Method and system for drilling using gas as a drilling fluid

Abstract

A system and method of drilling. The method may generally include providing a drilling system including a rotary motor operable to rotationally drive a drill bit and providing a supply of compressible drill fluid, the supply producing an operating volumetric flow rate of fluid in a normal operating condition. The rotary motor operates at a rotational operating speed under a first volumetric flow rate of fluid, and the supply provides a volumetric flow rate of fluid greater than the first volumetric flow rate of fluid. The method further includes supplying the first volumetric flow rate of fluid from the supply to the rotary motor, and diverting a portion of fluid flow from the supply through a jet sub.

1 . A method of drilling, the method comprising:
 extending a drill string into a well bore hole, the drill string comprising a distal end arranged in the well bore;   mounting a bottom of the hole assembly at the distal end of the drill string, the bottom of the hole assembly comprising a drill bit and a rotary motor operable to rotationally drive the drill bit, the rotary motor operating at a desired operational speed in response to a threshold flow rate of compressible drill fluid;   supplying a flow of compressible drill fluid to the bottom of the hole assembly through the drill string, the flow through the drill string being at a flow rate in excess of the threshold flow rate;   providing in the drill string at least one jet sub; and   providing a bypass flow by diverting with the jet sub a portion of the flow of compressible drill fluid into the well bore surrounding the drill string, such that the diverted portion of the flow does not flow through the bottom of the hole assembly, and such that the non-diverted portion of the flow is below the threshold flow rate, the non-diverted portion of the flow operating the rotary motor to drive the drill bit.   
     
     
         2 . The method according to  claim 1 , wherein the drilling is directional, and wherein the drill string has a vertical section, a non-vertical section and a curved section connecting the vertical section and the non-vertical section, the non-vertical section defining the distal end of the drill string. 
     
     
         3 . The method according to  claim 1 , wherein the bottom of the hole assembly further comprises a hammer operable to impart percussive force on the drill bit, and wherein the non-diverted portion of the flow also operates the hammer to drive the drill bit. 
     
     
         4 . The method according to  claim 3 , wherein the hammer comprises a bypass, wherein the flow bypassing the hammer is restricted. 
     
     
         5 . The method according to  claim 1 , wherein the compressible drill fluid comprises at least one of air, nitrogen, natural gas, a mist of at least one of air, nitrogen, or natural gas, or water. 
     
     
         6 . The method according to  claim 1 , wherein a flow rate of the compressible drill fluid is varied depending upon the diameter of the bore hole, rotational speed of the air motor. 
     
     
         7 . The method according to  claim 1 , wherein a plurality of jet subs are provided in the drilling string, wherein a bypass flow through each jet sub varies. 
     
     
         8 . The method according to  claim 1 , wherein a plurality of jet subs are provided in the drilling string, wherein the bypass flow through each jet sub is equal. 
     
     
         9 . The method according to  claim 1 , wherein each jet sub comprises at least one orifice configured to direct eject flow in a direction toward a top of the bore hole, wherein a diameter of holes in the jet subs differs. 
     
     
         10 . The method according to  claim 1 , further comprising:
 removing incompressible fluid from the drilling fluid.   
     
     
         11 . A system for directional drilling, the system comprising:
 a drill string configured to extend into a well bore, the drill string comprising a distal end arranged in the well bore;   a bottom of the hole assembly mounted at the distal end of the drill string, the bottom of the hole assembly including a drill bit and a rotary motor operable to rotationally drive the drill bit, the rotary motor operating at a desired operational speed in response to a threshold flow rate of compressible drill fluid;   a supply of compressible drill fluid operable to supply compressible drill fluid to the bottom of the hole assembly through the drill string, the flow through the drill string being at a flow rate in excess of the threshold flow rate; and   at least one jet sub provided in the drill string, a portion of the flow of compressible drill fluid being diverted through the jet sub into the well bore surrounding the drill string, such that the diverted portion of the flow does not flow through the bottom of the hole assembly, and such that the non-diverted portion of the flow is below the threshold flow rate, the non-diverted portion of the flow operating the rotary motor and the hammer to drive the drill bit.   
     
     
         12 . The system according to  claim 11 , wherein the drill string comprises a vertical section, a non-vertical section and a curved section connecting the vertical section and the non-vertical section. 
     
     
         13 . The system according to  claim 11 , wherein the bottom of the hole assembly further comprises a hammer operable to impart percussive force on the drill bit. 
     
     
         14 . The system according to  claim 11 , wherein the hammer comprises a bypass, wherein the flow bypassing the hammer is restricted. 
     
     
         15 . The system according to  claim 11 , wherein the compressible drill fluid comprises at least one of air, nitrogen, natural gas, a mist of at least one of air, nitrogen, or natural gas, or water. 
     
     
         16 . The method according to  claim 11 , wherein a flow rate of the compressible drill fluid is varied depending upon the diameter of the bore hole, rotational speed of the air motor. 
     
     
         17 . The system according to  claim 11 , wherein the system comprises a plurality of jet subs provided in the drilling string, wherein a bypass flow through each jet sub varies. 
     
     
         18 . The system according to  claim 11 , wherein the system comprises a plurality of jet subs in the drilling string, wherein the bypass flow through each jet sub is equal. 
     
     
         19 . The system according to  claim 11 , wherein each jet sub comprises at least one orifice configured to direct eject flow in a direction toward a top of the bore hole, wherein a diameter of holes in the jet subs differs. 
     
     
         20 . The method according to  claim 11 , further comprising:
 an incompressible fluid removing module configured to removing incompressible fluid from the drilling fluid, wherein the incompressible fluid removing module comprises a hydro cyclone or a separator.