China’s offshore operator CNOOC Ltd has kick-started a carbon capture and storage (CCS) project at its Enping 15-1 oilfield complex in the South China Sea's Pearl River Mouth basin — the country’s first attempt to apply CCS technology to an offshore field, reducing carbon emissions and boosting recovery.

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The scheme involves building facilities to capture up to 300,000 tonnes per annum of CO2 and rejecting into a vault structure in the reservoir for storage.

Up to 1.46 million tonnes of CO2 will be captured and stored over the life span of the field, which is located 190 kilometres southeast of Hong Kong in water depths of 80 metres.

The project with the magnitude to capture 300,000 tpa of CO2 is equivalent to planting 14 million trees, CNOOC Ltd said.

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Zhang Wei, chief engineer of CNOOC Shenzhen, which spearheads the project implementation, said the scheme involves first separating oil from the CO2 and then dewatering and compressing CO2 before it is rejected into the reservoir.

The Paris-based International Energy Agency in a recent report said that CCS projects being planned worldwide will be able to capture and store 7.6 billion tonnes of CO2 by 2050.

Data from the Global CCS Institute shows that by the end of 2020, there were 65 commercial CCS projects worldwide, which are able to capture and permanently store 40 million tpa of CO2.

Of the total, 26 have started operation, three are under construction, two have suspended operation, 13 are under front-end engineering and design study, and 21 are in the early stage of development. In addition, another 34 are under pilot development as CCS demonstration projects.

CNOOC Ltd chairman Wang Dongjin said that the applying CCS technology to the Enping 15-1 oil complex development is one of the major measures in CNOOC Ltd’s green development initiative.

The Enping 15-1 oil complex includes the development of five fields in water depths between 81 and 98 metres: Enping 15-1, Enping 10-2, Enping 15-2, Enping 20-4 and Enping 20-5.

The project will involve four offshore platforms — a central equipment platform dubbed EP15-1 CEP, a production platform (EP20-4 DPP) and two wellhead platforms (EP10-2 WHPA and EP20-5W HPA ) as well as four subsea pipelines.

A 14-kilometre pipeline will connect the EP10-2 WHPA and EP15-1 CEP platforms, while an 11.1-kilometre line will link the EP20-5 WHPA and EP20-4 DPP facilities.

A 32-kilometre pipeline will then link EP20-4 DPP with EP15-1 CEP from which a 42.2-kilometre line will be installed to transport oil to the existing Hang Yang Shi You 118 floating production, storage and offloading vessel.

Altogether 57 kilometres of subsea cables will link EP15-1 CEP and EP10-2 WHPA, from EP15-1 CEP to EP20-4 DPP, as well as between EP20-4 DPP and EP20-5WHPA.

Power generation facilities will be installed at the EP15-1 CEP and EP20-4 DPP platforms in order to supply electricity to other platforms.

Produced liquids will be sent to the EP20-4 DPP facility for initial processing before being piped to the Hai Yang Shi You 118 FPSO for further treatment.

The floater, which will be retooled to handle additional oil from the Enping 15-1 complex, has been producing fron the nearby Enping 24-2 field since 2014.