PetroChina, the country’s largest oil and gas producer, has agreed to buy a 25 per cent stake in Iraq’s West Qurna 1 oilfield from ExxonMobil of the US, in a deal that cements the dominant presence of Chinese energy groups in Iraq’s oil sector.

Exxon will also sell a 10 per cent stake to Indonesia’s Pertamina, bringing its total interest in West Qurna 1 down from 60 per cent to 25 per cent – though it will remain operator of the field. Royal Dutch Shell’s stake remains unchanged at 15 per cent with Iraqi state entities owning the rest.

Exxon’s relationship with the Iraqi government soured in 2011 when it signed six contracts to explore for oil in Iraqi Kurdistan without Baghdad’s approval. The central government considers such contracts illegal.