The pressure-operated underbalance valve (POUV) is a production valve that is run in completions when it is necessary to pressure up on the tubing to set packers, liner hangers, etc.
The POUV can be run to perforate underbalanced in wells with existing perforations. It can also be used in horizontal or highly deviated wells where it is impractical to use the rathole pressure production valve, which requires a drop bar to operate.
The POUV is typically run between the packer and the firing head of a tubing-conveyed perforating system. This valve keeps the tubing string closed until it is time to open the valve and establish an underbalanced condition. The valve pressures up internally until the value of the shear pins is exceeded and the sleeve is pushed upward, exposing the ports.
The POUV is identical to the fill-up value (FLUP) except for the internal sleeve and thus can be converted to a FLUP by changing out the sleeve. Like the FLUP, the POUV comes in standard-pressure and high-performance (2 3/8-in only) versions and is available for H2S service by special request. It comes standard with EUE connections; other connections are available on request.