Method for Drilling Oil and Gas Wells

Abstract

When drilling or completing an oil or gas well, it is often desirable to drill a borehole at an angle to the initial borehole. A process for deflecting a well tool towards the wall of a well bore comprises positioning within the well bore a radially expandable pipe designed to curve longitudinally when its diameter is expanded, expanding the diameter of the radially expandable pipe thereby causing the pipe to curve and passing the well tool through the curved pipe: The process is particularly suitable for through-tubing operations in which a lateral bore is initiated from a production well having within the well a smaller diameter production tubing ( 14 ) comprising (i) passing through the production tube ( 14 ) a radially expandable pipe ( 1 ) designed to curve longitudinally as its diameter is expanded, into a section of well bore ( 12 ) having a diameter greater than the diameter of the production tubing ( 14 ) (ii) expanding the diameter of the radially expandable pipe ( 1 ) thereby causing the pipe to curve, (iii) passing through the curved pipe a milling device or drill bit and (iv) milling the casing or drilling into the well bore wall.

1 - 13 . (canceled) 
   
   
       14 . A process for deflecting a well tool towards the wall of a well bore comprising positioning within the well bore a radially expandable pipe designed to curve longitudinally when its diameter is expanded, expanding the diameter of the radially expandable pipe thereby causing the pipe to curve and passing the well tool through the curved pipe. 
   
   
       15 . A process as claimed in  claim 14  in which a lateral well bore is initiated from a production well having within the well bore a smaller diameter production tubing comprising (i) passing through the production tube a radially expandable pipe designed to curve longitudinally as its diameter is expanded, into a section of well bore having a diameter greater than the diameter of the production tubing, (ii) expanding the diameter of the radially expandable pipe thereby causing the pipe to curve, (iii) passing through the curved pipe a milling device or a drill bit and (iv) milling the casing or drilling into the well bore wall. 
   
   
       16 . A process as claimed in  claim 15  in which a lateral well bore is initiated from a cased production well having within the well bore a smaller diameter production tubing comprising (i) milling a window in the casing of the well bore, (ii) passing through the production tube a radially expandable pipe designed to curve longitudinally as its diameter is expanded, into a section of well bore having a diameter greater than the diameter of the production tubing, (iii) orienting the radially expandable pipe within the well bore, (iv) expanding the diameter of the radially expandable pipe thereby causing the pipe to curve into the milled window, (v) passing through the curved pipe a drill bit and (vi) drilling into the well bore wall. 
   
   
       17 . A process as claimed in  claim 14  or  claim 15  in which the radially expandable pipe is oriented within the well bore prior to expansion. 
   
   
       18 . A process as claimed in  claim 14  or  claim 15  in which at least one spacer is used to support the curved tube within the well bore. 
   
   
       19 . A process as claimed in  claim 15  in which the angle of deviation of the lateral bore is from about 0.4 to about 1.0 degree. 
   
   
       20 . A radially expandable pipe for use in the process as claimed in  claim 14  or  claim 15  which has over at least part of its length in asymmetrical wall thickness. 
   
   
       21 . A radially expandable pipe as claimed in  claim 20  in which the asymmetrical wall thickness is provided by securely fixing a length of steel longitudinally on the outer surface of a cylindrical pipe. 
   
   
       22 . A radially expandable pipe as claimed in  claim 20  in which the length of steel comprises a cylindrical section having an internal surface which is an arc of a circle having a central angle of from 2 to 20 degrees and a radius which is the same as or slightly larger than the external radius of the pipe. 
   
   
       23 . A radially expandable pipe having at least one spacer fixed to the outer surface, the spacer comprising an elongate element having a first and second end each of which is securely fixed to the pipe such that the change in length as the pipe is expanded deforms the elongate element, increasing its maximum radial distance from the centre of the pipe. 
   
   
       24 . A radially expandable pipe as claimed in  claim 23  in which the spacer is substantially cylindrical and expands substantially symmetrically. 
   
   
       25 . A radially expandable pipe as claimed in  claim 23  in which the spacer is substantially cylindrical and has elements that are designed to expand asymmetrically about the center of the pipe. 
   
   
       26 . A radially expandable pipe as claimed in  claim 23  having a plurality of spacers positioned along the length and/or around the circumference of the radially expandable pipe such that when the pipe is expanded they expand to different radial lengths to hold the curved pipe in place within the well bore.