Patent ID: 8746350
Filing Date: 2014-06-10
Classification: E21B

Abstract:
1. A wellhead assembly, comprising: a wellhead member having an axis; a tubing hanger set in the wellhead member for supporting a string of tubing extending into the well, defining a tubing annulus below the tubing hanger; a shuttle valve assembly located within a cavity in the tubing hanger comprising: a piston selectively slidable in axial directions between a normally closed position and an open position; a flow path extending through the tubing hanger, into the tubing annulus, and through the shuttle valve assembly for flowing annulus fluid between the tubing annulus and an exterior of the tubing hanger when the piston is in the open position; an accumulator mounted below the tubing hanger in the tubing annulus, the accumulator comprising a vessel containing a pressurized fluid, the vessel being pressurized with the pressurized fluid prior to installing the tubing hanger in the wellhead member; a closing function flow line extending from the accumulator to the cavity for applying continuous closing fluid pressure to one side of the piston, continuously urging the piston to maintain shuttle valve in the normally closed position; and an open function flow passage extending through the tubing hanger from an exterior of the tubing hanger to an opposite side of the piston for selectively supplying opening fluid pressure to move the piston from the normally closed position to the open position while the accumulator continues to supply closure fluid pressure to said one side of the piston.