Drain Sub


The Weatherford drain sub is used to safely bleed off pressure and/or to recover samples of hydrocarbons that are trapped between ball valves in the test string—prior to breaking out the tools at the rig floor. The planned or unplanned trapping of hydrocarbons can occur within the Weatherford drill stem test string only when the downhole safety valve is run above the tester valve. The tester valve seals bi-directionally while the safety valve seals from below; hence, when the safety valve is activated and the tester valve is in the closed position, pressurized fluid can be trapped and brought to the surface.


  • Drillstem testing
  • Production testing

Features, Advantages and Benefits

  • The Drain Sub enables bleeding off pressurized hydrocarbons trapped between two ball valves inside the test string prior to breaking out the tools from the test string on the rig floor.
  • The tool enables capturing a hydrocarbon sample downhole for collection at surface.
  • The full-bore ID of the valve facilitates unrestricted flow and access for well interventions.