This paper proposed new three time-lapse AVO inversion algorithms: 1) total inversion of the differences, 2) inversion of seismic difference only and 3) sequential reflectivity-constrained inversion. The proposed methods were implemented using synthetic data that simulate a time-lapse model of a heavy oil reservoir. Elastic physical parameters of the time-lapse model were chosen to represent reservoir conditions at pre-production and post-production periods after reservoir depletion.