Methods for Conducting a Subsea Well Intervention, and Related System, Assembly and Apparatus

Abstract

A method for conducting a subsea well intervention at a subsea well, and a related system. In particular embodiments, an assembly is provided comprising a wireline drum pressure container unit, a lubricator package having a lock chamber tube enclosing a tool string and having at least one valve in a vertical bore, and a connector used to connect the assembly to a well control package on a well head of the well. In such an embodiment, the method can include displacing well fluid in a cavity between the valve of the lubricator package and a valve of the well control package, using a clean fluid, while the valve of the lubricator package is closed. The assembly can then be disconnected from said well control package at the connector and retrieved to the surface, whereby contamination of seawater due to disconnection can be reduced or minimized.

1 . A method for conducting a subsea well intervention at a subsea well, the subsea well comprising a subsea tree with a well adapter and a well control package comprising at least one valve in a bore, the method comprising the steps of:
 (a) making up an assembly of a wireline drum pressure container unit arranged on a lubricator package with a lock chamber tube enclosing a tool string and having at least one valve in the vertical bore and a connector;   (b) lowering said assembly to said well control package and connecting the assembly using said connector to the well control package;   (c) pressure testing between said valve of the well control package and said valve of the lubricator package;   (d) opening the valve of the lubricator package and the valve of the well control package;   (e) lowering said tool string into the well;   (f) conducting a well operation using said tool string in the well;   (g) retrieving said tool string from the well back into the lock chamber tube;   (h) closing the valve of the well control package;   (i) closing the valve of the lubricator package;   (j) further pressure testing between said valve of the well control package and said valve of the lubricator package;   (k) while the valve of the lubricator package is closed, displacing well fluid in a cavity between the valve of the lubricator package and the valve of the well control package;   (l) disconnecting said assembly comprising said lubricator package and said wireline drum pressure container unit from said well control package at said connector; and   (m) retrieving the disconnected assembly to the surface.   
     
     
         2 . The method of  claim 1 , wherein the wireline drum pressure container unit comprises an enclosed traction winch. 
     
     
         3 . The method of  claim 1 , which further comprises using a clean fluid bottle for local storage of the displacement fluid in the proximity of the subsea tree and a fluid transfer system to drive the fluid from the clean fluid bottle through the cavity to one of a collector bottle, the well, or a production fluid outlet. 
     
     
         4 . The method of  claim 1 , wherein the well control package is connected to the lubricator package at surface, prior to performing steps (a) to (m). 
     
     
         5 . The method of  claim 1 , wherein either or both of the valve of the well control package, and the valve of the lubricator package, is arranged for being capable of shearing a line attached to the tool string. 
     
     
         6 . The method of  claim 1 , which further comprises, subsequently to step (k), receiving flushed-out well fluid in a collector bottle arranged on said lubricator package. 
     
     
         7 . A subsea well intervention system comprising:
 an assembly of a wireline drum pressure container package on a lubricator package on said well control package, said lubricator package for holding on a wireline a tool string in a lock chamber tube of the lubricator package, wherein the system is arranged for running said assembly to a well adapter;   a connector for connecting and disconnecting said well control package to and from said well adapter;   a first valve in said lubricator package;   a second valve in said well control package,   a connector between said first and second valves; and   a fluid transfer system arranged for displacing well fluid in a cavity between the first and second valves while the first valve is closed.   
     
     
         8 . The system of  claim 7 , further comprising a well adapter for installing on a subsea tree, the well adapter being arranged for receiving a well control package on top of the well adapter. 
     
     
         9 . The system of  claim 7 , further comprising a clean fluid bottle for local storage of non-polluting displacement fluid in proximity of the subsea tree. 
     
     
         10 . The system of  claim 7 , wherein either or both of the first and second valves is a ball valve. 
     
     
         11 . The system of  claim 7 , wherein said wireline drum pressure container package comprises, within a pressure vessel connectable on top of said lubricator package:
 a motor driven drum for said wireline and arranged for maintaining a back tension on said wireline; and   a motor driven traction winch for lowering and hoisting said line with said tool string in said lubricator and said well.   
     
     
         12 . The system of  claim 7 , wherein the well fluid is displaced using a displacement fluid (F 1 C). 
     
     
         13 . The system of  claim 12 , wherein the displacement fluid comprises seawater from a seawater inlet ( 72 ). 
     
     
         14 . The system of  claim 7 , wherein said well control package has a vertical bore and comprises a lower shear/seal valve and an isolation shear seal ball valve in the vertical bore. 
     
     
         15 . An assembly for performing a subsea well intervention at a subsea well, the assembly being configured to be releasably connected to a well head via a connector, the assembly comprising a lubricator package for containing a tool string in a chamber thereof, and being configured for displacing well fluid from a cavity between the chamber and the well head for preventing pollution of the sea upon disconnection of the assembly, the cavity being isolated from the chamber. 
     
     
         16 . Apparatus for use in performing a subsea well intervention at a subsea well, wherein an assembly is releasably connected to a well head via a connector, the assembly comprising a lubricator package for containing a tool string in a chamber thereof, the apparatus being configured to displace well fluid from a cavity between the chamber and the well head for preventing pollution of the sea upon disconnection of the assembly, the cavity being isolated from the chamber. 
     
     
         17 . (canceled)