Chevron's fully owned subsidiary Unocal East China Sea will ramp up production in the Luojiazhai and Gunziping gas fields in Southwest China's Chong-qing Municipality, its biggest investment in China, the company said on Tuesday.

The company will use all three of its gas trains, with combined daily outlet capacity of 7.31 million cubic meters of natural gas, after the success of the first stage of the Chuandongbei project, it said.

The development will be carried out in three stages, the first comprising the development of the Luojiazhai and Gunziping gas fields, as well as the construction of the Xuanhan gas processing plant in Southwest China's Sichuan Province.

The field's production commenced with the start of the first train in January, after delays due to discrepancies with partner China National Petroleum Corp (CNPC) over how to develop the technically challenging gas fields.

The two companies signed a 30-year production-sharing contract in 2007, aiming to supply 7.6 billion cubic meters of gas every year.

The agreement granted Unocal a 49 percent interest in the $6.4 billion project and CNPC the remainder.

The Chuandongbei project covers more than 800 square kilometers in Sichuan Province and Chongqing, containing potentially recoverable natural gas resources of 84.95 billion cubic meters.

Sichuan Province consumed 16.6 billion cubic meters of natural gas in 2015, up by 5.5 percent year-on-year.