Abstract: In order to improve the drilling speed of Well QG-1 in the piedmont structural formation,the design of PDC bits was optimized.Based on careful analysis of the formation characteristics and bit data of similar layers in adjacent blocks,pertinent optimization scheme was put forward,which used modern PDC bit design methods such as force balance of cutters arrangement design,equal cutting profile,and CFD optimization of hydraulic structure,Defects of conventional PDC bit in piedmont structure such as easy abrasion,easy balling,slow drilling speed were modified.Two such designed bits altogether were used in Well QG-1,to drill from 2 075.12 m to 4 959.00 m.With a total footage of 2 883.88 m,the net drilling time of 519.2 h,the average drilling speed was 5.55 m/h,which is 58.57% faster than the expected design of 3.50 m/h,resulting in a reduction of drilling time of 30 d.Drilling in Well QG-1 showed the methods of bit selection and design optimization were feasible,at the same time precious experience for piedmont formation drilling was accumulated.