wellbore pump of the present invention comprises a plunger having passage means which may be open or closed by a valve operated by a piston which is biased in the open position by a spring of selected strength such that the wellbore pressure may overcome the spring to close the valve when the accumulated hydrostatic pressure reaches a certain value when the valve closes the reservoir pressure forces the plunger to the surface and causes the accumulated liquids to be pumped out of the wellbore a stem extending from the top of the piston engages a top plate and causes the valve to open when the plunger reaches the top of the wellbore means is provided whereby the valve opens when it reaches the top of the wellbore and a latch may be provided to retain the plunger from returning to the bottom of the well application_number US 33492002 A description in the illustrated embodiment of fig1 a natural gas reservoir 2 is producing natural gas through perforations 4 into the wellbore 6 which is a string of hollow pipe extending to the well head at the surface above the reservoir formation is a collar 8 mounted in the wellbore at a fixed location and presenting a hollow centre with a reduced internal diameter resting on top of the collar is a plunger 10 of the elongated generally cylindrical configuration of smaller diameter than the wellbore.