Abstract: A method for locating gas-lift valves in properly spaced manner within a string of production tubing extending to a production zone within a well. During calculations for valve spacing and set pressures, the spacing and reopening pressures of the valves are corrected to the lowest temperature that is expected to be encountered at any valve while lifting from the next lower valve of the gas-lift valve and piping system. An average between the flowing temperature corresponding to the rate to be produced from the next deepest valve and the geothermal temperature gradient are employed to calculate the reopening pressure of any given valve.

Abstract: A gas lift valve capable of being actuated by fluid such as a predetermined liquid head in a tubing string or by gas in a casing surrounding the tubing for introducing lifting gas from the casing into the tubing for lifting liquid in the tubing from one elevation to a higher elevation, wherein the valve has an adjustable resilient means which is adjustable for different pressure conditions from externally of the valve to thereby avoid extensive disassembly and reassembly for adjustment of the resilient means, and wherein the valve stem below the bellows is virtually eliminated whereby valve stem bowing and corkscrewing with resultant problems are overcome. The resilient means is disposed above the bellows and is isolated from well fluid so that it can operate in the absence of any fluid or pressure to thereby enable the use of various resilient materials having more desirable spring rate characteristics. Drag from the spring or resilient means is minimized and essentially eliminated.