After more than five decades of rapid development, the design and manufacturing technologies of polycrystalline diamond compact (PDC) bits have become mature, and they have become dominant tools for rock cutting in global oil and gas drilling engineering. Currently, oil and gas exploration and development have accelerated in China, and difficult tight rock drilling has become one of the biggest challenges faced by deep and ultra-deep drilling engineering. The dependence on PDC bits featuring long service life and efficient rock cutting is increasing day by day. However, the development of PDC bit technologies in China and abroad has slowed down and seems to have reached a bottleneck stage, without any disruptive technological innovation. The existing bit products in China and abroad fail to meet the drilling needs of depths of more than ten thousand meters, so it is urgent to develop new materials and technologies for efficient rock cutting. This article sorts out the research status of key design and manufacturing technologies of PDC bits, summarizes the drawbacks of bits made in China, outlines future development trends, and proposes corresponding suggestions.

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.