Abstract: Technical difficulties have been encountered in slim hole drilling in the Southern Sulige Block. The difficulties include bit selection, well trajectory control, frequent sticking during electrical logging, severe lost circulation and low penetration rate, etc. Therefore, researches on key technologies such as PDC bit optimization, PDM tool improvement, BHA optimization, well trajectory control, optimal selection of drilling fluids systems, anti-leakage and plugging were carried out, and formed key technologies for slim hole drilling in the Southern Sulige Block, which were applied in more than 80 wells. Field applications suggest that the improved PDC bit has stable performance, with high penetration rate. Among them, the drilling cycle of 6 wells is less than 10 days; the optimized BHA and PDM tools can meet the requirement of “two-run drilling” in the second-spud section. By implementing the strategy of controlling the drilling fluid density, reducing the pressure loss and pre-adding plugging material while drilling the thief zone, etc., remarkable anti-leakage and plugging effects were achieved; Drilling fluid properties have been optimized to improve the success rate of one-time electrical logging. The key drilling technologies for slim holes in the Southern Sulige Block have provided technical support for safe and efficient slim hole drilling on this area.ea.