The control scheme for three-pad static bias device ofpush-the-bit rotary steerable system

With the increase of complex directional oil well number, domestic market demand for rotary steerable drilling technologyis rising. But in china, the control method and principle of bias unit is not clear base on static push-the-bit rotary steerable system. Soresearch on it should be necessary. The force vector resultant principle and the analysis of mathematical solution show that it is unfeasibleto control the force of each pad simultaneously by using static push-the-bit steerable tools. Due to the rotation of sleeves, the static pushthe-bit steerable tool exits can not be controlled well. The maximum usable magnitude of bias force vector is presented. According to thecontrol scheme, two pads are adopted to adjust and control the magnitude and orientation of resultant vector, and the other pad extendsto hole wall without force. At last, the control arithmetic is presented for the static push-the-bit rotary steerable tool. The block diagramcan supply theory basis for some domestic researchers who study this kind of bias unit.