Actively Controlled Rotary Steerable Drilling System (RSS)

Abstract

Aspects of the disclosure can relate to a system that includes an input shaft to be driven at a nominal uncontrolled rotational speed, and an output shaft coupled with the input shaft to drive a rotary mechanism. The prime mover can be a mud turbine or a motor, and the input shaft can be driven by, for example, drilling fluid. The system also includes a drive mechanism mechanically coupling the input shaft to the output shaft to drive the rotary mechanism at a controlled rotational speed. The system further includes a secondary input mechanically coupled with the drive mechanism, where the secondary input is driven as a control input to drive the rotary mechanism at the controlled rotational speed. The drive mechanism can be a continuously variable transmission and/or a constant speed drive, and the secondary input can be a servo motor.

What is claimed is: 
     
         1 . A down hole drill assembly comprising:
 an input shaft coupled with a prime mover to be driven at a nominal uncontrolled rotational speed;   an output shaft coupled with the input shaft to drive a rotary mechanism;   a drive mechanism mechanically coupling the input shaft to the output shaft to drive the rotary mechanism at a controlled rotational speed; and   a secondary input mechanically coupled with the drive mechanism, the secondary input to be driven as a control input to drive the rotary mechanism at the controlled rotational speed.   
     
     
         2 . The down hole drill assembly as recited in  claim 1 , wherein the prime mover comprises at least one of a mud turbine or a motor. 
     
     
         3 . The down hole drill assembly as recited in  claim 1 , wherein the rotary mechanism comprises a rotary valve of a rotary steerable drilling system. 
     
     
         4 . The down hole drill assembly as recited in  claim 1 , wherein the drive mechanism comprises at least one of a continuously variable transmission or a constant speed drive. 
     
     
         5 . The down hole drill assembly as recited in  claim 1 , wherein the drive mechanism comprises a continuously variable transmission and a constant speed drive. 
     
     
         6 . The down hole drill assembly as recited in  claim 1 , wherein the secondary input comprises a servo motor. 
     
     
         7 . A method comprising:
 driving an input shaft coupled with a prime mover at a nominal uncontrolled rotational speed;   driving a rotary mechanism with an output shaft coupled with the input shaft;   mechanically coupling the input shaft to the output shaft with a drive mechanism to drive the rotary mechanism at a controlled rotational speed;   mechanically coupling a secondary input with the drive mechanism; and   driving the secondary input as a control input to drive the rotary mechanism at the controlled rotational speed.   
     
     
         8 . The method as recited in  claim 7 , wherein the prime mover comprises at least one of a mud turbine or a motor. 
     
     
         9 . The method as recited in  claim 7 , wherein the rotary mechanism comprises a rotary valve of a rotary steerable drilling system. 
     
     
         10 . The method as recited in  claim 7 , wherein the drive mechanism comprises at least one of a continuously variable transmission or a constant speed drive. 
     
     
         11 . The method as recited in  claim 7 , wherein the drive mechanism comprises a continuously variable transmission and a constant speed drive. 
     
     
         12 . The method as recited in  claim 7 , wherein the secondary input comprises a servo motor. 
     
     
         13 . A system comprising:
 an input shaft to be driven at a nominal uncontrolled rotational speed by fluid flow;   an output shaft coupled with the input shaft to drive a rotary mechanism;   a drive mechanism mechanically coupling the input shaft to the output shaft to drive the rotary mechanism at a controlled rotational speed; and   a secondary input mechanically coupled with the drive mechanism, the secondary input to be driven as a control input to drive the rotary mechanism at the controlled rotational speed.   
     
     
         14 . The system as recited in  claim 13 , wherein the fluid flow comprises drilling fluid flow. 
     
     
         15 . The system as recited in  claim 13 , wherein the input shaft is coupled with a prime mover. 
     
     
         16 . The system as recited in  claim 15 , wherein the prime mover comprises a mud turbine. 
     
     
         17 . The system as recited in  claim 13 , wherein the rotary mechanism comprises a rotary valve of a rotary steerable drilling system. 
     
     
         18 . The system as recited in  claim 13 , wherein the drive mechanism comprises at least one of a continuously variable transmission or a constant speed drive. 
     
     
         19 . The system as recited in  claim 13 , wherein the drive mechanism comprises a continuously variable transmission and a constant speed drive. 
     
     
         20 . The system as recited in  claim 13 , wherein the secondary input comprises a servo motor.