| 摘要 |
A directional drilling control system allows dynamic orientation of downhole drilling equipment in unstable or corrupt natural magnetic fields without the use of gyroscopic measurement devices. The system is especially suited for sidetracking wells. The system includes a permanent or retrievable whipstock having referencing magnets embedded along the centerline of its face, and a measurement while drilling (MWD) instrument assembly. The instrument assembly contains at least one sensor which can accurately determine orientation of the mud motor relative to the reference magnets. The relative positioning of the mud motor is transmitted to the surface by way of a steering tool or MWD telemetry system. The direction of the mud motor or tool face is adjusted by turning the drill pipe at the surface. As drilling progresses, shifts in the orientation of the mud motor due to reactive torque at the drill bit will be indicated in real time so that adjustments may be made at the surface as required.
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