China's largest oil field, Daqing, will slash capital spending in 2017 by 20% from the amount one year earlier, owner PetroChina said late on Dec. 28, even as it looks to keep output steady.

China's oil majors have been cutting output in recent months to rein in spending, with older and inefficient fields like Daqing, in northern Heilongjiang, coming under scrutiny.

Daqing's investment in drilling and ground engineering projects will be reduced by 20%, PetroChina said in a statement on its website.

However, it aimed to boost production by 10% at each operating well and keep output at about 40 million tonnes of oil and gas by 2019. Oil and gas output was about 41 million tonnes in 2015.