This paper highlights the top quartile performance well delivery of Yetagun In-fill Phase 6 drilling campaign in Yetagun gas field, offshore Myanmar. Drag, Torque, Hook load and Stand Pipe Pressure that occur in an ERD well is typically higher than conventional well due to long horizontal displacement and high lateral inclination angle. Hence, the importance of planning process, execution, drilling practices and lesson learnt which essentially resulting in a successful drilling operation were discussed in the paper. PETRONAS Carigali Myanmar Limited (PCML) successfully drilled three in-fill wells: YA-01, YA-05, and YA-12ST1 which were classified as ERD based on extended reach industry experience plot with the objective to maintain the gas production rate. Excellent planning process and good teamwork among the project team members were required to tackle all the technical issues as well the environmental and logistical challenges. The unique and challenging design for YA-05 as compared to others where it has the longest tangent length which fall within 70-80° sail angle. YA-01 and YA-12ST1 were classified as ERD medium reach class design, thus require specific ERD drilling, hole cleaning, ECD monitoring, tripping and backreaming practices to ensure success of the well. The challenges in designing ERD wells were multiple such as high torque and drag, loss circulation, well collision, differential sticking, borehole instability, hole cleaning, longer open hole interval, high stand pipe pressure and high temperature. YA-12ST1 well was planned with sidetracking design utilizing whipstock and hence, tortuous wellpath which leads to high dogleg at the sidetrack point need to be considered. Losses of circulation were observed from historical development campaign of the field. Thus it was essential that extra precautions have been prepared for efficient hole cleaning and consistent penetration control. Other challenges attached with the recommended practices to overcome them including wellbore instability, differential sticking, drag and friction factors were analyzed further in this paper. In conclusion, this paper serves as a reference for future ERD well planning and execution as the overall drilling campaign achieved excellent well delivery performance in term of cost and time. This campaign has been successfully completed with remarkable achievements such as the first semi-submersible tender-assisted drilling rig used by PETRONAS group, huge total cost saving, zero lost-time injury, and successfully secured the reservoir target and meet the gas volume target. The novelty of the successful Yetagun Phase VI development wells project yielded good practices, technology used and excellent project planning that can be applied in future projects. This paper also can be a reference for future ERD well drilling in Myanmar. © 2017, Society of Petroleum Engineers.