Abstract: During the 14^th Five Year Plan period, China National Offshore Oil Corporation (CNOOC) focused on independent technological innovation in drilling and completion. Through theoretical research and key technological breakthroughs, CNOOC overcame multiple core technical problems and successively broke through key technologies such as deepwater complex oil and gas field drilling and completion, offshore complex structural well drilling and completion, offshore well seismic fusion engineering geological risk identification technology, offshore complex oil and gas field flow safety guarantee technology, integration of geological drilling and production of medium and deep coalbed methane, and digitalization and intelligence of offshore drilling. CNOOC developed key equipment such as deepwater localized underwater production system, intelligent downhole engineering parameter real-time measurement tool, deepwater electro-hydraulic composite intelligent completion tool, composite vibration cementing tool, etc., helping to achieve high-quality development of China's offshore oil industry. In the future, China National Offshore Oil Corporation's front line of building a maritime power and continuously increasing reserves and production. It will continue to make efforts in key core technologies and make greater contributions to safeguarding national energy security.