Abstract: In the course of drilling and exploration operations in a certain oilfield, the depositional environment and general situation of geological reservoir of such oilfield have been analyzed, the wellbore configuration and wellbore trajectory have been optimized, the sodium-based bentonite slurry has been properly selected, the additives such as tackifier, sodium hydroxide and sodium carbonate have been added so as to increase the dynamic/static shearing force and pH value (higher than 10), and the fully-hydrated bentonite slurry has been drilling deeply to Guantao Group (the vertical depth is about 2 000 m) after the preparation of freshwater . As a result, the quick drilling has been achieved, drilling rate increased from 50~70 m/h to 90~100 m/h, the diameter of upper section has been appropriately increased to reduce the jamming risk in trip/casing running operation, the costs of drilling fluid have been saved, and the typical technology for reducing costs and improving efficiency has been formed in Bohai Oilfield.