Downhole cleaning apparatus

Abstract

An apparatus for cleaning the area around a casing of a wellbore is described. The apparatus comprises a body configured to be located in a wellbore casing, the body defining an internal chamber for receipt of pressurised fluid. Pistons are mounted in the body and is arranged to move from an inwardly retracted condition to an outwardly deployed condition as a result of an increase in fluid pressure in the internal chamber. Pistons further comprise at least one first nozzle arranged to direct a jet of pressurised fluid from the apparatus.

1 . An apparatus for cleaning the area around a wellbore casing, the apparatus comprising:
 a body configured to be located in a casing disposed in a wellbore, the body defining an internal chamber for receipt of pressurised fluid;   at least one piston mounted to the body and being moveable from an inwardly retracted condition to the outwardly deployed condition as a result of an increase in fluid pressure in the internal chamber, such that a predetermined pressure differential between the internal chamber and the outside of the apparatus moves said at least one piston to the outwardly deployed condition; and   wherein said at least one piston further comprises an impact surface arranged to slidably engage the internal surface of a perforated casing in use and impart vibrations to said casing when the apparatus is rotated in the wellbore and the impact surface slides along said internal surface of said perforated casing.   
     
     
         2 . An apparatus according to  claim 1 , further comprising at least one nozzle arranged to direct a jet of pressurised fluid from the internal chamber out of the apparatus. 
     
     
         3 . An apparatus according to  claim 2 , wherein said at least one nozzle is formed in said piston. 
     
     
         4 . An apparatus according to  claim 1 , wherein said piston comprises an aperture through which a retaining bar projects, said retaining bar mounted to the body to retain the piston in the body. 
     
     
         5 . An apparatus according to  claim 1 , further comprising a mandrel disposed in said internal chamber, the mandrel comprising at least one port, the mandrel being moveable along the internal chamber from a position in which said at least one port is blocked to a position enabling fluid to be pumped through said at least one port to move said piston to the outwardly deployed condition. 
     
     
         6 . An apparatus according to  claim 5 , wherein the mandrel comprises a restriction adapted to receive a first ball or dart dropped through the apparatus to block fluid flow through the mandrel and enable fluid pressure to increase to move the mandrel to a position enabling fluid to be pumped through said at least one port. 
     
     
         7 . An apparatus according to  claim 6 , wherein said first ball or dart is deformable. 
     
     
         8 . An apparatus according to  claim 5 , wherein said at least one port is configured to be blocked by a second ball to enable fluid pressure to increase to force said first ball or dart through said restriction to cause retraction of said at least one piston. 
     
     
         9 . An apparatus according to any one of  claim 5 , further comprising at least one shear pin arranged to retain said mandrel in the position in which said at least one port is blocked. 
     
     
         10 . An apparatus according to  claim 1 , further comprising at least one second nozzle formed through the body. 
     
     
         11 . An apparatus according to  claim 1 , further comprising a plurality of pistons. 
     
     
         12 . An apparatus according to  claim 1 , wherein said impact surface is curved. 
     
     
         13 . A method of cleaning the area around a wellbore casing, the method comprising:
 locating an apparatus according to  claim 1  in a casing disposed in a wellbore;   increasing fluid pressure in the internal chamber to move said at least one piston to the outwardly deployed condition; and   rotating the apparatus.   
     
     
         14 . A method according to  claim 13 , wherein the step of locating the apparatus in the casing includes locating the apparatus at a position in the casing at which the casing is perforated. 
     
     
         15 . A method according to  claim 13 , wherein the step of increasing fluid pressure in the internal chamber produces a jet of fluid from said at least one nozzle. 
     
     
         16 . An apparatus for cleaning the area around a wellbore casing, the apparatus comprising:
 a body configured to be located in a casing disposed in a wellbore, the body defining an internal chamber for receipt of pressurised fluid;   at least one contact member mounted to the body and being moveable in and out of the body, wherein said at least one contact member is urged by spring means towards an outwardly deployed condition to engage the casing, said at least one contact member further comprising an impact surface arranged to slidably engage the internal surface of a perforated casing in use and impart vibrations to said casing when the apparatus is rotated in the wellbore and the impact surface slides along said internal surface of said perforated casing; and   at least one nozzle arranged to direct a jet of pressurised fluid from the internal chamber out of the apparatus.