The Drain Valve (also known as a Bleed-off Valve) is used to drain fluid from the tubing string before starting well intervention or workover operations on ESP-equipped wells.
It is installed above the check valve to prevent wet pulling during tubing retrieval. Additionally, the valve allows for well killing operations through the tubing.
Before starting the operation, the workover crew drops a shear bar (or drop bar) down the tubing string. The shear bar must have a valid certificate, which is kept by the wellsite supervisor or their designated representative.
If the fluid level in the tubing is deep below the wellhead, the crew must either pull the tubing string with the ESP until the fluid is visually present or top up the tubing with fluid. This procedure is performed to reduce the shear bar's falling velocity and prevent damage to the ESP components (such as the check valve or the fishing head).
The drain valve features a brass shear plug with a rubber O-ring seal. The plug is a consumable part and must be replaced after being sheared by the drop bar.
The drain valve is typically installed one joint above the check valve, while the check valve is usually installed on the second joint above the ESP fishing head.