Vertical xmas tree and workover assembly

Abstract

A vertical subsea Xmas tree ( 200 ) having a production bore ( 203 ) and two valves ( 10 ) in the production bore ( 203 ). Each valve ( 10 ) has a valve gate ( 18, 20 ) which is functionally connected to an actuator ( 38, 40 ) moving the valve gate bidirectionally between an open position and a closed position. The production bore ( 203 ) is sealed off by the valves ( 10 ) in the closed position. The valve gate ( 18, 20 ) is provided with a string cutting edge ( 34 ).

1 . A vertical subsea Xmas tree having a production bore and two valves in the production bore, wherein each valve comprises a valve gate which is functionally connected to an actuator moving the valve gate bidirectionally between an open position and a closed position, wherein the production bore is sealed off by the valves in the closed position, wherein the valve gate is provided with a string cutting edge. 
     
     
         2 . The vertical subsea Xmas tree according to  claim 1 , comprising a workover subsea control module comprising emergency disconnect package control means and vertical Xmas tree control means. 
     
     
         3 . The vertical subsea Xmas tree according to  claim 1 , comprising an annulus access bore provided with two valves, which valves are gate valves having a valve gate provided with a string cutting edge. 
     
     
         4 . A subsea workover assembly arranged above a subsea well, the subsea workover assembly comprising
 a vertical Xmas tree having a production bore provided with a production valve;   a subsea wellhead above which the vertical Xmas tree is landed;   a riser extending downwards from a surface installation;   an emergency disconnect package arranged between the riser and the vertical Xmas tree, wherein the emergency disconnect package has an emergency disconnect package through bore which is provided with an emergency disconnect package cut and seal valve; and   wherein the production valve is a cut and seal valve.   
     
     
         5 . The subsea workover assembly according to  claim 4 , wherein
 between the emergency disconnect package cut and seal valve and the production valve there exists a valve-less path.   
     
     
         6 . The subsea workover assembly according to  claim 4 , wherein the emergency disconnect package is landed directly onto the vertical Xmas tree. 
     
     
         7 . The subsea workover assembly according to  claim 4 , wherein the emergency disconnect package comprises a bore selector and that the vertical Xmas tree comprises an annulus access bore. 
     
     
         8 . The subsea workover assembly according to  claim 4 , wherein the vertical Xmas tree comprises a workover subsea control module that comprises an emergency disconnect package control means. 
     
     
         9 . A method of running a vertical Xmas tree onto a subsea wellhead, the method comprising:
 a) arranging an emergency disconnect package above a vertical Xmas tree in a vertical stack;   b) lowering the emergency disconnect package and the vertical Xmas tree into a body of water and towards a subsea wellhead, while attached to the lower end of a riser depending from a surface installation;   c) landing and locking the vertical Xmas tree to the subsea wellhead; and   wherein step a) comprises establishing a valve-less path between an emergency disconnect package cut and seal valve in an emergency disconnect package through bore and a production bore in the vertical Xmas tree.   
     
     
         10 . The method according to  claim 9 , wherein step a) comprises arranging a bore selector between the emergency disconnect package and the vertical Xmas tree. 
     
     
         11 . The method according to  claim 9 , wherein step c) comprises controlling a locking mechanism of the vertical Xmas tree via a workover subsea control module, when locking the vertical Xmas tree to the subsea wellhead.