Abstract: Borehole instability and excessive friction were encountered during drilling the ultra-long horizontal section of horizontal wells in the shale oil reservoir in Jimusaer, Xinjiang. For safe and fast drilling of horizontal sections of 3 000–3 500 m, a friction reduction study was performed, such as optimization of the casing program, design of a dual two-dimensional trajectory, and determination of drilling parameters based on wellbore cleaning condition, etc. Moreover, an oil base drilling fluid formula with excellent performance in inhibition, stability and lubricity was identified in the laboratory. Finally, the key drilling techniques were developed for the horizontal wells with ultra-long horizontal section in the shale oil reservoir in Jimusaer, Xinjiang. The techniques were applied in three wells with a penetration rate of 10.9 m/h in the horizontal section and greatly reduced drilling time. The drifting process, electric logging and casing running in those wells were all successful in one run, without any occurrence of downhole complex situations during drilling and completion. It set the longest horizontal section record of unconventional oil and gas reservoirs in China. Research and application results show that the techniques can meet the technical requirements for safe and efficient drilling of the horizontal wells with ultra-long horizontal section in shale oil demonstration area in Jimusaer, Xinjiang and further improve the extension capacity of the horizontal section, and it is worthy of popularization and application.