CNOOC Ltd has achieved full-scale operations at its Liuhua 11-1/4-1 oilfield secondary development project in the South China Sea. Since production commenced in September of the previous year, daily crude output has reached a record high of 3,900 tonnes (28,885 barrels).

Project Scope and Infrastructure

The secondary development encompasses the Liuhua 11-1 and Liuhua 4-1 oilfields, situated at an average water depth of 305 meters. The project involved commissioning 32 development wells. It utilizes the deepwater jack-up wellhead platform Haiji 2 and the cylindrical floating production, storage and offloading vessel Haikui 1 (Sea Anemone 1). The Haiji 2 platform processes liquids from both fields, after which crude is transported to the Sea Anemone 1 vessel. To date, 25 shipments of preliminarily processed crude oil have been delivered to onshore refineries.

Field History and Significance

The Liuhua 11-1 oilfield, commissioned in 1996, has produced over 20 million tonnes (147 million barrels) of crude oil to date. It is China's offshore reef limestone oilfield with the largest proven geological reserves, with an estimated 140 million tonnes (1 billion barrels) of reserves remaining. Developing these deepwater reef limestone reservoirs has historically presented significant technological challenges.

Technological Innovations

To overcome these challenges, CNOOC developed four new extraction processes and two novel construction methods, pioneering a technical system for stabilizing oil and controlling water in offshore reef limestone formations. This innovation has significantly reduced the water cut in development wells compared to design specifications. The result is a substantial boost to the field's recoverable reserves and recovery rate, extending its operational lifespan by an estimated 30 years.

Ownership and Broader Context

CNOOC Ltd holds a 100% operated interest in the project. Subsea installations were completed by China's Offshore Oil Engineering Company (COOEC). The project contributes to China's deepwater oil and gas production, which state media estimates has surpassed 12 million tonnes of oil equivalent to date. Peak production from the Liuhua secondary development is expected to reach about 17,900 barrels of oil equivalent per day in 2026.