Flushing a tool for closed well operation and an associated method

Abstract

A closed operation subsea well tool assembly with a flushing system flushing a first fluid in the main bore ( 15 ) of the tool assembly ( 1 ). The flushing system of the tool assembly comprises a container ( 19 ) with a second fluid, a pump ( 2 ), a swab valve ( 20 ) in the top of the main bore ( 15 ), an inlet ( 3 ) in the bottom of the main bore of the tool assembly, which is connected to the pump. Outlet(s) ( 5 a, 6 a ) are below the swab valve, configured to guide out the first fluid from the main bore. A fluid channel ( 7 ) extends from the outlet ( 5 a, 6 a ) and down to channels of the wellhead module ( 10 ) or the wellhead ( 31 ). Methods using the tool assembly are also disclosed.

The invention claimed is: 
     
       1. A closed operation subsea well tool assembly for use in performing closed operations on a subsea well or on a wellhead module or a wellhead which is installed on the subsea well, the tool assembly being connectable to the wellhead module or the wellhead and comprising:
 a main bore which extends axially through the tool assembly; 
 a flushing system which is configured to flush a first fluid from the main bore, the flushing system comprising:
 a container which contains a second fluid; 
 a pump which is connected to the container; 
 at least one of an end cap and a first valve which is located at a top of the main bore, the first valve being configured to provide full mechanical access to the main bore in an open position; 
 an inlet which is connected to a bottom of the main bore, the pump being connected to the inlet; 
 at least one outlet which is connected to the top of the main bore below the at least one of the end cap and the first valve; and 
 a fluid channel having a first end which is connected to the at least one outlet and a second end which is connectable to a channel which is located in the wellhead module or in the wellhead; 
 wherein in operation of the flushing system, the pump is activated to pump the second fluid through the inlet and into the main bore to thereby displace the first fluid through the outlet and the fluid channel and into the channel located in the wellhead module or in the wellhead. 
 
 
     
     
       2. The tool assembly according to  claim 1 , wherein the tool assembly is configured to be operated on a wire from a surface vessel. 
     
     
       3. The tool assembly according to  claim 1 , wherein the second fluid is a hydrate inhibiting agent. 
     
     
       4. The tool assembly according to  claim 1 , wherein the pump is supplied with power and operated from an ROV or an electric umbilical from a surface vessel. 
     
     
       5. The tool assembly according to  claim 1 , wherein the inlet is provided with one or more valves. 
     
     
       6. The tool assembly according to  claim 1 , wherein the outlet is provided with one or more valves. 
     
     
       7. The tool assembly according to  claim 1 , wherein the fluid channel comprises a diameter which is significantly smaller than a diameter of the main bore. 
     
     
       8. The tool assembly according to  claim 1 , wherein the pump is configured for pressure testing of well barrier elements within the tool assembly or the wellhead module or the wellhead to which the tool assembly is connected. 
     
     
       9. A method of using the tool assembly of  claim 1  for installing a wellhead module on a wellhead, comprising:
 with the tool assembly, lowering a wellhead module on a wire from a drilling rig or a ship; 
 landing the wellhead module on the wellhead; 
 using the tool assembly, pulling or opening a pre-installed barrier element in the top of the wellhead to thereby enable well fluid to rise up into the main bore; 
 using the tool assembly, closing and testing valves of the wellhead module; 
 using the tool assembly, flushing the well fluid from the main bore; 
 disconnecting the tool assembly from the wellhead module and retrieving the tool assembly to the drilling rig or ship. 
 
     
     
       10. A method of using the tool assembly of  claim 1  for pulling a wellhead module which is connected to a wellhead, the method comprising:
 installing the tool on a wire from a drilling rig or a ship; 
 landing the tool assembly on the wellhead module; 
 setting a barrier element in the wellhead and pressure testing the barrier element using the pump and a fluid from the container; 
 closing the valves of the main bore of the wellhead module; 
 flushing well fluid from the main bore; 
 disconnecting the wellhead module from the wellhead and retrieving the wellhead module to the drilling rig or ship on the wire. 
 
     
     
       11. The tool assembly according to  claim 1 , wherein the container is pressure compensated.