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Large bore production casing
26 July 2019

Hi to All.

I would like to share with you a possible casing design for a  Deep-water Development well for a shallow gas reservoir.

Usually the standard casing design are the following:

36” jetting

20”-Swedge-13 5/8”

9 5/8” – 10 ¾”

open hole /GP

Upper Completion (UC)

Looking to the new gas tight 20” connectors, it might possible to remove  a string from the well architecture, by incorporating a casing design MTM (Metal-to-Metal)  as following:

36” jetting

20” MTM  ( gas tight 6500 psi burst) -Swedge-13 5/8” MTS ( gas tight )

Liner 9 5/8”

open hole /GP


I would like to ask you if any team in the world  has implemented (or is close to implementing) a design like this:   production tubing run inside the 20” gas tight casing.

Things like wellhead and tree design also spring to mind.

If anyone has some feedback, it would be greatly appreciated.


2 answer(s)
Senior Drilling Engineer
SPREAD Associates
Total Posts: 4
Join Date: 22/08/14

Hi Ibrahim

  • On the single 'A' annulus on a long term producing well, my recommendation would be no for the following reasons
  • No long term data on reliability of MTM 20" seal to hold an annular pressure for a prolonged period of time 
  • The 20" is there for wellhead support
  • I believe it asks a lot to have it as 'A. annulus.  
  • Ability to reach a problem well in a sufficient period of time to isolate it and make it safe.
  •  If a pressure builds in the 'A' annulus and there is a leak then that’s leaking at your surface casing shoe and therefore likely your conductor.

It is a short term financial gain to have the surface casing as an 'A' annulus with longer term consequences if a leak occurs.


Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 461
Join Date: 10/01/05

Bottom line is 10-15k high pressure wellhead housings can be integrated to suit these requests in many regions. Down to 9-5/8" that I have experienced.

Been therefore done for decades in several regions.

Just need to assure quality controls are in place during manufacture implementation and assurance as end result would generally not be API. But would essentially be verified in the same way ultimately through a pressure test 
and or any FEA needed etc.


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