Oil has been part of the negotiations with the South and now with the Darfuri rebels. Several Western companies had pulled out because of the civil war and protests over gross human rights violations in the past.
Currently Sudan pumps several hundred thousand barrels per day. I think the hope is that they can double that by opening up reserves in the South and the West. China has a concession for reserves in Darfur. I've read that they have about four thousand troops guarding the pipeline to Port Sudan. There's a map here showing the pipeline:
http://www.eia.doe.gov/emeu/cabs/sudan.htmlThe main threat to the pipeline at present comes from rebel groups in the East, like the Free Lions and the Beja Congress. Sudanese officials have accused Eritrea of sponsoring these groups and, indeed, sponsoring the Darfur rebellion. The latter charge is most probably baseless, although there has recently been an agreement reached between the Free Lions and the Justice and Equality Movement, which is the smaller of the two main rebel groups in Darfur. Eritrea's position is that the government of Sudan is adept at creating hostility North, South, East and West, and should look to its own failures before pointing fingers at its neighbors.
In the last UN resolution, the US proposed sanctions on Sudan's oil industry, which is a primary source of revenue for the armaments and mercenary forces it is using in Darfur. China was opposed to any language concerning oil sanctions, but caved in at the last minute under pressure from Kofi Annan and the US Ambassador Danforth. China has explained their opposition as just business, but they may also feel a strategic interest.
Malaysia also has a concession and is very much opposed to any change in the status quo. More than any nation, including Arab League nations like Saudia Arabia and Egypt, Malaysia has defended the government of Sudan and repeated its position on the Darfur conflict. I don't think they're ignorant of the truth. They would seem to believe that the government can attain peace and stability by wiping out millions of its citizens.
Of course there is much cynicism regarding US motives in Sudan, both popularly and at a ministerial level. Personally I don't find the conspiracy theories to be very credible, because it's not that much oil, and for the resources that are being spent, there are much safer, much more lucrative investments. When the DoD takes the lead on Sudan policy, then I'll start to wonder.