Improved mechanical model of the static push-the-bit rotary steerable bottom-hole assembly

Key words:  rotary steerable drilling system  static push-the-bit  bottom-hole assembly  mechanical model  continuous beam-column theory  instance analysis.

Abstract:

In this study, in order to improve the wellpath control accuracy and efficiency, the bottom-hole assembly (BHA) mechanics model, based on the structure and working principle of the static push-the-bit RSS, was rebuilt by means of the continuous beam-column theory. A new equivalent method of steerable rib was presented, in which the contact interaction between the steerable rib and the wellbore wall was taken into account, considering the steerable rib as an eccentric stabilizer with unknown eccentricity and known supporting force. Accordingly, the complementary solution condition was that the vectorial steerable force was equal to the supporting force. Theoretical and true drilling data analyses have shown that the new equivalent method of the steerable rib was more reasonable than the existing ones. The BHA static mechanical model based on the new equivalent method can increase the prediction accuracy of the wellbore parameters and meet the drilling requirements.