China's first deepwater oilfield saw its secondary development project fully commissioned recently, marking a major technological leap for the country in the challenging field of deepwater complex reservoir development and bolstering national energy security, said industry experts.

China National Offshore Oil Corp announced the full commissioning of the phase two redevelopment project of Liuhua oilfield over the weekend, with the activation of the final well on the Haiji-2 platform, Asia's largest deepwater jacket platform.

Located in the Pearl River Mouth Basin, Liuhua oilfield is China's largest offshore reef limestone oilfield in terms of proven geological reserves. Since its initial commissioning in 1996, the oilfield has produced over 20 million metric tons of crude oil, said CNOOC.

The milestone marks a major breakthrough in China's ability to develop complex deepwater oil and gas reservoirs, enabling the nation to exploit challenging deepwater resources and strengthen its domestic energy supply, said Lin Boqiang, head of the China Institute for Studies in Energy Policy at Xiamen University.

The successful full commissioning of Liuhua's secondary phase serves as a vital blueprint. It validates the technical and economic viability of the deepwater jacket platform plus cylindrical floating production storage and off-loading (FPSO) model, paving the way for the scaled development of similar deepwater assets off China's coast, he said.

"This project effectively de-risks future investment in our challenging deepwater oil and gas portfolio, proving our domestic technology can meet world-class engineering requirements."

Driven by technological advancements reshaping global energy demand, deep-sea resources are now viewed as a critical growth engine for the ocean economy, according to a research institute of CNOOC.

The institute highlighted a recent acceleration in marine oil and gas exploration worldwide, establishing deep and ultra-deep-sea areas as strategic reserves for global energy supply.

According to the National Energy Administration, oceans have become high grounds for global energy supply. It is estimated that over 30 percent of oil and 37 percent of natural gas will come from the ocean.

During China's 14th Five-Year Plan period (2021-25), the nation generated 105 million tons of new crude oil production capacity. Offshore output has been the primary growth engine, consistently contributing more than 60 percent of China's total new petroleum production for the past five years, it said.

China's oil and gas industry is entering a new stage of quantitative and efficiency increases alongside green transitioning, securing a more secure and resilient modern oil and gas system while providing a solid guarantee for national energy security alongside stable economic and social development, said Hu Jianwu, deputy director of the NEA's petroleum and natural gas department.

Despite the rapid expansion of clean power, which is increasingly becoming the dominant source of terminal energy, fossil fuels remain essential, serving as the "ballast stone", ensuring energy accessibility and overall system stability, said the administration.

Substantial reserves estimated at 140 million tons remain in the seabed strata, necessitating secondary development to tap into the potential, said CNOOC.

Jiang Junda, general manager of the Liuhua oilfield under CNOOC Shenzhen Branch, said that the current operational success of the project validates the stability and reliability of the technology used for stable oil production and water control in offshore carbonate reef oilfields.

He emphasized that the development model, combining a deepwater jacket platform with a cylindrical FPSO, has proved to be economically effective, providing a viable solution for the scaled, profitable development of similar deepwater oil and gas resources during China's upcoming 15th Five-Year Plan period (2026-30) and contributing to the nation's maritime power strategy.

The secondary development project comprises two oilfields, Liuhua 11-1 and Liuhua 4-1, situated in an area with an average water depth of approximately 305 meters. The project involves 32 production wells.

Since the first batch of wells began operation in September 2024, daily crude oil output has climbed to a record high of 3,900 tons, said CNOOC.