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

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1.1   CASING HEADS

This is the first section of any well to be completed, and is the responsible of the suspension of the first casing string,by means of an accessory called casing hanger placed inside the casing head's bowl; it has an extraordinary ability to practically bite hard the casing string suspended(due to the sharp slips inside) and it's resistance must be equal or superior to the weight of the heaviest casing string suspended. At the same time the casing head has to support the sections that are above; so you can imagine the amount of load that this element has to deal with.The annulus seal inside the casing head's bowl is made by the casing hanger's weight supported, that is transferred to it due to the casing tube string suspended, in that way the elastomeric seal is energized by compression; when also in some cases happens there is no weigh enough in the casing string suspended and the situation becomes important, the seal doesn't work properly and in this situation another casing hanger's design must be used quickly; that one is the slip bowl type, with an pack-off on top of it, energized by Allen screws. The operation of change one casing hanger for the other under this circumstances is relatively easy, and down time operation has to be taken in count. Image ahead shows a Casing Hanger DMC-C-22.

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Typically the Casing Heads are made of forged steel AISI-4140/30 of 60 K minimum yield material condition up to 75 K, in cases where loads are extreme as a 20" OD Casing or a 21-1/4" OD Casing. In the bottom of this element typically are a so called Socket Weld (SW) prep. attachment, where it has to be welded to the ground conductor, and must be a 1/2" L.P. port in the bottom for the hydrotest of the this weld on site.

Other configurations may vary from SW. to a Threaded ones, where typically a Buttress Thread, are widely used, and in rare cases a quick attachment are some times used, like a clamp that many trade marks has in the market.            

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The outlets of this elements are typically studded, but also may come in threaded version 2" L.P. The section "A" right position, has studded outlets, and slick bore bowl type, plus note the base plate of 40" OD Diameter shop welded, 11-5000 PSI WP API FLG. top.

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Casing TBG 7-1/16-3M PSI w/two 2" LP Threaded outlets, and a   Valve model "SLBG" connected with a nipple 2" LP THD both        ends. This Casing TBG has in the top flange four lockdown         screws for various purpose, for instance set down a tubing         hanger various styles (Wrap-around or Threaded for                   Suspension)    and also for locking in place a Bowl             Protector  .This assembly is suitable for Pumping Wellheads     where the pressure of the oil reservoir is low or inexistent, and a     Subsurface Pump or other   device needs to be installed for             extract the oil.

 

Bottom drawing is a detail of the Socket Weld magnified, for you to look at it, for more details, and about the Welding Procedure Please Contact US!!!!

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            This kind of work has to be performed ON SITE, due to the first conductor is already planted in ground, and generally it is now cemented, from the bottom shoe, up to the top.This welding work on site has to be performed, carefully, because, it means sparks, and that mean explosion risk, take proper precaution , and a Safety Crew has to be first on site, to check, the Security of the Well , free of gas, by approved procedure that any company MUST HAVE, without any exception.

After assuring the security working conditions of the the well's site; the welder makes his part, and a preheating procedure starts;  next welding with proper electrodes, and then when finish has to be performed a stress relief of the weld, typically by using a wraparound device that has an internal electrical resistance(HOT HEED style), connected to the A/C generators of the rig .

Now is time to air cool the welded area, and then: hydrotest the bottom connection formed, assuring no leaks detected , may require also penetrants liquids(Magnaflux style) or others inspections  per customer demand and policy.

Updated on:01/11/04Copyright @2003 Daniele Molaro Consulting

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