Coiled tubing module for riserless subsea well intervention system

Abstract

A method for riserless intervention of a subsea well includes connecting an intervention assembly to a bottom hole assembly (BHA). The BHA is connected to coiled tubing. The method further includes lowering the intervention assembly to a blowout preventer (BOP) fastened to a subsea production tree using an injector of a support vessel engaged with the coiled tubing; fastening the intervention assembly to the BOP; slacking the coiled tubing using the vessel injector; engaging a stripper of the intervention assembly with the coiled tubing; and driving the BHA through the tree and into a wellbore using a subsea injector of the intervention assembly while synchronizing both injectors to maintain the slack in the coiled tubing.

1 . A method for riserless intervention of a subsea well, comprising:
 connecting an intervention assembly to a bottom hole assembly (BHA), wherein the BHA is connected to coiled tubing;   lowering the intervention assembly to a blowout preventer (BOP) fastened to a subsea production tree using an injector of a support vessel engaged with the coiled tubing;   fastening the intervention assembly to the BOP;   slacking the coiled tubing using the vessel injector;   engaging a stripper of the intervention assembly with the coiled tubing; and   driving the BHA through the tree and into a wellbore using a subsea injector of the intervention assembly while synchronizing both injectors to maintain the slack in the coiled tubing.   
     
     
         2 . The method of  claim 1 , further comprising releasing the BHA from the intervention assembly. 
     
     
         3 . The method of  claim 1 , wherein:
 the BOP is part of a pressure control assembly (PCA), and   the BHA is disposed in a tool housing of the PCA after fastening the intervention assembly to the BOP.   
     
     
         4 . The method of  claim 3 , further comprising opening an isolation valve of the PCA before driving the BHA. 
     
     
         5 . The method of  claim 3 , further comprising washing the BHA after driving the BHA. 
     
     
         6 . The method of  claim 1 , further comprising:
 injecting fluid through the coiled tubing and into the wellbore; and   returning fluid from the wellbore to the vessel.   
     
     
         7 . The method of  claim 1 , further comprising performing an intervention operation in the wellbore using the BHA. 
     
     
         8 . The method of  claim 1 , further comprising moving the vessel a safe distance from the tree. 
     
     
         9 . A coiled tubing module for a riserless subsea intervention system, comprising:
 a stripper operable to seal against coiled tubing;   a subsea injector having:
 opposed chain loops having grippers operable to grip the coiled tubing and longitudinally move the coiled tubing; 
 outboard bearing assemblies operable to guide the chain loops; 
 a motor and sealed gear case operable to drive the chain loops, the gear case having lubricant; and 
 a pressure compensator operable to pressurize the lubricant to a pressure equal to or substantially equal to subsea pressure; and 
   a controller operable to synchronize an injector of a support vessel engaged with the coiled tubing with the subsea injector to maintain slack in the coiled tubing.   
     
     
         10 . The module of  claim 9 , further comprising a tool catcher operable to connect a bottom hole assembly connected to the coil tubing with the module. 
     
     
         11 . The module of  claim 9 , further comprising an isolation valve operable to prevent flow from a subsea wellbore through a bore of the module in a closed position. 
     
     
         12 . The module of  claim 9 , wherein the isolation valve is further operable to cut the coiled tubing or the module further comprises a coiled tubing cutter. 
     
     
         13 . The module of  claim 9 , further comprising an adapter having a connector operable by a remotely operated vehicle (ROV) for fastening the module to a pressure control assembly fastened to a subsea production tree. 
     
     
         14 . The module of  claim 13 , further comprising:
 a control relay in communication with the stripper and the motor; and   a frame fastened to the adapter and the control relay,   wherein the control relay is operable to receive a subsea jumper providing communication with the controller.   
     
     
         15 . The module of  claim 14 , further comprising a fluid sub having a port in communication with a bore of the module. 
     
     
         16 . The module of  claim 15 , further comprising a junction plate for providing fluid communication between the fluid sub and a fluid conduit extending from a support vessel.