by the parametric substitution method, and the mandatory constraint condition was added to the inversion solutions. Moreover, the nonlinear preconditioned conjugate gradient numerical algorithm was adopted to improve the search direction to reduce the condition number of the coefficient matrix and improve the convergence speed. The spatial distribution characteristics of the broadband wave impedance was then recovered from the limited seismic data. The numerical inversion result of the complex velocity model of sand-shale interbeds proves that under the interference of 5% random noise, the velocity model obtained by the inversion can describe the position of the reservoir and the reverse fault. Due to different noise intensity distributions, the absolute velocity values obtained from the inversions of each track have deviations, but the maximum deviation value is only about 5% of the true value. It is further verified that the algorithm is feasible and effective, with high inversion precision and certain denoising ability.