Downhole directional drilling assembly

Abstract

The assembly comprise a bent sub ( 1411 ), and optionally a swivel ( 1480 ). The bend angle a of the bent sub in relation to the central axis of the assembly can be adjusted by rotating lower bend member ( 1431 ) relative to upper bend member ( 1430 ), which is non-rotatably attached to downhole motor ( 1460 ), using harmonic drive ( 1413 ) arranged between lower and upper bend members. In order to adjust the rotational orientation of the bent sub ( 1411 ), a swivel ( 1480 ) is provided having upper and lower swivel members ( 1432, 1433 ). Upper swivel member can be rotated relative to lower member, which is non-rotatably attached to the downhole motor, using a second harmonic drive ( 1423 ) arranged between lower and upper swivel members.

1 . A downhole tool assembly, comprising:
 a first body and a second body arranged to rotate one relative to the other about a rotation axis and   a drive arrangement between the first and the second body for rotating the first and the second body relative to each other, wherein the drive arrangement comprises a harmonic drive comprising a wave generator, a flexible gear and an outer gear, wherein one of the wave generator, flexible gear and outer gear is adapted to function as a rotary input component and another of the wave generator, flexible gear and outer gear is adapted to function as a rotary output component; and wherein the downhole tool assembly comprises at least one motor for rotating a component of the downhole tool assembly, wherein the harmonic drive is arranged in a couplable relationship with the motor so that rotation of the motor results in rotation of the first and the second bodies relative to each other.   
     
     
         2 . A downhole tool assembly as claimed in  claim 1 , wherein the remaining one of the wave generator, flexible gear and outer gear is adapted to function as a stationary component of the harmonic drive. 
     
     
         3 . A downhole tool assembly as claimed in  claim 1 , wherein the downhole tool arrangement comprises a Bottom Hole Assembly (BHA) wherein at least one of the first and second bodies is included in the BHA. 
     
     
         4 . A downhole tool assembly as claimed in  claim 3 , wherein the first and the second bodies have a common axis of rotation. 
     
     
         5 . A downhole tool assembly as claimed in  claim 4 , wherein the motor comprises a rotor component for driving the component of the downhole tool assembly and a stator component wherein the rotary input component of the harmonic drive is arranged in a couplable relationship with the motor so as to transmit rotation from the motor via the harmonic drive to the rotary output component of the harmonic drive. 
     
     
         6 . A downhole tool assembly as claimed in  claim 5 , wherein the rotary input component of the harmonic drive is arranged in a couplable relationship with the rotor component of the motor so as to transmit rotation of the rotor component of the motor via the harmonic drive to the rotary output component of the harmonic drive. 
     
     
         7 . A downhole tool assembly as claimed in  claim 5 , wherein the rotary input component of the harmonic drive is arranged in a couplable relationship with the stator component of the motor so as to permit the stator component of the motor to rotate under the influence of reactive torque acting on the stator component during rotation of the rotor component of the motor. 
     
     
         8 . A downhole tool assembly as claimed in  claim 5 , wherein a pair of harmonic drives is provided, wherein in a first harmonic drive the rotary input component is arranged in a couplable relationship with the rotor component of the motor so as to transmit rotation of the rotor component of the motor via the harmonic drive to the rotary output component of the harmonic drive, and wherein the rotary input component of the second harmonic drive is arranged in a couplable relationship with the stator component of the motor so as to permit the stator component of the motor to rotate under the influence of reactive torque acting on the stator component during rotation of the rotor component of the motor and, wherein the first harmonic drive is incorporated into the rotary output component of the second harmonic drive so that when the rotary output component of the second harmonic drive is rotated, the first harmonic drive rotates as a unit with the rotary output component of the second harmonic drive in the direction opposite to the direction of rotation of the rotary output component of the first harmonic drive, thereby enabling rotation of the rotary output component of the first harmonic drive in opposite directions. 
     
     
         9 . A downhole tool assembly as claimed in  claim 8 , wherein one of the first and second bodies comprises one of the rotor component or the stator component of the motor. 
     
