Abstract: In order to reduce operation difficulties in horizontal wells utilizing 3D wellbore trajectories and ensure safe and efficient drilling operation in the Fuling Shale Gas Field,the team proposed an optimized design method that divides the 3D wellbore trajectory into 7 sections,i.e.,"vertical section-build-up section-inclination holding section-inclination holding and correction run section-inclination holding section-build-up section-horizontal section".In this method,the first step involved establishing the trajectory design model according to horizontal projection and vertical profile of a wellbore trajectory,and later steps involved presetting the inclination holding angle and the angle-building azimuth to solve the trajectory design model.Finally,the target trajectory was optimized based on the target of least overall trajectory length.The second circular arc section of the build-up and correction run section in the conventional 3D five-section trajectory design was subdivided into inclination holding and correction run section and the build-up section on the vertical plane.To reduce difficulties in hitting the target,a conduct correction was run against the target azimuth which helped avoid simultaneous build-up and correction run operations in the extremely critical target hitting phase,.This method was applied in the wellbore trajectory design of previously drilled Well Jiaoye 14-3HF.The newly designed trajectory was compared with the originally designed trajectory and it was found that the newly designed trajectory is in closer proximity to the actual one,and the well was actually drilled with the method of firstly conducting correction run against the target and then building up the angle to hit the target in order to reduce the operation difficulties,which indicates that the 3D horizontal wellbore trajectory optimization design method is more suitable for the design and on-site operation of 3D horizontal wells drilling in the Fuling Shale Gas Field.