Downhole tool using a locking clutch

Abstract

A downhole tool may be operated using a locking clutch. The downhole tool may include an upper downhole motor having a rotor. The downhole tool may also include a lower downhole motor having a shaft. Both the rotor and shaft may rotate relative to the housing. The locking clutch may be coupled to the rotor and the shaft, and may transmit a torque from the rotor to the shaft. The locking clutch may include at least one locking pawl configured to move from an engaged position to a disengaged position when the shaft rotates above a disengagement speed. In the engaged position, the upper downhole motor may provide a torque boost to limit sticking or stall of a drill bit coupled to the downhole tool.

What is claimed is: 
     
         1 . A downhole tool, comprising:
 a housing having an upper end portion configured to be coupled to a drill string;   an upper downhole motor having a rotor configured to rotate relative to the housing;   a lower downhole motor having a shaft, the shaft being rotatable relative to the housing, the shaft being configured to be coupled to a bit; and   a locking clutch coupled to the rotor and the shaft, the locking clutch being configured to selectively transmit a torque from the rotor to the shaft, the locking clutch including:
 at least one locking pawl configured to engage with an inner diameter of the rotor and an outer diameter of the shaft, the at least one locking pawl being biased into an engaged position, and the at least one locking pawl being configured to be in a disengaged position when the shaft rotates above a disengagement speed and in an engaged position when the shaft rotates below the disengagement speed. 
   
     
     
         2 . The downhole tool of  claim 1 , the locking clutch being configured to use the at least one locking pawl to selectively transmit the torque from the rotor to the shaft when the at least one locking pawl is in the engaged position. 
     
     
         3 . The downhole tool of  claim 1 , the at least one locking pawl being biased into the engaged position when the shaft rotates below the disengagement speed. 
     
     
         4 . The downhole tool of  claim 1 , the at least one locking pawl being configured to be biased into the disengaged position by a centrifugal force when the shaft is rotated above the disengagement speed. 
     
     
         5 . The downhole tool of  claim 1 , the inner diameter of the rotor including a plurality of locking notches configured to receive a trailing end of the at least one locking pawl when the at least one locking pawl is in the engaged position. 
     
     
         6 . The downhole tool of  claim 1 , the outer diameter of the shaft including a plurality of recesses configured to receive a leading end of the at least one locking pawl when the at least one locking pawl is in the engaged position. 
     
     
         7 . The downhole tool of  claim 1 , the at least one locking pawl being biased into the engaged position by one or more biasing mechanisms positioned between the at least one locking pawl and a carrier assembly coupled to the outer diameter of the shaft. 
     
     
         8 . The downhole tool of  claim 1 , the at least one locking pawl being configured to rotate from the engaged position to the disengaged position about at least one pivot axis. 
     
     
         9 . The downhole tool of  claim 1 , the upper downhole motor being configured to have runaway rotational speed that is lower than a runaway rotational speed of the lower downhole motor. 
     
     
         10 . The downhole tool of  claim 1 , the locking clutch being configured to selectively transmit the torque from the rotor to the shaft to prevent a stall condition of the shaft. 
     
     
         11 . The downhole tool of  claim 1 , the disengagement speed being equal to a runaway rotational speed of the upper downhole motor. 
     
     
         12 . The downhole tool of  claim 1 , the upper downhole motor including a positive displacement motor, and the rotor including a rotor subassembly. 
     
     
         13 . The downhole tool of  claim 1 , the lower downhole motor including a turbodrill. 
     
     
         14 . A drilling tool, comprising:
 a housing;   a positive displacement motor coupled to the housing, the positive displacement motor including a rotor configured to rotate relative to the housing;   a turbodrill having a shaft that is rotatable relative to the housing;   a locking clutch between the positive displacement motor and the turbodrill, the locking clutch being configured to selectively transmit a torque from the rotor to the shaft, the locking clutch including at least one locking pawl configured to engage the rotor and the shaft when in an engaged position, and to disengage at least one of the rotor or the shaft when in a disengaged position as a result of the shaft rotating at or above a disengagement speed; and   a drill bit coupled to the shaft of the turbodrill.   
     
     
         15 . The drilling tool of  claim 15 , the locking clutch being configured to selectively transmit the torque from the rotor to the shaft when the at least one locking pawl is in the engaged position. 
     
     
         16 . The drilling tool of  claim 15 , the at least one locking pawl being biased by one or more biasing mechanisms into the engaged position when the shaft rotates below the disengagement speed, and biased by a centrifugal force into the disengaged position when the shaft rotates above the disengagement speed. 
     
     
         17 . The drilling tool of  claim 15 , an inner diameter of the rotor including a plurality of locking notches configured to receive a trailing end of the at least one locking pawl when the at least one locking pawl is in the engaged position, and an outer diameter of the shaft including a plurality of recesses configured to receive the at least one locking pawl in the engaged position. 
     
     
         18 . A method, comprising:
 tripping a downhole tool into a wellbore, the downhole tool including an upper downhole motor, a lower downhole motor, and a clutch coupled to, and positioned between, the upper and lower downhole motors, the clutch being configured to selectively transmit torque from the upper downhole motor to the lower downhole motor;   rotating a shaft of the lower downhole motor above a threshold speed and, in response, not transmitting torque of the upper downhole motor to the lower downhole motor; and   rotating the shaft below the threshold speed and, in response, using the clutch to transmit torque from the upper downhole motor to the lower downhole motor.   
     
     
         19 . The method of  claim 18 , wherein:
 the upper downhole motor has a rotor;   the lower downhole motor has a rotatable shaft; and   the clutch is a locking clutch and includes at least one locking pawl that is rotatable between an engaged position in which the locking clutch transmits torque between the rotor and the shaft and a disengaged position in which the locking clutch does not transmit torque between the rotor and the shaft.   
     
     
         20 . The method of  claim 19 , wherein the threshold speed is a disengagement speed and the locking pawl has at least two axes of rotation, and wherein:
 rotating the shaft above the disengagement speed causes the at least one locking pawl to be in the disengaged position; and   rotating the shaft below the disengagement speed causes the at least one locking pawl to move to the engaged position and to transmit the torque from the rotor to the shaft.