Abstract: The drilling cost accounts for 40%-50% of the total well construction cost in unconventional oil and gas development, therefore, reducing drilling cost is very crucial to save well construction cost and improve development benefit. The optimal and fast drilling technology for middle-deep formation in Groundbirch tight gas project in Canada is introduced to provide technical reference for unconventional oil and gas horizontal well drilling in China. The specific parameters are as follows: Two sections of slim hole with horizontal section of 2200-3500 m. The first section is 222.3 mm borehole with 177.8 mm surface casing and the second section is 159.0 mm borehole with 114.3 mm production casing; The batch drilling model is applied and drilling fluid is recycled. The first section is spudded within 2hrs, and second section within 1 day; The spoon shaped well trajectory is designed by considering anti-collision, enhancing ROP, and decreasing friction drag, and the target displacement is reduced to increase the reservoir production area. The single bend screw + MWD is applied to control the well trajectory, and the Compass Software is used for anti-collision scanning. When the separation coefficient is less than 1.0, the SAG and MAG errors are corrected to ensure the safe drilling and avoid obstacles. During horizontal section drilling, the oil-based drilling fluid, high torque screw, hydro-oscillator, 52 MPa drilling pump, surface manifold and pressure control technology are adopted. Furthermore, the high rotary speed and large WOB are applied to achieve one trip completion of the horizontal sections of most horizontal wells, with the maximum daily footage of 1152 m, and ROP reaching up to 65.59 m/hr; Based on pressure distribution of wellbore and water hammer effect during fracturing, the production casing is differentially designed for different sections to save costs; From the second section, the well trajectory is designed with 8°-13° deviation section, and the floatation collar and special Tesco tool are used to running casing to greatly reduce the friction drag. The number of centralizers is increased to ensure cementing quality and greatly improve the casing running efficiency. Through the continuous optimization and improvement, the average drilling time was only 14.4 days of 14 wells drilled after Y2017 with the total well depth of 5687 m and horizontal section of 3182 m. The drilling cost per meter was decreased by 33% given that the length of horizontal section was increased by 1332 m of 158 wells drilled before 2014.