System including a barrier arrangement in a wellhead assembly

A system comprising a tubing hanger 104 positioned in or below a wellhead housing 102 coupled to a subsea well. A tree cap 108 is fluidly coupled to the tubing hanger and disposed atop the wellhead housing. A pair of master production valves 118A are configured to be selectively actuated from an open position to a closed position to shut in the subsea well. Each of the pair of master production valves are located within or below the wellhead housing. A method comprising the system is also described. Preferably, the system comprises a wellhead sensor and injector module (504, Fig 5) configured to provide access for sensing and/or chemical injection into the well. A second invention relates to a system comprising: a tubing hanger configured to be positioned in a wellhead housing; a tree cap configured to be fluidly coupled to the tubing hanger and a valve module (502, Fig 5) configured to be fluidly coupled between the tubing hanger and the tree cap. The valve module comprises a pair of master production valves.