Patent ID: 7445049

Claim:
A gas operated pump for lifting fluid from a wellbore to a surface of the earth, comprising: a tubular chamber disposed in the wellbore for accumulating the fluid, a production tubular for delivering the fluid from the chamber to the surface; a first check valve for allowing fluid flow from the wellbore to the chamber; a second check valve for allowing fluid flow from the chamber to the production tubular; a gas tubular for delivering compressed gas from the surface to the chamber; a vent tubular for relieving the gas from the chamber to the surface; and a valve assembly located at the surface and comprising: a housing having a longitudinal bore therethrough; a first port formed through the housing and in fluid communication with a gas supply; a second port formed through the housing and in fluid communication with the gas tubular; a third port formed through the housing and in fluid communication with a vent line; and a fourth port formed through the housing and in fluid communication with the vent tubular; and a valve disposed in the housing and operable to alternately provide fluid communication between the first and second ports and the third and fourth ports.