China Oilfield Services Limited (COSL) is an offshore oilfield services company in the CNOOC group that works for operators offshore China and in a growing number of overseas markets. It is listed in Hong Kong and Shanghai and organises its work into four divisions that together cover the exploration, development and production stages of an offshore field.
Four service divisions
The divisions are drilling services, well services (described by the company as its technology segment), geophysical acquisition and surveying, and marine support vessels. Drilling covers jack-up and semi-submersible operations, liftboats and accommodation units, with recent emphasis on deep-water and deep-layer wells. Well services span directional drilling, logging, drilling and completion fluids, cementing, workover, well completion and production optimisation, and the company also markets integrated drilling, completion, workover and abandonment packages and unconventional resource services. The geophysical segment runs seismic acquisition and geotechnical surveying, while the marine division supplies support vessels to offshore installations.
Fleet, vessels and equipment
The company profile page states that COSL operates 36 jack-up rigs, 12 semi-submersibles, six module rigs and three accommodation rigs, a total of 57 platforms, supported by 130 working vessels, 13 seismic survey ships and more than 430 units of logging, directional drilling, drilling-fluids, cementing and workover equipment. Among its proprietary tools are the DRILOG logging-while-drilling system and the WELLEADER rotary steerable drilling tool. In 2025 COSL reported double-digit year-on-year growth in drilling rig operating days, which it attributed to deep-water and deep-layer capability and to expansion into overseas markets including South America, and in the first half of 2026 it said utilisation of its overseas semi-submersible rigs stayed high.
Where COSL works
The bulk of the business is offshore China, where the company supports CNOOC's reserve growth and production enhancement programmes. The company states that its services reach beyond offshore China and the Asia-Pacific to Southeast Asia, the Middle East, the Americas, Europe and Africa, covering more than forty countries and regions. Overseas work has been shifting from single technical services towards an integrated model, and the marine support division has been reallocating vessels between domestic and international markets and adding clean-energy vessels. In seismic acquisition, the first half of 2026 release records China's first joint acquisition operation using the company's Haijing system and Haimai equipment.
Results and credit rating
For the year ended 31 December 2025, announced on 24 March 2026, COSL reported revenue of RMB 50.28 billion, up 4.1% year on year, total profit of RMB 5.11 billion, up 9.6%, and net profit of RMB 4.06 billion, up 19.4%. In the six months to 30 June 2026 revenue was RMB 23,787.4 million, 2.0% higher year on year, and total profit rose 4.0% to RMB 2,676.0 million. On 17 September 2026 the company announced that Moody's Ratings had affirmed its A3 issuer rating and baa3 baseline credit assessment and raised the outlook from stable to positive, and had also affirmed the A3 rating on the guaranteed senior unsecured notes issued under its euro medium term note programme by COSL Singapore Capital Ltd.
Listing and shareholder information
COSL has been listed on the main board of the Hong Kong Stock Exchange under code 2883.HK since 20 November 2002. Its American Depositary Receipts, ticker CHOLY, were authorised for Level I unlisted trading on 26 March 2004, and its A-shares began trading on the Shanghai Stock Exchange under 601808.SS on 28 September 2007. Investor relations contacts are published for both Beijing and Hong Kong, and the Chinese registrar details for the Tianjin-registered company appear in the site footer.
Safety, quality and contact
COSL states that it is certified to the International Safety Management code and operates a QHSE management system certified by DNV, with compliance to ISO 9001, ISO 14001 and OHSAS 18001; the website carries policy, management system and good practice pages under its QHSE section, and the company received a best social responsibility award from the China Energy Gas Association in March 2026. General investor enquiries are directed to [email protected] and business enquiries to [email protected] from an office address in Beijing.