Milling Assembly

Abstract

A milling assembly and methods for milling an opening for a lateral wellbore in a section of casing or in a cement liner.

1 . A milling assembly, comprising:
 a tubular body with an opening at an upper end and another opening at a lower end, the lower end having an inside diameter and an outside diameter; and   a cutting surface on the lower end extending from the inside diameter up to, but not including, the outside diameter.   
     
     
         2 . The milling assembly of  claim 1 , further comprising a filter positioned within the tubular body between a retaining element and the opening at the upper end. 
     
     
         3 . The milling assembly of  claim 2 , further comprising another retractable retaining element positioned within the tubular body between the retaining element and the filter. 
     
     
         4 . The milling assembly of  claim 1 , further comprising:
 a side opening in the tubular body between the opening at the upper end and the another opening at the lower end; and   another side opening in the tubular body between the side opening and another opening at the lower end or the opening at the upper end.   
     
     
         5 . The milling assembly of  claim 3 , wherein the retaining element and the other retaining element are closed and extend into an annulus of the tubular body when there is no circulation of fluid through the annulus. 
     
     
         6 . The milling assembly of  claim 5 , wherein the retaining element and the other retaining element are open and substantially parallel to an axis of the tubular body when there is circulation of fluid through the annulus. 
     
     
         7 . The milling assembly of  claim 1 , further comprising another cutting surface on the inside diameter of the lower end. 
     
     
         8 . The milling assembly of  claim 1 , further comprising a whipstock positioned to engage the cutting surface and redirect the cutting surface toward an adjacent section of casing. 
     
     
         9 . The milling assembly of  claim 8 , wherein the whipstock is substantially solid. 
     
     
         10 . A milling assembly, comprising:
 a tubular body with an opening at an upper end and another opening at a lower end, the lower end having an inside diameter and an outside diameter;   a cutting surface on the lower end; and   a whipstock positioned to engage the cutting surface and redirect the cutting surface toward an adjacent section of casing.   
     
     
         11 . The milling assembly of  claim 10 , further comprising a filter positioned within the tubular body between a retaining element and the opening at the upper end. 
     
     
         12 . The milling assembly of  claim 11 , further comprising another retractable retaining element positioned within the tubular body between the retaining element and the filter. 
     
     
         13 . The milling assembly of  claim 10 , further comprising:
 a side opening in the tubular body between the opening at the upper end and the another opening at the lower end; and   another side opening in the tubular body between the side opening and the other opening at the lower end or the opening at the upper end.   
     
     
         14 . The milling assembly of  claim 12 , wherein the retaining element and the other retaining element are closed and extend into an annulus of the tubular body when there is no circulation of fluid through the annulus. 
     
     
         15 . The milling assembly of  claim 14 , wherein the retaining element and the other retaining element are open and substantially parallel to an axis of the tubular body when there is circulation of fluid through the annulus. 
     
     
         16 . The milling assembly of  claim 10 , wherein the cutting surface extends from the inside diameter up to, but not including, the outside diameter. 
     
     
         17 . The milling assembly of  claim 16 , further comprising another cutting surface on the inside diameter of the lower end. 
     
     
         18 . The milling assembly of  claim 10 , wherein the whipstock is substantially solid.