The tester set initial opening pressure of a gas-lift valve (GLV) and port size are no indication of its injection-gas passage at a given injection-gas pressure for unloading and/or gas lifting a well. The initial test rack opening pressure (Ptro) of a GLV creates an opening force that slightly exceeds the valve’s closing force. The importance of the required injection-gas throughput performance of a GLV for unloading and gas lifting a well increases for very high daily liquid production rate wells and for wells that the workovers are very costly.
A test procedure that allows individual injection-gas throughput rate testing of every GLV and check valve prior to being installed in a well is described in this paper. The method includes GLVs with cross-over seats that prevent stem travel probe test measurements. The test requires very little gas volume and is based on a rapid pressure decline (blow-down).
Recent computer electronics as National Instruments LabVIEW software and 4 channel data acquisition instrument control hardware can record up to 12,500 pressure readings per second per channel. Test procedures are now possible to dynamically test the gas throughput performance of a GLV in a fraction of a second.
GLV replacement can be very costly – even by wireline in wells with subsea wellheads. After setting the Ptro and aging (stabilizing) this set opening pressure, the dynamic blow-down test can be performed on each GLV with check valve. If the GLV passes this test, the valve will have the injection-gas throughput required to unload and/or gas lift the well. Every supplier of gas-lift valves should offer this testing option to the producer.