2 Mine used small-diameter pilot drilling,then gradually reaming the borehole and finally completed to designed size.

During theoretic research and field practice, we researched the steerable drilling horizontal section, programmed the mechanical analysis software of steerable drilling assembly with Weighted Residuals Method, and studied the rotary drilling build-angl.

This paper recounts the experiences of enhancing drill effectiveness, shorting well building period, saving cost and accurately controlling borehole trace by using guide drilling system in the production process of drilling cluster in the area of Bohai Liaodong Bay.