Differential vent and bar actuated circulating valve and method

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