Patent ID: 8579032

Claim:
A wellhead assembly comprising: an inner annulus in a wellbore; an outer annulus circumscribing the inner annulus; a tubular between the inner and outer annuli; a port formed in a sidewall of the tubular; and a relief valve comprising: a body mounted in the port and projecting radially outward from the tubular, a flow passage in the body having an inner radial end in communication with the inner annulus and an outer radial end radially distal from the inner radial end, a groove formed in an end of the body distal from the port and that is substantially coaxial with the port, a valve seat in the body that is biased by a spring to a closed position between the outer radial end and outer annulus, and moveable to an open position set radially inward from the closed position and spaced away from a flow path between the outer radial end and outer annulus, the valve seat further comprising an upper portion having a substantially cylindrical outer surface that selectively moves into the groove when the valve seat is in the closed position, a lower portion having a substantially cylindrical outer surface with a radius exceeding a radius of the upper portion, and a surface in pressure communication with the outer annulus, so that when the valve seat is in the closed position, the valve seat defines a flow barrier between the inner annulus and outer annulus, and when the valve seat is in the open position, the outer radius is in communication with the inner radius through the flow passage and flow path.