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Casing temperature derating
05 April 2017
Hi All!
We are drilling exploration wells down to 6200m (20 340 ft) and temperature goes up to 142 C (288 F). Already drilled 2 wells and we are planning to make some changes to the original drilling program, and i would like to introduce temperature derating factor for casing design. I've contacted to the pipe suppliers but not clear firm answer to the question so far. 
From your experience, should we consider temperature derating, if so could you share with some figures?

6 answer(s)
JDDrouin
QA/QC Subsea Wellhead Specialist
SPREADAssociates
Total Posts: 83
Join Date: 06/05/09
Askhat,


Unless specific tests (charpy, tensile, etc) have been performed on the casing grade planned to be used, it's unlikely you can find a definitive answer.

However, structural steel, typically increases in strength from tests made at 70deg F up to ~425deg F, so it's unlikely casing grade steel will respond differently.


Dominic
Harald
Drilling Supt
Amni Int'l PetDevCo
Total Posts: 21
Join Date: 13/09/07
Try John McDowell of Rox. His LinkedIn is https://www.linkedin.com/in/john-mcdowell-4b92ab15/

He will be able to give you an answer on this ...

Best regards,
Harald Benning.


Askhat
Well Test Engineer
ALMEX PLUS
Total Posts: 16
Join Date: 24/12/14
David,
Actually I started this subject because right now I am responsible for well test operations and during the discussion on perforation strategy I'd asked our well designers about collapse resistance for dynamic underbalance perforation and found out that there missing information for temperature derating.
I've got some infomation from the pipe supplier but not sure if our software takes into account the right values.


Askhat
Well Test Engineer
ALMEX PLUS
Total Posts: 16
Join Date: 24/12/14
Thank you Gaz for your valuable input!
david.vavasseur
HPHT Drilling Engineering Team Lead
Maersk Oil
Total Posts: 24
Join Date: 22/07/12

Ashkat


Are you planning to do a DST ? What are your circulating temperatures ? Are you using a mud cooler ?

Simple answer is yes, it would be wise to use temperature deration, in your design. For Carbon steel, it is as per Gaz reply. If you are using chrome pipe or CRA, be extremely careful as deration will be different (more severe).

Another thing to take into consideration is connections for your intermediate string and production strings. If you produce well, elevated temperature close to surface will :

- create wellhead growth (Is your surface strings cement designed to cope with temperature differential)

- Put strings in compression : be extremely carefull to tri-axial loading at top of cement for your intermediate string and production string - this is likely where combination of loads will get them to fail.

Quick verification in a reputable software will allow you to sense check if any issue is to be forecasted (as will take into account standard deration for steel and basic temperature profiles).


Hope this helps


David


Hope this help



ghrahchamani@yahoo.c
Drilling Consultant
Canpart
Total Posts: 20
Join Date: 08/01/16
Hello Ashkat,

The yield strength of the casing will be de-rated at higher temperatures. The default value in some of casing design software's is that the yield strength de-rating factor is 1 at 68 °F and at 500 °F the de-rating factor will be 0.87. The software assumes a linear reduction in the yield strength as a function of
temperature with a slope of 0.03 %/°F. In reality, the yield strength does not decrease linearly with the temperature increase.(Please see attached de-rating chart)
The de-rating factors can be received from the manufacturer of the casing.
Based on the attached chart, you can see that for your situation (142 Deg C) the de-rating factor for YS is around 0.84 and is not  linear.

Once the YS is de-rated based on the actual temperature, the collapse pressure will also be de-rated based on  the attached formula. In this formula Yp is the Yeild strength of the casing and in this scenario we should use the de-rated YS.

Hope this helps.
Gaz
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