     
         10 . A downhole tool assembly as claimed in  claim 9 , wherein the motor is a downhole motor for rotating a component of the downhole tool, the downhole motor being arranged in a power section of the Bottom Hole Assembly (BHA) and wherein the rotor component of the motor comprises a motor shaft extending substantially coaxially with the rotation axis of the first body relative to the second body and the stator component comprises a tubular motor housing wherein the housing encloses the motor shaft. 
     
     
         11 . A downhole tool assembly as claimed in  claim 10 , wherein the motor comprises a topmotor at surface wherein the rotor component of the motor comprises a drill pipe extending between the Bottom Hole Assembly (BHA) and the topmotor, wherein the harmonic drive is coupled to the drill pipe at the rotary input component and to the second body at the rotary output component. 
     
     
         12 . A downhole tool assembly as claimed in  claim 11 , wherein the first body comprises a drill pipe rotatable by a topmotor. 
     
     
         13 . A downhole tool assembly as claimed in  claim 12  wherein the first body comprises non-rotatable coiled tubing. 
     
     
         14 . A downhole tool assembly as claimed in  claim 13 , wherein the second body comprises a rotatable component of the BHA. 
     
     
         15 . A downhole tool assembly as claimed in  claim 14 , wherein the harmonic drive is connected between the motor shaft of downhole motor and the rotatable component of the BHA, so as to utilise the active torque of the downhole motor to rotate the rotatable component of the BHA with reduction. 
     
     
         16 . A downhole tool assembly as claimed in  claim 15 , wherein the harmonic drive is coupled to the stator component of the downhole motor and the stator component is coupled to the rotatable component of the BHA so as to utilise the reactive torque acting on the stator component to rotate the rotatable component of the BHA. 
     
     
         17 . A downhole tool assembly as claimed in  claim 14 , wherein the harmonic drive is coupled between a drill pipe and the rotatable component of the BHA, wherein rotation of the drill pipe is transmitted to the rotatable component of the BHA with reduction in order to orient a bent portion of the BHA or to allow the bent portion to rotate constantly but considerably slower than the drill pipe. 
     
     
         18 . A downhole tool assembly as claimed in  claim 17 , wherein the harmonic drive is equipped with a clutch arrangement adapted for selective interruption of the rotary connection between the drill pipe and the BHA and/or for selectively locking the harmonic drive between the drill pipe and the BHA so that the drill pipe and the BHA rotate as one piece, and/or for altering connection sequence between the motor, the wave generator, the flexible gear, the outer gear and the first or the second body of the BHA so that the first or the second body can be rotated in opposite directions. 
     
     
         19 . A downhole tool assembly as claimed in  claim 18 , wherein the harmonic drive is coupled between the motor and the first or the second body of the BHA, so that the first or the second body of the BHA is coupled with either the flexible gear or the outer gear so that the first or the second body can be rotated in the desired direction, or a clutch means is provided enabling first or the second body to be selectively coupled with either the outer gear or the flexible gear, so that the first or the second body can be rotated in opposite directions. 
     
     
         20 . A downhole tool assembly as claimed in  claim 19 , wherein the outer gear is provided in the form of a stabiliser mounted around an outer circumference of the downhole tool assembly 
     
     
         21 . A downhole tool assembly as claimed in  claim 20 , wherein the stabiliser is a non-rotating stabiliser. 
     
     
         22 . A downhole tool assembly as claimed in  claim 21 , wherein the outer gear is adapted to function as a stationary component in the harmonic drive. 
     
     
         23 . A downhole tool assembly as claimed in  claim 22 , wherein the outer gear is configured so that it remains stationary in a borehole due to friction between the outer gear and a wall of the borehole while one of the flexible gear or the wave generator functions as the rotary input component. 
     
     
         24 . A downhole tool assembly as claimed in  claim 23 , wherein the outer gear is configured so that the friction can be overcome when the outer gear is coupled to the motor to be rotated by the motor and the harmonic drive is locked to rotate as a unit together with the motor. 
     
