Predicting the build-up rate of single-angle & single-stabilizer turbodrill in directional well

When the existing modified three-point geometry method is used to predict the build-up rate of single-angle single-stabilizer turbodrill in a directional well, it is the geometric curvature of drilling tool that is predicted instead of the borehole curvature. What’s more, it doesn’t take full consideration of the factors influencing the build-up capacity. The upper tangential point of the downhole power drilling tool was determined by using the three-moment equation of beam-column theory, and combined with the central point of bit and the tangential point of lower stabilizer, three coordinates on the borehole axis corresponding to these three points were established. Then, a three-point geometry full-coordinate model for predicting the build-up rate of single-angle single-stabilizer turbodrill was established according to the principle of three-point geometry. Finally, the build-up rates of three kinds of turbodrills were calculated based on cases, and their variation laws with structural angle of turbodrill, stabilizer-wall clearance, eccentricity of eccentric stabilizer, and distance of stabilizer, eccentric stabilizer and angular structure from bit were comparatively analyzed. It is indicated that the stabilizer has little effect on the build-up rate of single-angle turbodrill, and in order to reduce the pipe sticking risks in deep wells, the stabilizer can be removed or be replaced with the eccentric stabilizer installed near the bit, which can improve the build-up rate of single-angle turbodrill effectively. In conclusion, this method combines the advantages of the beam-column theory and three-point geometry method and it provides convenient and effective analysis and prediction on the build-up rate of single-angle single-stabilizer turbodrill. The research results provide a reference for the prediction of the build-up rate of single-angle single-stabilizer turbodrill in ultra-deep wells.