When it comes to acquisitions, Cnooc says it has three criteria: deals must be opportunistic, good value and not too risky. That its $7.1bn bid for some of BP’s South American assets ticks none of those boxes says a lot about China’s thirst for oil.

Start with value. The smallest of the country’s big three state-owned oil companies is paying $9.10 per barrel of proved reserves, on an enterprise-value basis, including assumption of debt. That seems reasonable, when Cnooc itself is trading at $33. But these are mature, low-returning assets. Pan American made about $3.50 per barrel in net income in the first half, on JPMorgan’s calculations, one-sixth that of Cnooc. Its return on equity was just 3.6 per cent. That is more than the acquirer could earn on deposit at a local Chinese bank, but not much.

As for risk, increasing exposure to Argentina – one of the most hostile regulatory environments on earth – is a radical departure for a company that has spent most of its 38-year history drilling in shallow Chinese waters. Opportunistic? Perhaps; BP won’t be doing this kind of thing often. But this is Cnooc’s fifth big deal of the past 12 months, suggesting a growing impatience in Beijing to secure supplies. Strong production gains without reserve accretion have cut Cnooc’s oil reserve life – proved reserves divided by production – almost in half over the past three years, to 6.4 years. China, as a whole, produced 4.9 per cent of the world’s crude last year, but consumed 10.4 per cent of it. The nation’s aggregate reserve life of