Deep and ultra-deep oil and gas well drilling technologies: Progress and prospect

In the period of “13th Five-Year Plan”, domestic deep and ultra-deep oil/gas well drilling technologies were developed quickly and a great number of technological achievements were obtained by means of continuous researches, including: (1) high-end devices, such as automatic drilling rig, managed pressure drilling, logging, cementing and completion technology, high-torque top drive system, and deep-well coiled tubing operation unit; (2) advanced tools, such as vertical drilling tool, non-planar tooth bit, high-strength expandable tubular, high-temperature, high-torque and long-life screw rod, torsion impact tool, synergistic damping based rock breaking tool, measurement while drilling tool, and safety monitoring tool; (3) core additives, such as temperature-resistance high-density oil based drilling fluid, high-performance water based drilling fluid, ductile cement slurry, and self-healing cement slurry; (4) life-cycle wellbore integrity technology system. Nevertheless, oil and gas well drilling and completion still faces severe challenges, including deep (great burial depth), steep (large formation dip), narrow (narrow pressure window), thick (thick gravel layer, salt bed and other complex intervals), difficult (complex multi-pressure system, abundant complex accidents and poor drillability) and high (high temperature, high pressure and high acid). Facing these challenges, the following suggestions are proposed. The key to the oil and gas reserve and production increase during the 14th Five-Year Plan and afterwards is till deep and ultra-deep layers. And it is necessary to focus on above mentioned geological difficulties to research key core technologies, such as automatic and intelligent drilling equipment, ultra-high temperature wellbore working fluid, pre-exploration while drilling and digital twin well construction, so as to realize the iterative upgrading of traditional superior technologies and improve the ability to drill deep and ultra-deep wells safely, quickly and optimally. In conclusion, during the 13th Five-Year Plan, China exceeded America in the number of ultra-deep wells for the first time and its well depth stepped up to a new stage of 8000 m, which plays an important role in supporting the development of deep oil and gas exploration and development and improving the market competitiveness of drilling and completion.