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 Acquisition and Surveying Services. The Drilling Services segment provides jack-up drilling rig, semi-submersible drilling rig, module rig, and land drilling rig services. As of December 31, 2020, it operated and managed 57 drilling rigs, which include 43 jack-up drilling rigs and 14 semi-submersible drilling 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 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 140 vessels, including AHTS vessels, platform supply vessels, and oilfield standby vessels. The Geophysical Acquisition and Surveying Services segment provides offshore seismic acquisition, offshore geo-surveying, seismic data processing and interpretation, and fundamental construction services. This segment owns 5 towing streamer seismic vessels, 1 professional source vessel, 2 ocean bottle cable teams, 5 integrated marine surveying vessels, and 2 support vessels. China Oilfield Services Limited also issues bonds. The company is based in Sanhe, China. China Oilfield Services Limited is a subsidiary of China National Offshore Oil Corporation.