Behind casing wash and cement

Abstract

Perf-Wash-Cement (“P/W/C”) abandonment are conducted in an offshore oil or gas well annulus, in particular the washing or cementing operation uses a rotating head with nozzles dispensing wash fluid or cement at pressure. A new design of bottom hole assembly is proposed in which the cementing tool has a relatively large diameter in order to optimize pressure whilst the wash tool has a relatively small diameter. The wash process, for a number of reasons, appears to be less sensitive to tool diameter and making the wash tool smaller reduces the overall risk of stuck pipe.

1 . A bottom hole assembly for use in a plug and abandon operation in an oil or gas well having a casing, the assembly comprising a generally cylindrical wash tool having a plurality of wash fluid nozzles and, axially connected to the wash tool, a generally cylindrical cementing tool having one or more cement nozzles, wherein the outer diameter of the wash tool is less than the outer diameter of the cementing tool, and wherein the length of the cementing tool is selected from about 25, 27.5, 30, 35, 40, 45, 47.5, 50, 55, 60 inches long and greater than 60 inches long. 
     
     
         2 . The bottom hole assembly according to  claim 1 , wherein position of the cement nozzle nearest the upper end of the cementing tool is selected from about 25, 27.5, 30, 35, 40, 45, 47.5, 50, 55, 60 inches, and greater than 60 inches from the upper end. 
     
     
         3 . The bottom hole assembly according to  claim 1 , wherein two nozzles of the cementing tool are spaced apart axially by a distance selected from at least 2, 3, 4, 5, 6, 7, and 8 inches. 
     
     
         4 . The bottom hole assembly according to  claim 1 , wherein some or all of the wash nozzles of the wash tool are angled from the axis of the tool at angle selected from about 10, 20, 30, 40, 50, 60, 70, and 80 degrees. 
     
     
         5 . The bottom hole assembly as claimed in  claim 1 , wherein some or all of the wash nozzles are angled downwardly. 
     
     
         6 . The bottom hole assembly according to  claim 1 , wherein the cementing tool is connected to the upper end of the wash tool. 
     
     
         7 . The bottom hole assembly according to  claim 1 , wherein the outer diameter of the wash tool is about 1.0 inch to 4.0 inch smaller than the drift diameter of the casing and the outer diameter of the cementing tool is about 0.25 to 1.0 inch smaller than the drift diameter of the casing. 
     
     
         8 . The bottom hole assembly according to  claim 1 , wherein the outer diameter of the wash tool is selected from about 1, 1.5, 2, 2.5, 3, 3.5 and 4 inches smaller than the drift diameter of the casing and the outer diameter of the cementing tool is selected from about 0.25, 0.5, 0.75 and 1 inch smaller than the drift diameter of the casing. 
     
     
         9 . A method of performing a plug and abandon operation in an oil or gas well having a casing, the method including passing through the casing a bottom hole assembly as claimed in  claim 1 , delivering wash fluid through apertures in the casing into a region outside the casing and delivering cement through the apertures into the region outside the casing. 
     
     
         10 . The method according to  claim 9 , wherein the assembly is moved axially downwardly whilst wash fluid is being delivered. 
     
     
         11 . The method according to  claim 9 , wherein the assembly is moved axially upwardly whilst cement is being delivered. 
     
     
         12 . A method of performing a plug and abandon operation in an oil or gas well having a casing, the method including:
 passing through the casing a bottom hole assembly of  claim 1 ;   delivering wash fluid through apertures in the casing into a region outside the casing; and   delivering cement through the apertures into the region outside the casing.   
     
     
         13 . The method according to  claim 12 , wherein position of the cement nozzle nearest the upper end of the cementing tool is selected from about 25, 27.5, 30, 35, 40, 45, 47.5, 50, 55, 60 inches, and greater than 60 inches, from the upper end. 
     
     
         14 . The method according to  claim 12 , wherein two nozzles of the cementing tool are spaced apart axially by a distance selected from at least 2, 3, 4, 5, 6, 7, and 8 inches. 
     
     
         15 . The method according to  claim 12 , wherein some or all of the wash nozzles of the wash tool are angled from the tool at angle selected from about 10, 20, 30, 40, 50, 60, 70, and 80 degrees. 
     
     
         16 . The method according to  claim 12 , wherein some or all of the wash nozzles are angled downwardly. 
     
     
         17 . The method according to  claim 12 , wherein the cementing tool is connected to the upper end of the wash tool. 
     
     
         18 . The method according to  claim 12 , wherein the outer diameter of the wash tool is between about 1.0 inch to 4.0 inch smaller than the drift diameter of the casing and the outer diameter of the cementing tool is between about 0.25 inch to 1.0 inch smaller than the drift diameter of the casing. 
     
     
         19 . The method according to  claim 12 , wherein the outer diameter of the wash tool is selected from about 1, 1.5, 2, 2.5, 3, 3.5 and 4 inches smaller than the drift diameter of the casing and the outer diameter of the cementing tool is selected from about 0.25, 0.5, 0.75 and 1 inch smaller than the drift diameter of the casing.