Abstract: The extended reach wells in Southern Sulige Block have average total depth of 3 900 m and average horizontal displacement of 1 200 m. Their rate of penetration (ROP) is restricted seriously due to the technical difficulties in the process of construction, e.g. deep well, large displacement, difficult trajectory control, and poor formation drillability. In regard of this, a series of key drilling technologies for the efficient drilling of extended reach wells in Southern Sulige Gasfield were developed from the aspects of profile design optimization, trajectory control, bottom hole assembly (BHA) and bit and screw rod selection. They include " vertical-buildup-angle holding-slight drop” profile, " two-trip drilling” trajectory, " four-in-one” BHA with strong angle holding capacity, and bit and screw rod suitable for fast drilling in this block. Owing to the application of these key technologies, the average drilling cycle in 2017 is shortened to 11.95 d, which is 2.56 d shorter than that in 2016, and the ROP is increased by 17.64%, presenting remarkable ROP improvement effect.