Guide apparatus

Abstract

The present invention provides a down-hole tool guide apparatus 6 suitable for use in controlling movement of a down-hole apparatus 1 provided with a pressurised working fluid supply in a borehole P. The apparatus comprises: a body 7 having a chamber 13 in which is slidably mounted a piston 14. A high pressure end 13 a of the chamber 13 is connected 36 to the pressurised working fluid supply 10 for supplying pressurised working fluid to a high pressure side 32 of said piston 14. A low pressure end 13 b of the chamber 13 is connected with the outside of the guide apparatus 6 and is provided with a spring 16 for applying a biasing force to the low pressure side 17 of the piston 14 corresponding to a predetermined threshold pressure of the pressurised fluid supply at the high pressure side of the piston 14. The body 7 mounts at least one shoe 25 having an engagement face 26. The piston 14 is operatively coupled to a shoe displacement mechanism 18, 19, 28, 29 so that the shoe 25 is held in a stowed position when the piston 14 is urged towards the high pressure end 13 a of the chamber 13 by the spring 16, and is displaced outwardly so that the engagement face 26 projects outwardly of the body 7 when the piston 14 is displaced towards the low pressure end 13 b of the chamber by supply of pressurised working fluid at a pressure higher than said threshold pressure.

What is claimed is:  
     
         1 . A down-hole tool guide apparatus suitable for use in controlling movement of a down-hole apparatus provided with a pressurised working fluid supply in a borehole, said apparatus comprising: a body having a chamber in which is slidably mounted a piston, said body being formed and arranged for connection of a high pressure end of said chamber to the pressurized working fluid supply in use of the apparatus for supplying pressurized working fluid to a high pressure side of said piston, said body being further formed and arranged for connecting a low pressure end of said chamber with the outside of said guide apparatus, said body being provided with a resilient biasing device formed and arranged for applying a biasing force to said piston corresponding to a predetermined threshold pressure of the pressurised fluid supply at the high pressure side of said piston, so as to urge said piston towards the high pressure end of the chamber, said body mounting at least one shoe, each said shoe having a radially outwardly facing longitudinally extending engagement face, said piston being operatively coupled to a shoe displacement mechanism formed and arranged so that said shoe is held in a stowed position when said piston is urged towards the high pressure end of said chamber by the resilient biasing means, and said shoe is displaced outwardly so that said engagement face projects outwardly of the body when said piston is displaced towards the low pressure end of the chamber by supply of pressurised working fluid at a pressure higher than said threshold pressure.  
     
     
         2 . An apparatus as claimed in  claim 1  wherein is provided a single said shoe, whereby said apparatus may be used as a kick-off tool.  
     
     
         3 . An apparatus as claimed in  claim 1  wherein is provided a plurality of angularly distributed said shoes, whereby said apparatus may be used as a centralising or anchoring tool.  
     
     
         4 . An apparatus as claimed in  claim 3  wherein said shoe engagement faces are provided with longitudinally extending ridges, whereby said apparatus may be used as a centralising tool.  
     
     
         5 . An apparatus as claimed in  claim 3  wherein said shoe engagement faces are provided with part annularly extending ridges, whereby said apparatus may be used as an anchoring tool.  
     
     
         6 . An apparatus as claimed in  claim 3  wherein is provided a single said piston and chamber operatively coupled to a shoe displacement mechanism for each of said shoes.  
     
     
         7 . An apparatus as claimed in  claim 1  wherein said shoe displacement mechanism comprises a camming device formed and arranged for acting between the piston and shoe(s) so as to provide a progressive radially outward displacement of said shoe(s) in response to an axial displacement of the piston.  
     
     
         8 . An apparatus as claimed in  claim 1  wherein said shoe displacement mechanism comprises a linkage having spaced apart portions pivotally connected to respective ones of the shoe(s) and the piston, said shoe(s) being captively mounted to said body so that a progressive radially outward displacement of said shoe(s) is provided in response to an axial displacement of the piston.  
     
     
         9 . An apparatus as claimed in  claim 1  wherein said chamber and piston are annular.  
     
     
         10 . An apparatus as claimed in  claim 9  wherein a conduit for said pressurised working fluid supply extends through said chamber along a central longitudinal axis thereof.  
     
     
         11 . An apparatus as claimed in  claim 1  wherein said resilient biasing device comprises a helical spring.  
     
     
         12 . An apparatus as claimed in  claim 1  wherein said resilient biasing device has a predetermined preloaded so as to require a pressurised fluid threshold pressure for initiating piston displacement, in the range from 5 to 20 bar.  
     
     
         13 . An apparatus as claimed in  claim 1  wherein said resilient biasing device has a variable spring rate.  
     
     
         14 . An apparatus as claimed in  claim 1 , wherein said chamber is connected to the interior of a pressurised fluid supply conduit, via at least one perforation in said conduit.  
     
     
         15 . An apparatus as claimed in  claim 1  wherein the pressurised fluid supply is provided, downstream of its connection to the high pressure end of said chamber, with a flow restrictive nozzle in order to increase the backpressure thereat and the pressure differential obtained for a given pressurised fluid flow rate.  
     
     
         16 . A pressurised fluid operated downhole cutting tool apparatus having a pressurised fluid—operated motor drivingly connected to a cutting tool and a pressurised fluid supply, wherein is provided a guide apparatus according to  claim 2 .  
     
     
         17 . An apparatus as claimed in  claim 16  wherein said guide apparatus is mounted between the motor and the cutting tool.  
     
     
         18 . An apparatus as claimed in  claim 16  wherein said motor is selected from a positive displacement motor and a turbine.  
     
     
         19 . A pressurised fluid operated downhole apparatus provided with an anchoring tool comprising a guide apparatus according to claim  3 .