Big Oil has cast an acquisitive eye on east Africa. Total and Cnoocagreed on Wednesday to buy

one-third each of Tullow Oil’s fields at Lake Albert in Uganda for a combined $2.9bn in cash. The deal is ample reward for the patience of Aidan Heavey, Tullow’s indefatigable chief executive, and brings in the heavy lifters to pick up much of the $10bn likely cost of developing the fields. It also gives China another substantial asset in Africa – the Lake Albert fields are capable of producing 200,000 barrels of oil per day, according to industry estimates.

The deal illustrates the pitfalls facing oil companies in exploring and producing in east Africa. The rewards can be huge, as Tullow’s investors should be happy to acknowledge, but they may be less than the headline figures suggest.