BAGHDAD—State-owned PetroChina says it has acquired a share in a development project of one of Iraq's most promising oil fields from U.S. major Exxon Mobil.

Thursday's statement says Exxon handed over 25 percent of the consortium to the Chinese oil giant in the 8.6-bilion-barrel West Qurna-1 field in southern Basra region. The financial terms of the deal were not disclosed.

In a 2009 deal with Iraq, Exxon acquired a 60 percent stake and Royal Dutch Shell 15 percent, with the rest held by Iraq's Oil Ministry. But in 2011, Exxon infuriated Baghdad by unilaterally signing a deal with the self-ruled Kurdish region to hunt for oil in their region and in disputed territories.

Since then, Exxon has sought to exit the deal so it could focus on the Kurdish region.