Chinese offshore operator CNOOC Ltd has launched a carbon dioxide enhanced oil recovery (CO2-EOR) project in the Yinggehai basin in the northern waters of the South China Sea.

The Ledong CO2-EOR project is the first such scheme offshore China and one of the first CNOOC Ltd will be implementing as it transitions towards decarbonisation.

The company is using carbon capture and storage technology in the mature Ledong 15-1 gas field to optimise production while reducing CO2 emissions.

CNOOC Ltd chief scientist Xie Yuhong said that the project is at the detailed engineering stage and construction is scheduled for completion in the first half of next year.

China’s Chongqing Gas Compressor Factory emerged as front runner in August to supply the CO2 reciprocal compressor module for the Ledong 15-1 production and reinjection platform, after bidding a competitive price of 2.85 million yuan ($410,000) for the contract.

The module is expected to weigh a maximum of 30 tonnes.

The project is designed to reinject and store up to 30,000 tonnes per annum of CO2 into the reservoir which is able to enhance gas recovery by up to 20%, Xie said.

While reservoir fluids in the Ledong gas field in Yinggehai are heterogenous, the natural gas is mainly composed of methane, CO2 and nitrogen.

The field is estimated to contain high levels of greenhouse gas owing to its 25% CO2 content by volume.

Ledong 15-1 came on stream in 2010 and since then the field has produced a cumulative 7 billion cubic metres of gas.

Gas and CO2 are currently piped to an onshore terminal on Hainan island for separation, with the gas being used as feedstock for chemical production.

CNOOC Ltd initially planned to pipe the gas to the nearby Yacheng field but the CO2 levels were too high for it to be an option.

CNOOC Ltd earlier this month commissioned a similar development at its Enping oil complex in the Pearl River Mouth basin in the South China Sea. Facilities are expected to capture up to 300,000 tpa of CO2 for reinjection and storage in a vault structure in the reservoir.

There is no EOR scheme at this project.