Actual wellbore tortuosity evaluation using a new quasi-three-dimensional approach

Abstract

The irregular wellbore trajectory caused by the wellbore deviation and fluctuation makes a significant effect on the torque and drag in extending and direction drilling, especially for wellbore trajectory with obvious deviation in the drilling direction. As a consequence, a new quasi-three-dimensional wellbore tortuosity evaluation method is developed. The new method incorporates the effect of fluctuation frequency and amplitude of oscillating wellbore trajectory; a weight coefficient index that quantifies the effect of tortuosity of one segment trajectory to the entire trajectory; a ‘Peak-Valley’ principle that can decompose the irregular wellbore trajectory in various scale lengths. The studies show that the deflection angle between the segments of tortuous wellbore increases the torque and drag by strengthening the contact behaviors between the drillstring and borehole. Therefore, the deflection angle is introduced to quantify the effect of deviation in the drilling direction on wellbore tortuosity. The evaluation results of two field cases demonstrate the new method which is adapted to the wellbore trajectory fluctuating with various characteristics and can reflect the actual state of wellbore tortuosity with severe oscillation more effectively and accurately.

Keywords

• Wellbore trajectory
• Deflection angle
• Peak-valley principle
• Evaluation method