They could with the momentum they have, but there's a few problems I think the SLM are considering. First, their victories mostly come from guerrilla (sp?) combat and not the traditional advancement-style warfare. As for the oil, that's a secondary thing. Garang himself doesn't care about freeing the south but the whole country, at least according to his last biography, which was written awhile back so I don't know how accurate that statement is now. He's not the only one in charge now though. It's the corporate decisions (not that Garang's leadership was flawless) which have these other agendas. However, majority of the oil is in the south so they do deserve a majority if not the whole thing.