China Oilfield Services Limited (COSL) is a prominent integrated offshore oilfield services company based in Sanhe City, Hebei, China. Established in 2001 as a subsidiary of China National Offshore Oil Corporation (CNOOC), COSL offers a wide range of services across all phases of oil and gas exploration, development, and production. The company has a strong presence in regions including Asia Pacific, the Middle East, America, Europe, and Africa.

COSL operates through four main divisions: Geophysical Services, which includes seismic and engineering surveys; Drilling Services, featuring a fleet of drilling rigs for exploration and management; Well Services, providing various maintenance and completion services; and Marine and Transportation Services, managing a fleet of support vessels. The company is recognized for its advanced technical equipment and commitment to quality, health, safety, and environmental standards. In 2022, COSL reported revenues of approximately RMB 42.7 billion, reflecting its significant role in the offshore oilfield services market.