Complex wells, with horizontal wells as the basic features, serve as advanced well-type technologies for the efficient development of complicated oil & gas fields with low-permeability, unconventional, marine, and deep features, and they have attracted a lot of attention in China and abroad. This article first introduces the concept of complex wells and their application scenarios. Next, some important developments in directional drilling theories and technologies for complex wells are sorted out, including rotary steerable drilling technology, magnetic steering drilling technology, and extended-reach drilling technology. At last, the challenges in directional drilling of complex wells are analyzed, and the corresponding suggestions are put forward, so as to provide support for directional drilling of complex wells in terms of theoretical and technical innovations.

Investigating national strategies, scientific frontiers, and industrial development, deep-sea biological research serves to evaluate carbon flux and storage, understand deep-sea ecosystem changes and responses, and explore new deep-sea biological resources at full-ocean depth. Deep-sea environment simulation technology and deep-sea in situ test technology have been developed to observe, detect, and analyze the physiological state, ecological function, and evolution process of organisms in the deep sea and thereby to meet the needs of deep-sea biological research. This paper summarizes the development courses and technical characteristics of deep-sea environment simulation technology and deep-sea in situ test technology, discusses their future development prospects, and proposes development strategies and suggestions to help promote China’s strength in deep-sea technologies and deep-sea bioscience research.