Apllication of air underbalanced drilling technology in Xushen21 well

In order to protect the reservoir, to improve the drilling rate in Daqing Oilfield and accelerate the exploration speed in Xujiaweizi Area and to think about the real condition in this part, the air under-balanced drilling technique was used in the section from 2550 to 2918 m of Xushen21 well. During the drilling, air-filled under-balanced drilling technique was applied because of having water in the bottom formation.The air under-balanced drilling footage is 387 m, the ROP is 12.71 m/h, it is 6.5 times faster than the normal; the air-filled footage is 83m;drilling time is 20.4 h; average ROP is 4.07 m/h, and 13.93 days is saved. The experiences of under-balanced drilling is obtained and it can supply some reference to other wells in this area. With the equipments, techniques and drilling parameters got from this well.