The drop-bar-triggered surge valve (DTRV) is a tubing or rathole pressure-operated valve. It is used with tubing-conveyed perforating (TCP) to isolate the rathole from the tubing. A drop bar activates the DTRV valve by shearing a break plug inside the valve during the drop bars trip downhole to activate the firing head and detonate the perforating guns. Either tubing or rathole pressure, whichever is higher, opens the DTRV valve, applying either underbalanced or extreme overbalanced conditions to the rathole. The large flow area of the ports provides an efficient surge in either operation.
When operated in rathole-pressure mode, the DTRV valve allows an underbalanced pressure in casings with existing perforations.
When operated in tubing-pressure mode, the DTRV valve allows perforating using extreme overbalanced pressure (which may exceed the rating of the casing) by isolating the casing from the pressure before the perforating guns are detonated.
The DTRV valve can be operated in rathole-pressure mode or tubing pressure mode without modification to the valve. The operating mode can be changed at any time, even after the perforating string is in the hole.