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 retractable retaining element positioned within the tubular body between another opening at the lower end and the opening at the upper end. 
     
     
         3 . The milling assembly of  claim 2 , further comprising a filter positioned within the tubular body between the retaining element and the opening at the upper end. 
     
     
         4 . The milling assembly of  claim 3 , further comprising another retractable retaining element positioned within the tubular body between the retaining element and the filter. 
     
     
         5 . 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.   
     
     
         6 . The milling assembly of  claim 4 , 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. 
     
     
         7 . The milling assembly of  claim 6 , 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. 
     
     
         8 . The milling assembly of  claim 1 , further comprising another cutting surface on the inside diameter of the lower end. 
     
     
         9 . 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. 
     
     
         10 . The milling assembly of  claim 9 , wherein the whipstock is substantially solid. 
     
     
         11 . 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.   
     
     
         12 . The milling assembly of  claim 11 , further comprising a retractable retaining element positioned within the tubular body between the other opening at the lower end and the opening at the upper end. 
     
     
         13 . The milling assembly of  claim 12 , further comprising a filter positioned within the tubular body between the retaining element and the opening at the upper end. 
     
     
         14 . The milling assembly of  claim 13 , further comprising another retractable retaining element positioned within the tubular body between the retaining element and the filter. 
     
     
         15 . The milling assembly of  claim 11 , 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.   
     
     
         16 . The milling assembly of  claim 14 , 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. 
     
     
         17 . The milling assembly of  claim 16 , 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. 
     
     
         18 . The milling assembly of  claim 11 , wherein the cutting surface extends from the inside diameter up to, but not including, the outside diameter. 
     
     
         19 . The milling assembly of  claim 18 , further comprising another cutting surface on the inside diameter of the lower end. 
     
     
         20 . The milling assembly of  claim 11 , wherein the whipstock is substantially solid. 
     
     
         21 . A method for milling an opening for a lateral wellbore in a section of casing or in a cement liner, comprising:
 lowering a milling assembly on a drilling string toward a whipstock in a wellbore partially lined with the section of casing and the cement liner;   milling the opening in the section of casing or in the cement liner when the milling assembly engages the whipstock;   circulating a fluid through the milling assembly during the milling of the opening in the section of casing or in the cement liner; and   retaining cuttings within the milling assembly when the fluid stops circulating through the milling assembly.   
     
     
         22 . The method of  claim 21 , further comprising retrieving the cuttings within the milling assembly when the milling assembly is removed from the wellbore. 
     
     
         23 . The method of  claim 21 , further comprising filtering the cuttings within the milling assembly during circulation of the fluid through the milling assembly. 
     
     
         24 . The method of  claim 21 , wherein the cuttings are retained within the milling assembly by a retaining element. 
     
     
         25 . The method of  claim 24 , wherein the retaining element is in an open position when the fluid is circulating through the milling assembly. 
     
     
         26 . The method of  claim 24 , wherein the retaining element is in a closed position when the fluid stops circulating through the milling assembly. 
     
     
         27 . The method of  claim 21 , further comprising pre-milling a portion of the section of casing to form an opening representing a pre-milled window. 
     
     
         28 . The method of  claim 21 , wherein the fluid circulating through the milling assembly enters an opening at one end of the milling assembly and exits through a side opening in the milling assembly into an annulus between the milling assembly and the section of casing or another section of casing. 
     
     
         29 . The method of  claim 28 , wherein the fluid circulating through the milling assembly enters another opening at another end of the milling assembly and exits through another side opening in the milling assembly into the annulus between the milling assembly and the section of casing or the another section of casing. 
     
     
         30 . The method of  claim 27 , further comprising positioning the whipstock within the section of casing below the pre-milled window.