Objectives The Dengying Formation gas reservoirs in the Sichuan Basin are characterized by great burial depth, multiple superimposed pressure systems and strong reservoir heterogeneity. During drilling, risks such as the coexistence of kick and lost circulation, borehole collapse and pipe sticking, high temperature and high pressure (HTHP), and sour-gas well control are superimposed, which severely restricts optimized-fast drilling and beneficial production. Methods Taking the Gaoshiti–Moxi block, the Penglai gas field and the Daxingchang block as key objects, five geological and engineering constraints were quantitatively characterized. A casing program design methodology with "accurate formation pressure prediction—efficient safety-window expansion—casing program optimization and extension" as the main line was established. Ten key technologies were developed, covering accurate wellbore pressure control, kick/loss early warning and treatment, ultra-high temperature drilling fluid, efficient rock breaking and ROP improvement, measurement/logging while drilling, ultra-deep liner cementing, high-strength coring, digitalization and well control. A drilling program was further designed and verified for the new Pengshan–Qingshen block. Results A formation pressure prediction model combining the improved variable-exponent Eaton method for sand–mudstone and the Bowers effective-stress method for carbonate rocks was established, increasing formation pressure-bearing capacity by 0.22 g/cm³. A "five-to-six spud conventional plus non-standard" casing program series was developed; the ultra-large-size managed pressure drilling (MPD) equipment achieves a wellhead pressure control accuracy of ±0.07 MPa under a 680 mm main bore and a flow rate of 150 L/s. In the Dengying Formation of the Gaoshiti–Moxi block, the "micro-overbalance with micro-loss" MPD mode reduces mud loss by 81% and complex time by 92.4%. The 260 ℃ oil-based drilling fluid system reaches a maximum density of 2.60 g/cm³, and the JFS PLUS water-based system shortens the horizontal-section drilling cycle by 35.03% compared with oil-based fluid. The self-developed rotary steerable system has accumulated 6 806 m of footage and increased the rate of penetration (ROP) by over 60%. Automatic managed-pressure cementing and the high-strength, high-toughness anti-channeling cement slurry increase the cementing qualification rate by 25%, with over 500 field applications. Conclusions The technology system has been applied in more than 300 wells across three blocks, reducing drilling fluid loss by over 84% and complex loss time by over 81% year on year. It has supported the Asian deepest vertical well record of 9 026 m in Well Pengshen 6 and the 299 d drilling cycle record in Well Dashen 102, providing a reference for safe and optimized-fast drilling of similar deep carbonate gas reservoirs in China and abroad.
Dengying Formation gas reservoir; deep and ultra-deep well; casing program optimization; managed pressure drilling; ultra-high temperature drilling fluid; ROP improvement tool; MWD/LWD; ultra-deep liner cementing; well control safety
Liu G., Dai R., Dong Y.,
Chen L. Drilling Technology Route and Safe Drilling Technology for Dengying
Formation Gas Reservoirs in the Sichuan Basin. Int. J. Eng. Sci. Technol., 2026, 4(4), doi: 10.58531/ijest/4/4/1
