The Differential Firing Head (DFH) was designed to allow underbalanced perforating with a differential pressure-actuated firing system. The DFH works by requiring the internal pressure to be greater than the external pressure. This condition can be created when pressure is applied to the ID or when the OD pressure is reduced. The pressure required to actuate the DFH may be lower than that used for other pressure-operated firing heads because it is operated by differential pressure.
Features and Benefits
Allows underbalanced perforating in horizontal wells without a packer
Is ideal for perforating with a sucker rod or submersible pump in place
Offers added safety because it is pressure-balanced when being run into the well
Allows maximum underbalanced pressure in low-pressure wells when mechanical firing is not desirable
Can be used when equipment or well conditions will not permit the use of high pressures
Allows the use of time-delay elements as needed
The DFH is actuated after a predetermined differential pressure is created in the firing head ID. This differential pressure can be created when surface pressure is applied to the tubing or by reducing the hydrostatic pressure in the annulus.
When the predetermined differential pressure is reached, the shear pins holding the dog retainer piston will shear, allowing the dog retainer to move up. The upward movement releases the dogs holding the firing piston in place, and the internal pressure drives the firing piston into the initiator or primer.