Apparatus for maintaining at least bottom hole pressure of a fluid

Abstract

The apparatus includes an elongated tubular body having, in longitudinally consecutive array, a sample chamber, a pressurized gas reservoir, and an evacuate reservoir. A piston, having at least two pressure activated seals disposed in opposition, is longitudinally movable in the sample chamber. An elongated spool having a longitudinal bore and outer circumference lands and grooves, is longitudinally slidable between seated bores disposed in longitudinally opposite sides of the pressurized gas reservoir thereby providing on activation a unitary means for establishing a specific sequence of liquid and gas transfer between said chambers and reservoirs. The apparatus is prepared for use by positioning of the piston proximal to a checked influent valve, charging the distal end of the sample chamber with an incompressible fluid, charging of the pressurized gas chamber with a compressible gas, and charging of a time delay apparatus. The apparatus is then lowered in the earth bore. On expiry of the time delay the incompressible fluid is bled into the evacuate reservoir, allowing the piston to move distally and uptake work sample. Terminal piston travel begins moving the elongated spool, initiating a cascade of events in desired sequence. Initial spool movement discharges pressurized gas against a land of the spool, moving the spool forcefully to first close further liquid bleed from the sample chamber then charge the sample chamber with pressurized gas. The apparatus is then retrieved from the earth bore and work sample therein discharged directly into pressurized testing and/or pressurized storage apparatus.