Purpose
The Underbalancing Pressure Sub is used in a perforating system to provide an economical method of achieving an underbalanced condition between the tubing and wellbore formation. The tool incorporates a high strength ceramic dome which prevents communication between tubing and tubing / casing annulus until a detonating bar is dropped from surface. This tool can be used in other applications where the operator requires the formation to be surged after or during a stimulation. This tool should not be used for snubbing operations.

Operation
The non-ported underbancing pressure sub is installed in the tubing string normally above a packer to create the desired underbalanced condition. This tool prevents fluid from entering the tubing string above the packer, tubing maybe run completely dry or partly filled. When the operator is ready to detonate and fire the perforating the guns, a drop bar is released into the tubing from surface thus passing through the tool which shatters the ceramic dome, the drop bar continues on down the tubing string to fire the perforating gun(s) exposing the wellbore to this underbalanced condition.

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