     
         25 . A downhole tool assembly as claimed in  claim 24 , wherein the outer gear is provided with a device which is configured to prevent rotation of the outer gear in the direction opposite to the rotation of the outer gear when it is coupled to the motor and the harmonic drive is locked to rotate as a unit together with the motor, when the outer gear is required to remain stationary during the operation of the harmonic drive, and permits rotation of the outer gear when the outer gear is coupled to the motor and the harmonic drive is locked to rotate as a unit together with the motor. 
     
     
         26 . A downhole tool assembly as claimed in  claim 25 , wherein the BHA is an orienting sub in which the relative rotation between the first body and the second body results in the change of orientation of one of the two bodies with regard to the other, wherein the change in the orientation is angular, i.e. a change in the rotational angle between the first and second bodies due to relative rotation of the first and second bodies about a common axis or longitudinal, i.e. involving a change in the angle between longitudinal axes of the first and the second bodies. 
     
     
         27 . A downhole tool assembly as claimed in  claim 26 , wherein the BHA comprises a bent sub or a bent portion wherein the second body of the downhole tool assembly comprises the bent portion, wherein the bent portion has an axis positioned at an angle to a central axis of the downhole tool assembly, wherein rotation of the bent portion around the central axis of the downhole tool assembly results in a change of circumferential orientation of the bent sub. 
     
     
         28 . A downhole tool assembly as claimed in  claim 27 , wherein the bent portion or the bent sub is arranged so that the bend angle in relation to the central axis of the downhole tool assembly can be adjusted downhole, wherein the bent portion comprises first and second bend members, wherein the first bend member is co-axial with the central axis of the downhole tool assembly, and the second bend member is rotatably coupled to the first bend member and rotatable relative thereto about a second axis of rotation which is at a non-zero angle relative to the central axis whereby the relative rotation of the first and second bend members results in the change in the bend angle between the bent portion and the central axis. 
     
     
         29 . A downhole tool assembly as claimed in  claim 28 , wherein the harmonic drive comprises at least one clutch arranged so as to selectively vary the transmission of rotation between the harmonic drive and the motor, so as to disable the transmission or enable transmission of rotation with or without reduction and/or so as to change the direction of rotation at the output. 
     
     
         30 . A downhole tool assembly as claimed in  claim 29 , wherein actuating means is provided for selectively actuating the clutch. 
     
     
         31 . A downhole tool assembly as claimed in  claim 30 , wherein the clutch is adapted to selectively alternately cooperate with one or more of the wave generator, the flexible gear and the outer gear so as to enable or restrict rotation of that gear and so as to permit or restrict rotation of another gear, thereby enabling the change in the direction of rotation to occur between the first and the second body. 
     
     
         32 . A downhole tool assembly as claimed in  claim 31 , wherein the harmonic drive includes one or more additional sets of an wave generator, a flexible gear and an outer gear, wherein the additional set of gears is linked to the existing set of gears so that the transmission ratio of the harmonic drive is a product of the transmission ratios of the existing and the additional sets. 
     
     
         33 . A downhole tool assembly as claimed in  claim 32 , wherein a torque limiting device is provided at the output of the harmonic drive in order to prevent components of the downhole assembly from becoming damaged due to excessive torque. 
     
     
         34 . A downhole tool assembly as claimed in  claim 10 , wherein the harmonic drive is located above the downhole motor, but within the BHA and is connected between the drill pipe and a bent portion of the BHA so as selectively to permit the rotation of the drill pipe from surface above the harmonic drive while minimising or preventing altogether rotation of the bent portion, wherein the reduction ratio of the harmonic drive is such that the resulting rotation of the bent sub is negligibly slow compared with the rotation of the drill pipe that it can be regarded as non-existent. 
     
     
         35 . A downhole tool assembly as claimed in  claim 34 , wherein the rotatable component of the motor comprises an eccentric drive shaft of a downhole motor and the rotary input component of the harmonic drive is coupled directly to the eccentric drive shaft. 
     
