Tubing string testing valve TST valve Drill stem testing tools
The tubing string testing (TST) valve is a full-opening valve used to pressure-test the workstring while running in the hole. The valve is operated after it is stung into a permanent packer or a retrievable
packer is set. The TST valve requires a differential pressure between the annulus and the tubing to shear. The TST valve can also be used for pip flexing if it is run below an annulus pressure-responsive circulating valve.
In downhole operation, the valve can not be closed after open.
When running in the hole, the tester valve must run in downhole in opening condition, after string testing finished, increasing annulus pressure made the flapper valve open, also can process closing well operation for tester valve(pressure-responsive valve).
The TST valve consists of:
• Flapper valve and spring.
• shear pin section
• locking dogs
TST Valve Tubing string testing valve