Downhole drilling system

Abstract

A drilling system for drilling a borehole. The system comprising a drilling assembly including a drilling motor; a drill bit mounted on the drilling assembly to be rotated by the drilling motor, an axial drive mechanism connected to the drilling assembly for moving the drilling assembly through the borehole and operable to provide weight on the bit (WOB) during drilling, and a drill string connected to the drilling assembly. The drill string is a flexible conduit to convey fluid between the surface and the drilling assembly and the WOB and torque on bit (TOB) are provided downhole by the drilling assembly.

1 . A drilling system for drilling a borehole comprising:
 a drilling assembly including a drilling motor;   a drill bit mounted on the drilling assembly to be rotated by the drilling motor;   an axial drive mechanism connected to the drilling assembly for moving the drilling assembly through the borehole and operable to provide weight on the bit (WOB) during drilling; and   a drill string connected to the drilling assembly;   wherein the drill string is a flexible conduit to convey fluid between the surface and the drilling assembly and the WOB and torque on bit (TOB) are provided downhole by the drilling assembly.   
     
     
         2 . A drilling system according to  claim 1  wherein the drill string is a hydraulic conduit. 
     
     
         3 . A drilling system according to  claim 1  wherein the drill string is flexible hose constructed from polymer liners 
     
     
         4 . A drilling system according to  claim 1  wherein the drill string is service coiled tubing. 
     
     
         5 . A drilling system according to  claim 1  wherein the drilling system is electrically powered. 
     
     
         6 . A drilling system according to  claim 5  wherein the electrical power is provided by electrical cables run inside the flexible conduit. 
     
     
         7 . A drilling system according to  claim 1  wherein the drilling system is hydraulically powered. 
     
     
         8 . A drilling system according to  claim 7  further comprising a downhole alternator. 
     
     
         9 . A drilling system according to  claim 1  further comprising a control system for controlling the RPM and the WOB during drilling. 
     
     
         10 . A method of operating a drilling operations comprising:
 positioning the drilling system as claimed in  claim 1  in a borehole to be drilled;   operating the drilling motor and axial mechanism to provide WOB and torque to cause the drill bit to drill ahead; and   using the drilling string to direct fluid between the surface and the drilling assembly.