     
         36 . A downhole tool assembly as claimed in  claim 35 , wherein the downhole tool assembly forms part of a drill-string or work-string. 
     
     
         37 . A directional drilling tool, comprising:
 a first end attachable to a drillstring, and a second end attachable to a drill bit;   a power section located intermediate the first and second ends, and adapted to provide power to the drill bit;   a swivel section having first and second swivel members non-rotatably attached to the first end and power section respectively, wherein the second swivel member is rotatably coupled to the first swivel member and rotatable relative thereto about a first axis of rotation which is co-axial with a longitudinal axis of the tool;   a first harmonic drive adapted to selectively rotate the second swivel member about the first axis of rotation;   an adjustable bend section having first and second bend members non-rotatably attached to the power section and the second end respectively, wherein the first bend member is co-axial with the longitudinal axis, and the second bend member is rotatably coupled to the first bend member and having a second axis positionable at a non-zero angle relative to the longitudinal axis; and   a second harmonic drive adapted to selectively rotate the first and second bend members relative each other so as to vary the angle between the longitudinal axis and the second axis.   
     
     
         38 . A directional drilling tool as claimed in  claim 37 , wherein the drilling tool comprises a measurement while drilling (MWD) tool for reading and measuring drilling parameters installed below the swivel section and above the power section. 
     
     
         39 . A directional drilling system, comprising:
 a directional drilling tool of  claim 37 ;   a drill bit attached to the second end of the tool;   a measuring device adapted to monitor the orientation and position of the drill bit;   a remote control system having an operator control interface adapted to receive manual tool control inputs; and   an electronic controller adapted to selectively activate the first and/or second harmonic drives of the tool in response to signals from the measuring device and/or remote control system.   
     
     
         40 . A directional drilling system, as claimed in  claim 39  wherein each of the swivel and adjustable bend sections comprise one or more positional sensors adapted to communicate the rotational position of the swivel and adjustable bend sections to the controller. 
     
     
         41 . A downhole tool assembly, comprising:
 a first body and a second body arranged to rotate one relative to the other about a rotation axis and   a drive arrangement between the first and the second body for rotating the first and the second body relative to each other, wherein the drive arrangement comprises a planetary gearbox comprising a sun, a planet carrier and an annulus, wherein one of the sun, planet carrier and annulus is adapted to function as a rotary input component and another of the sun, planet carrier and annulus is adapted to function as a rotary output component; and wherein the downhole tool assembly comprises a motor for rotating a component of the downhole tool assembly, wherein the planetary gearbox is arranged in a couplable relationship with the motor so that rotation of the motor results in rotation of the first and the second bodies relative to each other.   
     
     
         42 . A directional drilling tool, comprising:
 a first end attachable to a drillstring, and a second end attachable to a drill bit;   a power section located intermediate the first and second ends, and adapted to provide power to the drill bit;   a swivel section having first and second swivel members non-rotatably attached to the first end and power section respectively, wherein the second swivel member is rotatably coupled to the first swivel member and rotatable relative thereto about a first axis of rotation which is co-axial with a longitudinal axis of the tool;   a first planetary box adapted to selectively rotate the second swivel member about the first axis of rotation;   an adjustable bend section having first and second bend members non-rotatably attached to the power section and the second end respectively, wherein the first bend member is co-axial with the longitudinal axis, and the second bend member is rotatably coupled to the first bend member and having a second axis which is at a non-zero angle relative to the longitudinal axis; and   a second planetary box adapted to selectively rotate the first and second bend members relative each other so as to vary the angle between the longitudinal axis and the second axis.   
     
     
         43 . A directional drilling system, comprising:
 a directional drilling tool according to  claim 42 ;   a drill bit attached to the second end of the tool;   a measuring device adapted to monitor the orientation and position of the drill bit;   a remote control system having an operator control interface adapted to receive manual tool control inputs; and   an electronic controller adapted to selectively activate the first and/or second planetary gearboxes of the tool in response to signals from the measuring device and/or remote control system.   
     
     
         44 .- 46 . (canceled)