DOWNHOLE DRILL STRING ASSEMBLY FOR WELL DIRECTIONAL DRILLING Russian patent published in 1997 - IPC

FIELD: well drilling, in particular, equipment for horizontal and vertical change of wellbore direction in directional drilling. SUBSTANCE: downhole drill string assembly includes drilling bit 1 with motor 2, whose angle of turning and plane of action relative to plane of action of drill collars are corrected by the results of determination of wellbore inclination and direction; deflecting tool installed between drilling bit and motor. Deflecting tool consists of hinged joint 4 with variable angle of misalignment and supporting-and-centering member having shaft in form of two hollow telescopically connected rods mounted for turning relative to each other and rigidly connected into one detachable unit. In this case, longitudinal axes of upper and lower connecting threads of shaft are turned relative to each other round the longitudinal axis of bushing through an angle fixed by detachable joint. Installed between lower end of shaft and downhole motor is hinged joint with variable angle of misalignment, whose plane of action coincides with plane running through longitudinal axis of bushing rotation and longitudinal axis of lower connection thread of shaft and direction of misalignment coincides with direction of drilling of wellbore. In course of lowering, the drill string assembly assumes only one position - position of stable equilibrium, at which its center lies in well axial plane and displaced to lying wall. With no circulation and starting of downhole motor 2, drill collars tend to turn back round its axis and action of reactive torque does not affect the position of deflecting tool. In case of location of drill string assembly in ellipsoid or cavernous wellbore and contact of bushing 8 with well walls, self-orientation of drill string assembly and subsequent effect of damping of reactive torque take place, i.e., orientation of deflecting tool of drill string assembly in space is preserved irrespective of the shape of cross-section of wellbore. EFFECT: provision of spatial correction of wellbore direction according to data on wellbore inclination and direction of the previous round trip due to automatic orientation of misalignment crooked drill string assembly on bottom hole before starting of drilling in the required direction and its holding in this direction during the entire round trip, and extended technological capabilities. 2 cl, 1 dwg