Abstract: In order to ensure the safe and smooth drilling of Well Yuanping 1,the first horizontal well with long lateral section,the drilling engineering design of the well was studied.In view of the tricky issues associated with long lateral section such as buckling of drill string,big drag/torque,difficult borehole cleaning and casing running,etc,Landmark software was used to calculate drag/torque and drill string buckling at different design profiles,different target distances and borehole curvatures,and the borehole trajectory was designed based on the simulation results,BHA of the horizontal section on the third spud was optimized based on the drill string buckling in sliding drilling and rotary drilling simulated by Landmark software,and drilling parameters of the horizontal section was optimized based on the simulated effect of drilling parameters on cuttings bed thickness.The simulation results show that running casing with floating sub can reduce friction and buckling,so the technique was adopted in running casing in this well.There were no complexities or accidents in drilling,completion,wireline logging and casing running,indicating that the engineering design is proper,and the technical difficulties in drilling long horizontal section can be overcome.