In this study we simulate storm-time substorms isolated and periodic ones by using a three-dimensional dynamic ion-tracing model. We follow the transport and acceleration of ions, under the influence of a background convection electric field with a superposed impulsive electric field due to magnetic field dipolarizations, as observed by spacecraft during substorm expansion. We examine the relative influence of O+ and H+ ions originating in the plasma sheet on the ring current development. Maps of the temporal and spatial variations of ion¬ energy densities in the inner magnetosphere are constructed. Initial results suggest that the difference in energization is much more prominent for O+ ions, which have been observed to be preferentially accelerated by substorm-induced electric fields. Multiple periodic substorms have a distinctly cumulative effect on the ring current development, influencing both the earthward penetration and the energization of ions.