Abstract: The slim hole drilling technology can effectively improve the drilling efficiency, reduce the development cost and the environmental protection pressure. In 2019, the slim hole drilling technology of Ф155.6 mm was carried out in Shenfu Block. 14 wells were applied, with an average drilling cycle of 22 days, a ROP of 7.4 m/h and a qualified rate of 72.4% for one-time cementing. There were some technical problems in the application of Ф155.6 mm slim hole in the block, such as long operation cycle, low ROP, and unable to guarantee cementing quality. Therefore, through analyzing the characteristics of the drilled formation, optimizing the well structure and trajectory, optimizing the bit, BHA and speed increasing tools, and using the improved polymer drilling fluid system, four wells were applied in similar blocks, and the drilling cycle was reduced by 36.5%. The average ROP was increased by 38.9% and the cementing qualification rate was increased to 95.9%. A relatively perfect drilling technology system suitable for Shenfu Block was gradually formed.