Downhole weight-on-bit control for directional drilling

摘要

Directional drilling is achieved by a weight-on-bit control mechanism that is attached to a drill bit having asymmetrical cutters. A valve in the mechanism temporarily interrupts or bypasses mud flow toward the bit to correspondingly change the downward force acting thereon during a portion of each revolution. The bit will drill preferentially on that side of the bottom surface of the borehole where the downward force is increased, and thereby cause the borehole to curve in an azimuthal direction on such side.