Dynamic orienting reference system for directional drilling
First Claim
1. An apparatus for drilling an initial portion of a sidetracked wellbore from a well having a sidetrack opening in a casing, comprising:
- a whipstock adapted to be landed in the casing and having an inclined surface and at least one magnet positioned on the inclined surface, the whipstock adapted to be oriented to place the inclined surface facing in a desired direction;
a drill string adapted to be lowered into the casing and into engagement with the inclined surface;
a drill bit assembly on a lower end of the drill string for drilling the sidetracked wellbore through the opening; and
an instrument carried in the drill string having a magnetic sensor for detecting the magnet, the sensor having a preset alignment with the drill bit assembly, the sensor being shielded so that it will detect the magnet only when the instrument is rotated into general alignment with the magnet, the instrument providing a signal to the surface regarding orientation of the sensor relative to the magnet to enable steering of the drill bit assembly during drilling.
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Accused Products
Abstract
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.
300 Citations
21 Claims
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1. An apparatus for drilling an initial portion of a sidetracked wellbore from a well having a sidetrack opening in a casing, comprising:
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a whipstock adapted to be landed in the casing and having an inclined surface and at least one magnet positioned on the inclined surface, the whipstock adapted to be oriented to place the inclined surface facing in a desired direction;
a drill string adapted to be lowered into the casing and into engagement with the inclined surface;
a drill bit assembly on a lower end of the drill string for drilling the sidetracked wellbore through the opening; and
an instrument carried in the drill string having a magnetic sensor for detecting the magnet, the sensor having a preset alignment with the drill bit assembly, the sensor being shielded so that it will detect the magnet only when the instrument is rotated into general alignment with the magnet, the instrument providing a signal to the surface regarding orientation of the sensor relative to the magnet to enable steering of the drill bit assembly during drilling. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for guiding a drill bit assembly on a drill string while drilling an initial portion of a sidetracked wellbore from a well having a casing with a sidetrack opening therein, comprising:
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a whipstock adapted to be lowered into the casing on the drill string and set in the casing in a desired fixed orientation while the drill string is retrieved and returned with the drill bit assembly, the whipstock having an inclined surface and a plurality of magnets embedded along a centerline of the inclined surface; and
an instrument adapted to be located within the drill string, the instrument having a plurality of magnetic sensors that are shielded for detecting the magnets only when the drill string and the instrument are rotated into a general alignment with the magnets, and the instrument adapted to provide a signal to the surface regarding alignment of the sensors relative to the magnets, the sensors having a preset fixed alignment with the drill bit assembly to enable steering of the bit assembly during drilling. - View Dependent Claims (11, 12, 13, 14)
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15. A method for initiating a sidetracked wellbore from a well having a casing, comprising:
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(a) lowering a downhole assembly in the casing, the downhole assembly including a whipstock having an inclined surface and a magnet for creating a magnetic field;
(b) lowering a gyro instrument into the downhole assembly, orienting the inclined surface in a desired direction independently of the magnetic field of the magnet with the use of the gyro instrument, then setting the inclined surface in the desired direction and removing the gyro instrument;
(c) forming a sidetrack opening in the casing;
(d) lowering a drill string into the casing and engaging the inclined surface, the drill string having a steerable drill bit assembly on a lower end of the drill string, the drill string carrying a directional instrument having a magnetic sensor that has a preset fixed alignment with the drill bit assembly and is shielded so as to detect the magnetic field of the magnet only when the magnetic sensor is rotationally oriented into general alignment with the magnet;
then(e) providing signals to the surface from the magnetic sensor and rotating the directional instrument until the signals indicate that the magnetic sensor is generally aligned with the magnet, thus determining a drilling direction of the drill bit assembly;
then(f) rotating the drill bit assembly and drilling a sidetracked wellbore through the sidetrack opening. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification