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Casing Connection Strength Envelope(CSE) (xls) from OCTG Manufacture application in Wellcat Csg Design
19 February 2020

During assurance of complex/critical wells it become practice for me to test the connection strength envolope (CSE) xls to be uploaded in Wellcat (as shown in wellcat result) but some operator dont ask OCTG manufacture these data and miss some times to test on connection envolope ? How to mitigate these problem? What are guidlines on the same? Co like Shell spend money of specimen testing but other operator rely completely on OCTG manufacture?

Dear expert whats your view/exp on the same?


Documents uploaded by user:
1 Csg Design Result.jpg
2 answer(s)
Drilling Engineer
Tullow Oil Plc
Total Posts: 9
Join Date: 06/02/12

Hi Mahesh,

For years we have been using our standard connections and doing tri-axial design on the envelope of the tubular, but only considering uniaxial for connection ratings. Part of the triaxial design safety factor (for instance increasing from 1.15 to 1.30) being applied is attributable to the connection envelope only being tested to up to 90%. I believe this way of compensating for the CSE has been the stance for known T&C connection envelopes where the company has considered the shape of the envelopes at some stage prior to putting them on the list of company standard connections.

Recently, moving to new semi-flush connections, that aren't claiming to be 100% of pipe body ratings, the shape of the CSE supplied by the vendor can be much more limiting in certain areas. Without the time and money to have proprietary tests, we're reliant on the CSEs provided by the vendor. The CSE maybe based on FEA and interpolated from physical tests on similar spec pipe. Also, the CSEs seems to be based on 100% theoretical rating rather than physical testing points to 90%. We're checking what the closest physical connection test was, taking the vendor supplied CSEs and applying the same conservative triaxial design SF (1.3) that includes an allowance to diminish pipe ratings to 90% for the connection.

If we receive a connection test sheet (which we haven't) that was based on physical test points then we would consider removing the extra allowance for the connection and using a lower SF (around 1.15).

Sorry, not an expert answer, but an approach from someone in a similar position to yourself.



Managing director Punch Energy Services
Punch Energy Services
Total Posts: 6
Join Date: 24/06/20
Hello Mahesh,

Guess if you are purchasing from a premium manufacturer the data they can provide is quite valid. These companies have quite an R&D department and testing facilities.

You can always check with the manufacturer according which standards the connections have been tested.

Another thing companies could perhaps do is to carry out a FEA.
Perhaps there are external companies or manufacturers who could do that for you against acceptable cost.

Best regards,
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