Breakthrough in World-Class Offshore Reef Limestone Oil Field Development Challenges

On September 19, China's first deep-water oil field secondary development project - the Liuhua 11-1/4-1 oil field secondary development project - marked its first year of operation, with cumulative crude oil production exceeding 700,000 tons. The development results have surpassed expectations, marking CNOOC's successful breakthrough in tackling world-class challenges in offshore reef limestone oil field development.

Reef limestone oil fields are recognized as one of the most challenging reservoir types globally for development. Beneath these fields typically lies a massive "water cushion," and once extraction begins, bottom water rapidly advances along paths of least resistance through pores and fractures, causing arbitrary channeling that leads to rapid water flooding of oil wells and prevents the extraction of large quantities of crude oil. After ten years of concentrated research and development, CNOOC has established a series of offshore reef limestone water control and oil stabilization technologies, significantly enhancing the recoverable reserves and recovery rate of the Liuhua 11-1 oil field.

The Liuhua 11-1 oil field is China's first deep-water oil field and remains the largest proven geological reserve reef limestone oil field offshore China to date. Since commencing production in 1996, the oil field has cumulatively produced over 20 million tons of crude oil, but the recovery rate stands at only 12.84%, with approximately 140 million tons of oil reserves still buried deep beneath the seabed.