Abstract: The deep, ultra-deep and unconventional resources have grown to be the major exploration and development fields for increasing reserves and production in China. Since the 13^th Five-Year Plan period, the engineering technology has continuously been researched by focusing on the key exploration and development targets in six basins (including five oil basins and three gas basins) and drilling speed acceleration difficulties, such as high temperature and high pressure formations and narrow fluid density window, and a large number of technical achievements have been obtained. For example, the key drilling and completion technologies for deep, ultra-deep and unconventional horizontal wells have been developed rapidly, forming key technologies with the core of unconventional well structure optimization, safe, highefficiency,optimal and fast drilling, high-temperature resistant drilling fluid, finely pressure-controlling drilling and completion, and expansion pipe, and a number of landmark ultra-deep wells have successfully been drilled; The equipment has been developed such as high-power top drive, integrated geo-steering system, and green economic reservoir reconstruction tool, as well as core additives such as temperature resistance high-performance drilling fluid and high-efficiency leak-proof and plugging materials have been researched, which have accelerated the lowcost,large-scale and cost-effective development of unconventional oil and gas resources. The drilling depth of deep wells exceeds 9000 m, the horizontal section length of horizontal wells is up to 5000 m, and the maximum footage of one trip drilling is 3700 m, with some indicators comparable to those in North America. The research achievements have boosted the discovery and development of large oil and gas fields such as Tarim Fuman, Sichuan Shuangyushi and Daqing Gulong, and provided powerful engineering and technical supports for improving the utilization rate and benefits of resource exploration and development. Associated with the continuous progress of petroleum exploration and development, the engineering geological risks and new challenges faced by drilling operations occur frequently. Therefore, further research is still necessary, including accurate prediction of formation pressure, optimization and expansion of wellbore structure, well trajectory control,high-temperature resistant working fluid system, high-efficiency rock breaking and speed-up tools, as well as integration of geology and engineering, so as to realize the continuous iteration and upgrading of key drilling technologies and equipment, and support the high-efficiency exploration and development of deep, ultra-deep, and unconventional oil and gas resources.