Dump bailer

Abstract

A dump bailer is disclosed herein comprising a tool body defining a chamber for containing a material to be deposited and an outlet in the tool body through which the material can be deposited. The dump bailer also comprises a piston assembly slideably mounted in the chamber and comprising a swabbing piston, a supply of pressurized fluid, and a valve for releasing the pressurized fluid to act on the swabbing piston to drive it along the chamber to expel material contained therein through the outlet.

1 . A dump bailer, comprising:
 a tool body defining a chamber for containing a material to be deposited;   an outlet in the tool body through which the material can be deposited; and   a piston assembly slideably mounted in the chamber and comprising a swabbing piston, a supply of pressurized fluid, and a valve for releasing the pressurized fluid to act on the swabbing piston to drive it along the chamber to expel material contained therein through the outlet.   
   
   
       2 . The dump bailer as claimed in  claim 1 , wherein the valve is operable to direct pressurized fluid to act directly on the swabbing piston. 
   
   
       3 . The dump bailer as claimed in  claim 1 , wherein the supply of pressurized fluid comprises a reservoir carried on the swabbing piston so as to be moveable therewith. 
   
   
       4 . The dump bailer as claimed in  claim 1 , further comprising an intermediate mechanism through which the pressurized fluid can act on the swabbing piston. 
   
   
       5 . The dump bailer as claimed in  claim 4 , wherein the piston assembly comprises a first stage piston slideably mounted in the tool body, and a second stage piston that is slideably mounted in the first stage piston, the second stage piston being connected to the swabbing piston, the valve operating to release pressurized fluid between the first and second stage pistons to drive the swabbing piston along the chamber. 
   
   
       6 . The dump bailer as claimed in  claim 5 , wherein a sliding seal is provided on an inner wall of the tool body, and the first stage piston comprises a head end that seals against the inner wall of the tool body, and a tail end that has a smaller diameter than the head end and seals in the sliding seal. 
   
   
       7 . The dump bailer as claimed in  claim 6 , wherein the supply of pressurized fluid comprises a reservoir defined between the head end of the first stage piston and the sliding seal on the tool body. 
   
   
       8 . The dump bailer as claimed in  claim 7 , wherein sliding movement of the first stage piston in the tool body causes the reservoir to change in volume. 
   
   
       9 . The dump bailer as claimed in  claim 6 , further comprising an opening in the tool body such that the interior of the tool body below the sliding seal is open to ambient pressure. 
   
   
       10 . The dump bailer as claimed in  claim 9 , wherein the interior of the tool body above the head end of the first stage piston is open to ambient pressure. 
   
   
       11 . The dump bailer as claimed in  claim 9 , wherein the pressurized fluid is pressurized by the effect of the ambient pressure acting on it. 
   
   
       12 . The dump bailer as claimed in  claim 9 , wherein the tool body further comprises a supplementary supply of pressurized fluid connected to the interior of the tool body above the head end of the first stage piston by means of a valve. 
   
   
       13 . The dump bailer as claimed in  claim 5 , wherein the second stage piston is mechanically connected to the swabbing piston, and the first stage piston defines a cylinder in which the second stage piston is mounted and into which the valve can release pressurized fluid to drive the second stage piston along the cylinder which in turn drives the swabbing piston along the chamber. 
   
   
       14 . The dump bailer as claimed in  claim 13 , wherein the portion of the cylinder below the second stage piston is maintained at an internal pressure that is less than the pressure of the fluid in the supply when the tool is in an ambient operating pressure environment. 
   
   
       15 . The dump bailer as claimed in  claim 1 , wherein the outlet comprises a relief valve that is normally held in a shut position until the pressure in the chamber rises above an opening pressure due to the action of the swabbing piston. 
   
   
       16 . The dump bailer as claimed in  claim 1 , wherein the outlet comprises an end fitting having an opening in a predetermined azimuthal position on the tool circumference. 
   
   
       17 . The dump bailer as claimed in  claim 1 , wherein the end fitting has a number of openings at azimuthal positions on the tool circumference. 
   
   
       18 . The dump bailer as claimed in  claim 16 , wherein the end fitting is freely rotatable. 
   
   
       19 . The dump bailer as claimed in  claim 18 , further comprising a drive mechanism to rotate the end fitting, the drive mechanism being powered by the flow of fluid from the chamber.