China has become the biggest single investor in Iraq's oil and gas sector, with nearly one fifth of the reserves that have been auctioned over the past year under its control, Meed has reported. China is spending a total of $577m in signing on fees to give it access to an estimated 24 billion barrels, or about 18% of the reserves on offer, the magazine said, citing its own data. Chinese investment doubles the US' signing on fees, which has committed $296m to control about 12 billion barrels, the magazine added.