DANIELE MOLARO CONSULTING

Oilfield Consultant in Surface and Subsea Wellheads Equipment, Christmas Trees,Flow Control Equipment,Seals(Elastomerics & Metal-to-Metal)                     Contact me NEW E-mail: country45ve@yahoo.com

8.4)  Christmas Tree

After the casing programs and the tubing hanger had been land into the wellhead, the next steep is to plug the tubing hanger and at this time deploy the Christmas Tree, this operation is hazardous and the reason is to leave the tubing hanger plugged, while you are trying to deploy a very heavy stuff of equipment that in general way look like the images ahead, at this stage the security of the well depends on the plug in the tubing hanger, and if something goes wrong there is no immediate way to control it . The way to complete a Subsea Well in this stage can be arranged in two options: an exploratory well, or a producer one. In the first option there is a common criteria to hook-up the well with a Vertical Christmas Tree, like the one shown in images ahead, but if there is a production well being completed the best decision is an Horizontal Christmas Tree; in the first you have the Tubing Hanger landing into the Wellhead, but in the second you'll be having a Tubing Hanger that lands into the Christmas Tree, with a dual bore typically a 5" production bore X 2" Annulus Control Bore. The Horizontal Christmas Tree has advantages and disadvantages for example they are limited to 10,000 PSI WP because of the risk of vibration caused for the oil pressure coming out of the reservoir, but if that working pressure is what you expect to handle or less this assembly is really practical due to the less time to make the completion and the reentry of the well.   There is a orientation groove into the tubing hanger, that orients the Christmas Tree as planned, and also make possible the connections of hydraulic and electro-signal. The tubing hanger seals into the bottom of the Christmas Tree, and is tight assured, by means an interface connection typically a Vetco H4 also there is many others made by other manufacturers of Subsea Equipment.

dmc s21   dmc s22

Notice as shown in this images dmcs21 & 22, in this operations we can appreciate a Marine Riser that make possible the connection with the drilling ship, as well as the hydraulics, and electro-signals; there is also a EDP (Emergency Disconnection Package), then the Wireline BOP that makes possible the retrieve of the tubing hanger plug and other control functions in the bore of the tubing, and then the Christmas Tree. This equipment's configuration is  general; may vary from one location to another, nevertheless this information brings  you the idea that they can work like  modular packages, one on top of the other, and makes possible the full control of the operations until finally removed, and the Christmas Tree is installed. Then the basic operations are: check assembly from leaking points, check the integrity of the Wellheads and Christmas Tree, check for good response of the Christmas Tree via Hydraulic commands and Electro-signals and if every valve responds (Opens & Close) the next steep will be removing plug into the tubing hanger and run the Wireline to the downhole. After the tubing is opened downhole the oil comes up and it is conducted to the CCM (Central Control Manifold) by means of a very specials tubes flexible, covered with insulant material that keeps the loss of temperature to a minimal, insulations common used are syntactic foam ( a foam epoxy resin made). Generally the CCM is the collecting point of many productive wells having as well as the total control of them.

  

Then the oil comes from the CCM to a series of flexible tubes connected and left floating at a certain water dept called Risers Systems, there are various  configuration for possible: The Lazy-S; Lazy Wave; Steep-S Configuration; Steep Wave Configuration; Steel Catenary; etc. All that systems are responsible to bring to the FPSO the oil from the bottom of the seabed , they are flexible and thermally insulated to avoid problems in the flow of the crude (paraffin formation).

 

Updated on:02/21/05Copyright @2003 Daniele Molaro Consulting

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