Vent assembly

A vent assembly for use in a tubing string located downhole in a borehole comprising a housing having an axial passageway through which fluid can flow, a sub formed at each extremity of said housing for connecting the vent assembly into a tubing string;

• a vent port formed through said housing and into communication with the axial passageway;
• an elongated annular piston concentrically positioned within said housing, seal means at each extremity of said piston which sealingly engages the inner surface of said housing and the outer surface of said piston, stop means for limiting the downward travel of said piston relative to said housing, said vent port being located intermediate said seal means when said piston abuttingly engages said stop means;
• an annular sliding element concentrically arranged respective to said housing and slidably respective to said annular piston, a lateral bleed passageway formed through said housing which communicates with said axial passageway, spaced seal means on the exterior of said sliding element for sealing the outer surface of the sliding element and the inner surface of said housing, a lower stop means against which said sliding element is abuttingly received when the element is moved into a lowermost position, said lateral bleed passageway being positioned between said seals of said sliding element when the sliding element is in the lowermost position, thereby precluding flow therethrough;
• a shoulder formed on said sliding element which can be engaged by a wireline tool thereby enabling said element to be forced uphole whereupon said lateral bleed passageway is uncovered and fluid flows through said housing and into said axial passageway;
• said lower stop means includes means on said sliding element for engaging and moving said annular piston in an uphole direction so that an upward force can be applied to the piston for moving the piston uphole to thereby uncover said vent port and enable flow to occur between said axial passageway and said vent port.

Method of communicating the interior of a tubing string with a borehole annulus wherein the hydrostatic head is greater in the borehole annulus respective to the interior of the tubing, comprising the steps of:

• forming a relatively large vent port and a relatively small bleed port from the annulus into the tubing string;
• covering the vent port with a slidable annular piston, forming spaced large and small outside diameter marginal lengths on the piston and sealingly receiving the large and small outside diameter marginal lengths of the piston within complementary large and small inside diameter portions of the tubing so that the piston is forced in a downhole direction;
• covering the bleed port with a sliding element to preclude flow therethrough;
• moving the sliding element uphole by running a wireline downhole and engaging the sliding element therewith, whereupon the bleed port is uncovered and the pressure differential across the tubing is equalized;
• and,
• thereafter moving the piston uphole to uncover the vent port by engaging the piston with the sliding element and moving both the sliding element and piston uphole by further movement of the wireline.