Abstract: A pressure-actuated valve fit to a tubing string for alternately closing to communicate fluids from a wellbore to the tubing string and opening to communicate fluids from a wellbore annulus to the tubing string. The valve is particularly useful for lifting liquids which accumulate in the tubing string when the reservoir has a diminished pressure. In this case, gas is accumulated in the wellbore annulus and when the valve is opened the gas enters the valve and is directed to the tubing string for lifting the liquids. The valve is closed by a spring and has a closing-assist which applies an additional force to the spring to ensure the valve is fully closed.

Abstract: A pressure-actuated valve fit to a tubing string for alternately closing to communicate fluids from a wellbore to the tubing string and opening to communicate fluids from a wellbore annulus to the tubing string. The valve is particularly useful for lifting liquids which accumulate in the tubing string when the reservoir has a diminished pressure. In this case, gas is accumulated in the wellbore annulus and when the valve is opened the gas enters the valve and is directed to the tubing string for lifting the liquids. The valve is closed by a spring and has a closing-assist which applies an additional force to the spring to ensure the valve is fully closed.

Abstract: A differential pressure valve has a valve body containing a main piston axially moveable therein to open a fluid inlet to a fluid outlet at preset high pressure and to close at a preset lower pressure. A high pressure trigger piston and a low pressure trigger piston are operable in the main piston to alternately engage and lock the main piston to the valve body in one of the closed and open positions. A ball shifts in a port in the main piston to alternately straddle between at least one annular locking groove in the valve body and a release recess in a respective trigger piston. The ball can shift to alternately reside to straddle the valve body and main piston in the locked position or to straddle the main piston and trigger piston in the unlocked position. The trigger pistons and main pistons are mechanically biased to urge the pistons against the fluid pressure at the inlet.