BBC World Service business correspondent
The untimely death of the South Sudanese leader John Garang in a helicopter crash has re-ignited competition between oil companies.
Oil and power are never far apart as the SPLM realised
Many are keen to develop Africa's most promising untapped reserves.
Garang had ties with a small British company, White Nile, which claims exploration rights to an area which may have up to a billion barrels of crude.
There's speculation his death will strengthen French oil company, Total, which also claims rights over the area.
White Nile's shares fell 12% on Monday following news of Garang's death, even though the company denied operations would be affected.
It is easy to see why investors were nervous. Garang played an important role in a deal that gives White Nile a 60% stake in developing the Block Ba oil concession, a region thought to contain $200bn worth of untapped oil at current prices.
White Nile has only been in business two years. It was founded by a former star of the England cricket team, Phil Edmonds, who developed a strong working relationship with the ex-rebel leader of the Sudan People's Liberation Movement.
White Nile has certainly been popular with British investors - its shares rose more than tenfold in their first month's trading on London's Alternative Investment Market.
The company says Garang's death won't affect its exploration concession as the deal it signed is backed by other high-ranking figures in southern Sudan's semi-autonomous government.
Meanwhile, the French oil giant Total claims to have rights over the same area under a 1980 agreement it signed with the other side in the civil war - the national Sudanese government.
If nothing else, the dispute shows how oil and factional politics have got muddled up in one of Africa's most devastated but potentially wealthy regions.
The peace deal signed in January to end the 21-year-old civil war between north and south has unleashed a new form of conflict.
Chinese firms are now among the main players in a corporate battle over rights to Sudan's oil and mineral riches.