Friction reduction and torque minimization techniques for directional wells in S-shape in Rumaila

To reduce frictional torque in S-shape directional wells in Rumaila, according to geologic conditions and difficulties in drilling operations in Rumaila, a model for calculating borehole trajectory has been built, and three speed-enhancing techniques have been tested, which shows the trajectory profile should have five segments, with the optimal borehole curvature of 2.85-3(°)/30 m and maximum deviation angle of 30°. For wells with horizontal displacement of over 500 m or directional wells in S-shape drilled in the Mishrif Formation, using rotary steering system can shorten the drilling cycle by over 3 d. As for other wells, combination of conventional directional + hydraulic oscillator is recommended, which can enhance ROP for over 35%, and shorten drilling cycle by over 1d. Three liquid lubricants and solid lubricant made of ultra-fine graphic were used in different combinations to reduce internal friction factor in open-hole from 0.52 to 0.35, whereas the friction factor in casing reduced from 0.35 to 0.28. Through comprehensive development and application of above techniques, actual torque in top drive for drilling of directional well in S-shape in Rumaila can be reduced for over 30%. With the increase of well depth and horizontal well displacement, some wells reduced by up to 150% in torques, and enhanced by 37.73% in ROP.