The Chinese National Petroleum Corporation's providing capital, technology and expertise for the pile-driving at the Higlieg oilfield on the border between north and south Sudan.

Rosie Sharpe from the environmental rights group Global Witness say that means the north and south will have to cooperate.

If war broke out, it would probably be fought in the disputed oil fields in the borderlands between north and south: in southern Kordofan, Abyei, Unity and the Upper Nile states (see map).