CNOOC Bohai Oilfield: How It Continually Discovers Hundreds of Millions of Tons of Oil and Gas | Tianjin Daily Front Page Headline Today

Reporter | Wang Rui

By the Bohai Bay, drilling towers stand tall; deep in the Cangmingshui, oil and gas surge.

As the main front, base, and hub of Bohai oilfield development, Tianjin has always been a key strategic point for China’s offshore oil and gas exploration and development, bearing the important mission of ensuring national energy security.

The Bohai oilfield is explored, developed, and managed by China National Offshore Oil Corporation Tianjin Branch (hereinafter referred to as CNOOC Tianjin). Recently, a new shallow-layer large discovery was made in the Bohai Sea—Qinhuangdao 29-6 Oilfield. This is the seventh billion-ton-level oil and gas field discovered in the Bohai oilfield since 2019, with proven oil and gas reserves reported to be substantial, further solidifying China’s offshore oil and gas resource reserves.

The Bohai oilfield was established in 1965. Why does this offshore hotbed of oil and gas continually break exploration barriers and frequently report good news, repeatedly discovering large oil fields? The answer lies in the gift of the Bohai Bay Basin, in the pursuit of independent innovation, and in the steadfastness and responsibility of offshore oil workers seeking oil at sea. Every drill bit’s advancement and every technological breakthrough are unlocking underground energy treasures, injecting “deep blue power” into national energy security.

Smartly Breaking “Fragmented Blocks” and Seeking Oil at Sea

The geological structure of the Bohai Bay Basin is complex, like a “plate” shattered and crushed, with scattered reservoirs, fractured shallow structures, and dense deep-layer clastic reservoirs. Undoubtedly, seeking large and medium-sized oil and gas fields in such structures with traditional methods faces severe challenges.

So, how to break the deadlock? Offshore oil workers, after repeated analysis and verification, have taken improving the understanding of the geological differences between marine and land oil as a breakthrough point. From the early exploration stage focused on uplifted peaks to now the detailed exploration phase, they continuously update theories and tackle technical challenges.

Yang Haifeng, Exploration Department Manager of CNOOC Tianjin, said that in natural gas exploration, the research team innovatively proposed the “Bohai Bay Oil-Type Basin Large Gas Field Exploration Theory,” leading to the discovery of China’s first billion-cubic-meter large gas field in Bohai—the Bohai 19-6 Condensate Gas Field. Facing challenges such as small reserves and scattered distribution in shallow oil fields, researchers explored new exploration theories for recent formation lithology reservoirs, enabling the Kengli 6-1 Oilfield to “float” to the surface and laying a resource foundation for increased production.

Rising to the Sea, Moving Toward Oil

On this vast blue land of Bohai, offshore oil workers’ progress has never stopped. The successive discoveries of large and medium-sized oil and gas fields demonstrate the maturity and leadership of China’s offshore exploration and development technology. By 2025, shallow lithology exploration will steadily advance, with large and medium-sized oil fields discovered in the Shijiutuo Uplift, the eastern Bohai South Low Uplift, and the Chengbei Low Uplift; exploration in Paleogene lithology and lacustrine carbonate rocks continues to break through, broadening exploration fields…

Bohai oilfield scientists observe core samples in the core library.

Photo provided by CNOOC Tianjin

In December 2025, a well in the southern Bohai oilfield produced high-yield oil and gas flows. As the most explored and developed area of the Bohai oilfield, the southern region faces urgent needs for reserve replacement in aging fields. Fully leveraging the mature production facilities, integrating old well data, the latest 3D seismic data, and development dynamics, they proposed a new theory of “compression-torsion fault-controlled traps—paleogeomorphology-controlled reservoirs,” discovering high-quality reservoir development zones.

Operators at the Bohai Century platform in Qinhuangdao 32-6 Oilfield are upgrading the boiler system distribution panel.

Photo provided by CNOOC Tianjin

“Not only in the southern Bohai oilfield, but we also strive to achieve breakthroughs across all layers—shallow, medium, and deep—in Bohai exploration,” said Guo Tao, Chief Geologist at CNOOC Tianjin Bohai Petroleum Research Institute. In 2025, Bohai once again set a record for exploration wells, with a record high in 3D seismic data acquisition, and significant new proven oil and gas reserves, with promising economically recoverable reserves.

Focusing on Reservoirs, Striving for Production

Drop by drop, oil flows continuously; vast amounts of natural gas surge with vitality.

After 61 years of exploration and development, Bohai oilfield, as the main battlefield for increasing reserves and production, has achieved breakthroughs in key technologies, continuous discoveries across multiple fields, and accumulated scientific and efficient development experience. However, new challenges for increasing production remain.

On-site workers at Suizhong 36-1 Oilfield conduct maintenance on the oil production tree.

Photo provided by CNOOC Tianjin

Among them, ensuring stable production of old oilfields is fundamental. Zheng Xu, Reservoir Manager at CNOOC Tianjin Production Department, said, “In oilfield production, we supplement formation pressure through water injection, which is key to long-term development. During the 14th Five-Year Plan, Bohai oilfield’s injection and production control strategies have adapted to local conditions, shifting from ‘inject enough water, inject good water’ to ‘inject and produce in coordination.’”

The interview revealed that managing Bohai oilfield starts with well management. Emphasis is placed on rechecking old wells and strengthening management of low-yield, low-efficiency wells. Through refined management, technological innovation and upgrades are driven, new techniques and technologies for increasing well productivity are developed, and good wells are identified, optimal technologies are chosen, and plans are formulated to maximize single-well effects, ensuring steady improvement in production increase efficiency and target achievement.

Refined efforts in well potential tapping are beginning to show results. Facing the grand blueprint of reserve increase and production growth, Bohai oilfield is extending exploration and development into deeper, low-permeability reservoirs.

The huge reserves of offshore low-permeability reservoirs are an important future source of reserve growth and production increase. Li Yanlai, Chief Reservoir Engineer at CNOOC Tianjin Bohai Petroleum Institute, said that Bohai oilfield is proactively planning and conducting technological research to achieve breakthroughs from conventional low-permeability to complex lithology reservoirs, and from conventional fracturing to large-scale reservoir modification. Recently, Bohai built China’s first integrated large fracturing vessel, filling a gap in offshore hydraulic fracturing technology and equipment, better meeting the urgent demand for large-scale exploitation of offshore low-permeability oil and gas resources.

Today, Bohai oilfield has established a comprehensive offshore oil and gas production base covering exploration, development, engineering, and production across the three provinces and one city surrounding Bohai, forming a multi-regional development pattern with mature regional pipeline facilities. This year, Bohai oilfield strengthened infrastructure integration, promoted exploration and development integration, accelerated the conversion of reserves into production in Bohai Bay, and aimed for “whole bay development,” connecting the “reserves, production, and transportation” system nodes.

In the center of Bohai, the Bohai 28-2 South Oilfield. Photo by Wu Di

Drilling towers face the sea, oil and gas nourish the heart.

The exploration journey of Bohai oilfield is endless. Offshore oil workers, with the resilience to “bite hard bones,” are advancing into deeper and more complex oil and gas exploration fields.