COMPLETING THE WELL
1.9 Installing the tubing string and tubing hanger
The tubing string is made up and run in hole. The tubing hanger is attached to the top of the string and the entire assembly is run through the drilling riser and BOP, on either a completion riser or drillpipe, and landed in the wellhead. If an oriented tubing hanger is used it is oriented with respect to the guideposts, landed, locked in place and the production packer is set. The pressure integrity of the tubing string, tubing hanger to wellhead seals and the production packer are then tested. The operation of the subsurface safety valve is also tested.
Wireline plugs are set in the tailpipe of the packer and the tubing hanger and the completion riser is unlatched from the tubing hanger and retrieved. There are now sufficient barriers to flow to allow the BOP and drilling riser system to be removed safely.
1.10 Removal of the BOP STAck and Installation of the Xmas Tree.
The BOP stack is unlatched from the wellhead and the stack and riser system is retrieved.
The Xmas tree is picked up on a completion riser assembly which consists of:
(i) A hydraulic connector which latches onto and seals on the tree manifold,
(ii) A wireline BOP stack which allow the well to be shut in if an emergency situation develops whilst conducting subsequent wireline operations
(iii) An Emergency disconnect package which latches onto the top of the BOP stack (allowing the EDP to be disconnected from the BOP stack and retrieved on the riser if the rig has to move off location for any reason)
(iv) A stress joint to accomodate the movement of the riser when working on the well.
(v) The completion Riser
(vi) A terminal head to allow surface shutin of the well during flowtesting or workover operations
(vii) A workover control system
The control system allows the operation of the wellhead and riser connectors, all of the major valves on the tree and the subsurface safety valve. It also provides conduits for testing various seals such as the cavity between the tubing hanger and Xmas tree.
When the tree has been landed the wellhead connector is energised and all of the major functions are tested. The Xmas tree to wellhead seals and riser system are then tested for pressure integrity.
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The wireline plugs are retrieved from the tubing string. The perforating guns are run and the production casing is perforated. Flow from the well is then initiated and the well is cleaned up and tested. The flow can be initiated in a number of ways. The tubing can be run partially filled, coiled tubing can be used to circulate light fluid or Nitrogen or a circulating device in the tubing string can be opened and the tubing circulated to lightweight fluid prior to perforating.