Rotation Activated Downhole Orientation System and Method

Abstract

A rotation activated orientation system 10 for a ground drill is operated by action of magnetic fields. The system 10 incorporates a magnetically operated orientator 12 having a free state where the orientator 12 provides a substantially instantaneous indication of a position of a reference bearing of a hole being drilled by the ground drill, and a locked state where the orientator maintains the indication. The system 12 also includes a magnetic actuator 14 operatively associated with the magnetically operated orientator 12 . When the rotational speed of the ground drill is greater than a threshold speed the magnetic actuator 14 supplies a magnetic field effective to place the orientator 12 in the free state. When the rotational speed of the drill is less than the threshold speed the magnetic actuator 14 does not supply a magnetic field effective to operate the orientator so that the orientator 12 reverts to or remains in the locked state.

1 . A rotation activated orientation system for a ground drill comprising:
 a magnetically operated orientator having a free state where the orientator provides a substantially instantaneous indication of a position of a reference bearing or location in or of a hole being drilled by the ground drill, and a locked state where the orientator maintains the indication; and,   a magnetic actuator operatively associated with the magnetically operated orientator wherein when the rotational speed of the ground drill is greater than a threshold speed the magnetic actuator supplies a magnetic field effective to place the orientator in the free state, and when the rotational speed of the drill is less than the threshold speed the magnetic actuator does not supply a magnetic field effective to operate the orientator so that the orientator reverts to or remains in the locked state.   
     
     
         2 . The rotation activated orientation system according to  claim 1  comprising a time delay system arranged to delay the orientator in reverting from the free state to the locked state when the drill is rotating at a speed below the threshold speed. 
     
     
         3 . The rotation activated orientation system according to  claim 2  wherein the time delay system comprises a bleed path acting to restrict a flow rate of a fluid draining from a region which enables the orientator to move from a location corresponding to the free state to a location corresponding to the lock state. 
     
     
         4 . The rotation activated orientation system according to  claim 3  wherein the fluid is oil and the time delay system is a hydraulic time delay system which provides the time delay by restricting flow of oil through the bleed path. 
     
     
         5 . The rotation activated orientation system according to  claim 4  wherein the oil is transparent or translucent such that the indication provided by the orientator is visible through the oil. 
     
     
         6 . The rotation activated orientation system according to  claim 3  wherein the magnetic actuator comprises an electric machine or a fluid pump; and a coupling connected between the machine or the pump and the drill to impart torque to the machine or the pump when the drill rotates. 
     
     
         7 . The rotation activated orientation system according to  claim 6  wherein when the magnetic actuator is the pump, the magnetic actuator further comprises a magnet producing a magnetic field and a cavity in which the magnet is able to move between a first position where the magnet is spaced a distance from the orientator so that the magnetic field is not effective to place the orientator in the free state; and a second position where the magnet is sufficiently close to the orientator so that its magnetic field places the orientator in the free state, and wherein the pump is operable to pressurise the fluid to move the magnet from the first position to the second position. 
     
     
         8 . (canceled) 
     
     
         9 . The rotation activated orientation system according to  claim 7  wherein the magnetic actuator comprises a high pressure path providing fluid communication between an outlet of the pump and the cavity on a side of the magnet distant the orientator wherein when the drill is rotating with a speed greater than the threshold speed the pump provides pressurised fluid through the high pressure flow path to move the magnet toward the second position. 
     
     
         10 . The rotation activated orientation system according to any one of  claims 7  wherein the magnetic actuator comprises a fluid return path providing fluid communication between the cavity and an inlet of the pump. 
     
     
         11 . The rotation activated orientation system according to  claim 7  wherein the bleed path is arranged to enable a continuous circulating flow of fluid when the magnet is in the second position and while the drill is rotating at a speed greater than the threshold speed, wherein fluid flowing through the high pressure flow path and exerting pressure on the magnet holding the magnet in the second position is returned to the pump via the bleed path. 
     
     
         12 . The rotation activated orientation system according to  claim 11  comprising a sump block disposed between the pump and the magnet, the sump block defining a fluid sump and being in direct fluid communication with the bleed path, the bypass path and the fluid return path. 
     
     
         13 . The rotation activated orientation system according to  claim 12  wherein the bleed path is formed in the sump block and provides fluid communication between the fluid sump and the side of the cavity distant the orientator. 
     
     
         14 . (canceled) 
     
     
         15 . The rotation activated orientation system according to  claim 7  comprising a bias mechanism acting to bias the magnet away from the second position and toward the first position, the bias mechanism arranged so that when the drill is rotated at a speed greater than the threshold speed fluid pressure produced by the pump overcomes the bias mechanism and moves the magnet from the first position toward the second position; and when the drill is operated at a speed less than the threshold speed the bias mechanism is operable to move the magnet in a direction from the second position toward the first position. 
     
     
         16 . The rotation activated orientation system according to  claim 15  wherein the bleed path operates as a fluid brake against action of the bias mechanism to restrict a rate of action of the bias mechanism in moving the orientator towards the locked position. 
     
     
         17 . The rotation activated orientation system according to  claim 6  wherein when the magnetic actuator is an electric machine the electric machine comprises and electric generator arranged to generate an electric current when the drill is being rotated at a speed greater than the threshold speed. 
     
     
         18 . The rotation activated orientation system according to  claim 17  wherein the electric machine comprises an electro-magnet connected to the electric generator, the electro-magnet arranged to produce a magnetic field effective to place the orientator in the free state when the drill is being rotated at a speed greater than the threshold speed. 
     
     
         19 . The rotation activated orientation system according to  claim 17  wherein the orientator comprises a bias mechanism which accumulates potential energy when the orientator is being moved toward the free state by action of the magnetic actuator and converts the accumulated potential energy to kinetic energy when the drill is being rotated at a speed less than the threshold speed to return the orientator to the locked state. 
     
     
         20 . The rotation activated orientation system according to  claim 19  wherein the bleed path operates as a fluid brake against action of the bias mechanism to restrict a rate of action of the bias mechanism in moving the orientator towards the locked position. 
     
     
         21 . An orientation device comprising at least one orientation element and an associated closed loop race having a central axis in which the orientation element is confined, the race comprising first and second clamp members between which the orientation element is located the first and second clamp members being movable relative to each other between a free position where the clamp members are spaced sufficiently to enable the orientation element to roll about the axis within the closed loop race, and a locked position where the clamping members are moved toward each other to contact the orientation element, and wherein at least one of the clamping members is resiliently deformable wherein when the orientator is in the locked state, the resiliently deformable clamping members deforms about the orientation element. 
     
     
         22 . The orientation device according to  claim 21  wherein one of the clamping members comprises a resilient washer.