| CPC E21B 34/14 (2013.01) [E21B 27/02 (2013.01); E21B 29/02 (2013.01); E21B 33/1204 (2013.01); E21B 33/13 (2013.01); E21B 36/008 (2013.01)] | 25 Claims |

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1. A gas-actuated dump bailer for use in the delivery of a payload material to a downhole target region, said dump bailer comprising: an elongate payload chamber having a discharge port, via which the contents of the chamber can be deployed into said target region under the force of gravity; a sleeve that is mounted relative to the payload chamber so as to be moveable between a closed position, in which said discharge port is covered by the sleeve, and an open position, in which said discharge port is exposed by the sleeve; a sleeve actuation mechanism arranged to move the sleeve between the open and closed positions by the action of a piston which extends above or below the sleeve and that is linked, either directly or indirectly, to said sleeve, wherein said mechanism comprises a sealed chamber containing a gas-generating chemical reaction mixture; and wherein the sealed chamber has a pressure port that is configured to eject a focused stream of gas that operates the piston and moves the sleeve between the closed position and the open position.
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