| 摘要 |
<p>DIFFERENTIAL VENT AND BAR ACTUATED CIRCULATING VALVE AND METHOD A tool for use downhole in a borehole for carrying out a backsurging method whereby existing open perforations are cleaned. The tool comprises an annular body having spaced cylindrical walls, each of which reciprocatingly receives spaced pistons which move individually relative to one another. A port is formed through each of the walls of each of the cylinders with the first port being normally closed by a first piston and the second port being normally open. The second piston is moved to close the second port. The tool is placed on the end of a tubing string or within a tool string and run downhole into the borehole. A packer device enables the pressure between the lower annulus, the upper annulus, and the tubing to be adjusted relative to one another. A bar is then dropped down the tubing string, contacts the second piston and moves the second piston to cover the second port. The tubing pressure is reduced to provide a pressure differential between the lower annulus and the interior of the tubing. The first valve automatically opens when a predetermined pressure differential is achieved between the tubing and lower annulus, thereby providing a predetermined pressure differential across the old perforations, and cleaning debris therefrom upon the opening of the first port.</p> |
