China Oilfield Services Limited, together with its subsidiaries, provides integrated offshore oilfield services in Mainland China and internationally. The company operates through four segments: Drilling Services, Well Services, Marine Support Services, and Geophysical and Surveying Services. The Drilling Services segment provides drilling, module rigs, land drilling rigs, and drilling rigs management services. As of December 31, 2017, it operated and managed a total of 43 drilling rigs, including 32 jackup drilling rigs and 11 semi-submersible drilling rigs; 3 accommodation rigs; and 5 module rigs. The Well Services segment offers onshore and offshore well services, including logging, drilling and completion fluids, directional drilling, cementing, well completion and workover, stimulation, etc. The Marine Support Services segment owns and operates offshore vessels that provide services for offshore oil and gas fields exploration, development, construction, and production. This segment also offers anchor handling for various water level, towing of drilling rigs/engineering barges, oil lifting, offshore transportation, standby, firefighting, rescue, oil spill assisting, and other marine support services. It operates and manages approximately 130 vessels, including AHTS vessels, platform supply vessels, and oilfield standby vessels. The Geophysical and Surveying Services segment provides offshore seismic acquisition, offshore geo-surveying, seismic data processing and interpretation, and underwater engineering services. It owns five towing streamer seismic vessels, one professional source vessel professional source vessel, two undersea cable team, five integrated marine surveying vessels, and two support vessels. China Oilfield Services Limited also issues bonds. The company is based in Beijing, China. China Oilfield Services Limited is a subsidiary of China National Offshore Oil Corporation.