Drag and Torque Reducing Techniques on S-Shaped Directional Wells of the Rumaila Oilfield

S-shaped directional wells in the Rumaila Oilfield are subject to large drag and torque during the drilling process and some wells experienced torques above the upper limit of rated top-drive torque. Such conditions might present significant impacts on drilling speeds, prolong required drilling time and increase drilling costs. In order to solve this problem, research was conducted on the drag and torque reducing technique in the well trajectory optimization, development and application of rotary steering system and hydraulic oscillator, drilling fluid lubricant optimization and other aspects. Accordingly, the drag and torque reducing technique was established to meet the drilling requirements of S-shaped directional wells in the Rumaila Oilfield. For this drag and torque reducing technique, S-shaped well trajectory was adopted with optimum borehole curvature of (2.85°-3.00°)/30 m and maximum hole drift angle of 30°; liquid lubricant RH3 and solid lubricant ultra-fine extruded graphite with dosage of 3% were selected; the rotary steering system was used for the directional well with horizontal displacement above 500 m or that having the construction in the Mishrif layer. At the same time, other directional wells deployed hydraulic oscillators to raise the rate of penetration and to reduce the torque. The drag and torque reducing technique was deployed in 13 S-shaped directional wells in the Rumaila Oilfield to reduce the torque by more than 30% and to raise the rate of penetration by 37.7%. It could solve the problem of large drag and torque for the S-shaped directional wells of the oilfield.