Methods and Apparatus for Wireline Drilling On Coiled Tubing

Abstract

Apparatus for drilling an underground borehole, comprising: a tubular conveyance system ( 18 ) including an electric cable and a supply of drilling fluid, the supply of drilling fluid being arranged in use to pump fluid from the surface down the inside of the tubular conveyance so as to return to the surface via the annulus between the outside of the tubular conveyance and the borehole; a drilling system comprising an electrically powered pump and a drilling motor, the pump being arranged in use to pump fluid from the borehole outside the drilling system up through the inside of the drilling system; a connector connecting the drilling system to the tubular conveyance system ( 18 ), through which the pump and motor are connected to the electric cable, and a flow diverter at which flow down the inside of the tubular conveyance system ( 18 ) is diverted into the annulus, and flow up the inside of the drilling system is diverted into the annulus.

1 . Apparatus for drilling an underground borehole, comprising:
 a tubular conveyance system including an electric cable and a supply of drilling fluid, the supply of drilling fluid being arranged in use to pump fluid from the surface down the inside of the tubular conveyance so as to return to the surface via the annulus between the outside of the tubular conveyance and the borehole;   a drilling system comprising an electrically powered drilling motor and a pump arranged in use to pump fluid from the borehole outside the drilling system up through the inside of the drilling system;   a connector connecting the drilling system to the tubular conveyance system and to the electric cable, and   a flow diverter at which flow down the inside of the tubular conveyance system is diverted into the annulus, and flow up the inside of the drilling system is diverted into the annulus.   
   
   
       2 . Apparatus as claimed in  claim 1 , wherein the drilling system has separate axial and rotary drive mechanisms. 
   
   
       3 . Apparatus as claimed in  claim 1 , wherein the axial drive mechanism comprises a crawler system. 
   
   
       4 . Apparatus as claimed in  claim 1  wherein the drilling motor comprises an electric motor powered through the electric cable. 
   
   
       5 . Apparatus as claimed in  claim 1  wherein the drilling system comprises a jet pump for pumping fluid through the drilling system. 
   
   
       6 . Apparatus as claimed in  claim 1 , wherein the tubular conveyance system comprises coiled tubing. 
   
   
       7 . Apparatus as claimed in  claim 1 , wherein the flow diverter forms part of the connector. 
   
   
       8 . Apparatus as claimed in  claim 1 , wherein the flow diverter is positioned in the tubular conveyance above the connector. 
   
   
       9 . Apparatus as claimed in  claim 1 , wherein in use, the flow diverter directs part of the drilling fluid down around the outside of the drilling system and the remainder of the fluid back to the surface around the outside of the tubular conveyance. 
   
   
       10 . Apparatus as claimed in any preceding claim, wherein the flow diverter is arranged to divert flow from the inside of the drilling system to the annulus above the point at which it diverts flow from the tubular conveyance system into the annulus. 
   
   
       11 . Apparatus as claimed in  claim 1 , further comprising a jetting system including one or more flow nozzles arranged to direct jets of fluid inside the borehole to remove accumulated deposits. 
   
   
       12 . Apparatus as claimed in  claim 1 , wherein the flow nozzles are adjustable so as to change the direction of flow of fluid therefrom. 
   
   
       13 . Apparatus as claimed in  claim 1 , wherein the flow diverter directs fluid into the flow nozzles for jetting and further comprises a valve adjustable to vary the amount of fluid directed through the flow nozzles and the amount of fluid directed into the annulus. 
   
   
       14 . Apparatus as claimed in  claim 1  further comprising a rotatable crown driven by a motor powered for use in back reaming. 
   
   
       15 . Apparatus as claimed in  claim 1 , wherein the motor is an electric motor powered by the electric cable. 
   
   
       16 . Apparatus as claimed in  claim 1 , further comprising a turbine driven by fluid flow from the tubular conveyance system and connected to drive the crown via a gear train. 
   
   
       17 . Apparatus as claimed in  claim 1 , further comprising an electric generator connected to the turbine and an electric motor connected to the crown via the gear train, the output of the generator being used to power the electric motor and drive the crown. 
   
   
       18 . A method of drilling an underground borehole using an apparatus comprising a tubular conveyance system including an electric cable and a supply of drilling fluid; a drilling system comprising an electrically powered pump and a drilling motor; a connector connecting the drilling system to the tubular conveyance system, through which the pump and motor are connected to the electric cable; and a flow diverter; the method comprising:
 pumping fluid from the surface down the inside of the tubular conveyance so as to return to the surface via the annulus between the outside of the tubular conveyance and the borehole; and   using the electrically powered pump of the drilling system to pump fluid from the borehole outside the drilling system up through the inside of the drilling system;   diverting fluid flow down the inside of the tubular conveyance system into the annulus, and diverting flow up the inside of the drilling system into the annulus using the flow diverter; and   using the drilling motor to drill the borehole using the drilling system.   
   
   
       19 . A method as claimed in  claim 18 , comprising diverting part of the drilling fluid down around the outside of the drilling system and the remainder of the fluid back to the surface around the outside of the tubular conveyance. 
   
   
       20 . A method as claimed in  claim 18 , further comprising a directing jets of fluid from one or more nozzles of a jetting system inside the borehole to remove accumulated deposits. 
   
   
       21 . A method as claimed in  claim 18  further comprising adjusting the flow nozzles so as to change the direction of flow of fluid therefrom. 
   
   
       22 . A method as claimed in  claim 18  comprising directing fluid into the flow nozzles for jetting using the flow diverter and adjusting a valve to vary the amount of fluid directed through the flow nozzles and the amount of fluid directed into the annulus. 
   
   
       23 . A method as claimed in  claim 18  further comprising back reaming the borehole using an additional electric motor in the drilling system. 
   
   
       24 . A method as claimed in  claim 18  comprising back reaming using a rotating crown driven by the drilling motor. 
   
   
       25 . A method as claimed in  claim 18 , comprising back reaming using a jetting system.