Patent ID: 8403060

Claim:
A subsea production tree, comprising: a tree block having a cylindrical bore; an inner wellhead assembly mounted in the tree block and having an axial passage relative to an axis of the cylindrical bore; a first plug configured to sealingly engage the axial passage at a first location; a second plug configured to sealingly engage the axial passage at a second location, the second location being spaced axially apart from the first location; wherein the axial passage, the first plug, and the second plug define a cavity, the cavity having a first volume and being adapted to retain a trapped fluid; a vent passage extending through the second plug and in fluid communication with the cavity, the vent passage being adapted to flow at least a portion of the trapped fluid from the cavity; a pressure relief member blocking the vent passage, wherein the pressure relief member is adapted to permit flow through the vent passage when the pressure in the cavity exceeds a predetermined value; and a first annular seal and a second annular seal, the first and second annular seal having the same diameter and being axially adjacent to each other, the vent passage terminating between the first and second annular seals, the first annular seal blocking downward flow in the axial passage and the second annular seal blocking upward flow in the axial passage but not downward flow, so as to allow fluid from the cavity to flow past the second annular seal.