Downhole Tool to Be Used in a Well Beyond a Restriction

Abstract

The invention is a retrievable downhole oil tool which can travel beyond and set beneath a restriction in casing which has a larger inner diameter than that of the restriction. The tool can later unset and travel back up past the restriction to be retrieved. Design of the tool allows for a larger inner diameter than existing tools with the same outer diameter; slips which reach out further than those of existing tools, from the outer diameter of the tool to the inner diameter of the casing; and several features which prevent damage to the tool while it squeezes through a restriction.

The invention claimed is: 
     
         1 . A retrievable downhole oil tool intended to set in a well, comprising:
 (a) A slip cage and a drag spring cage that are not radially concentric with each other; and   (b) A drag spring cage which has a smaller outer diameter (not including any drag springs or blocks) than the slip cage; and   (c) A plurality of slips which each have a vertical slot in the middle; and   (d) Conical or leaf springs trapped between the slot of each slip and the underside of the slip cage.   
     
     
         2 . The tool of  claim 1 , which additionally comprises a backup ring surrounding a mandrel; which backup ring has contact with the mandrel along the backup ring's entire inner surface; and which backup ring prevents the drag spring cage from moving up along the mandrel. 
     
     
         3 . The tool of  claim 1 , which additionally comprises:
 (a) Shear pins located above or below the slip cage and drag spring cage; and   (b) A shear pin cap which protects the shear pins.   
     
     
         4 . The tool of  claim 2 , which is set by a mechanical method. 
     
     
         5 . The tool of  claim 3 , which is set by a mechanical method. 
     
     
         6 . The tool of  claim 1 , which additionally comprises
 (a) An upper cone which moves down along a threaded portion of the mandrel; and   (b) A lower cone which does not move in relation to the mandrel, and which is longer than the upper cone.   
     
     
         7 . The tool of  claim 1 , which is a tubing anchor catcher. 
     
     
         8 . The tool of  claim 2 , which is a tubing anchor catcher. 
     
     
         9 . The tool of  claim 3 , which is a tubing anchor catcher. 
     
     
         10 . The tool of  claim 4 , which is a tubing anchor catcher. 
     
     
         11 . The tool of  claim 5 , which is a tubing anchor catcher. 
     
     
         12 . The tool of  claim 6 , which is a tubing anchor catcher. 
     
     
         13 . A method of making a downhole oil tool which can travel beyond a restriction in a well with casing, which can securely set in a location beyond the restriction where the casing has a larger inner diameter than that present at the restriction, and which can later be retrieved and successfully travel past the restriction, comprising the steps of:
 (a) Choosing a mandrel with a smaller inner diameter and a smaller outer diameter than the inner diameter of the casing at the restriction;   (b) Mounting a generally tubular drag spring cage and a generally tubular slip cage on said mandrel in positions surrounding the mandrel such that the two cages are not radially concentric;   (c) Choosing a drag spring cage with a smaller outer diameter than that of the slip cage;   (d) Choosing slips with a toothed side and a smooth side opposite to the toothed side, which slips each have a slot positioned vertically on the toothed side, such that the toothed side of the slip is divided into two surfaces, while the smooth side is left intact;   (e) Choosing conical springs or leaf springs; and   (f) Installing a plurality of said slips radially in between said mandrel and said slip cage, and inserting one or more conical springs or leaf springs into the slot of each slip, such that each spring is trapped between the slot of a slip and the slip cage.   
     
     
         14 . The method of  claim 13 , additionally comprising the step of:
 (g) Installing a backup ring on a groove on said mandrel, which backup ring has contact with the mandrel along the backup ring's entire inner surface; and which backup ring prevents the drag spring cage from moving up along the mandrel.   
     
     
         15 . The method of  claim 14 , additionally comprising the steps of:
 (h) Installing a plurality of shear pins in a location on the tool which is axially below both the drag spring cage and the slip cage; and   (i) Installing a shear pin cap concentrically outside of the shear pins, thus protecting said shear pins from substances and forces in the well.