MPD wellbore sealing device

A device which is made up above the BOP which creates a pressure-tight obstruction in the annulus which blocks the further passage of fluid and allows the annulus to be pressurized from the surface while drilling. When an MPD wellbore sealing device is in use, return fluids must exit the annulus through a flow spool or return flow line. ACDs and RCDs are both types of MPD wellbore sealing devices.