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Wellhead
26 April 2018
Hi dear all,
I have a question regarding wellhead pressure test (integrity test). Is there any standard procedure for required test pressure and duration for: 
1- Between primary and secondary seal 
2- Between secondary seals
and also required pressure to energize elastomer seals.
I couldn't find procedure (e.g 80% of casing collapse pressure) in the API-6A. 
Appreciate if you help me. 
Warm Regards
4 answer(s)
Jov
Senior Drilling Engineer
NRG Well Management Ltd
Total Posts: 17
Join Date: 01/09/15
Hi Saeed,
Did the above suggestions help?

Regards
Jov
SCollard
Director
Welltrain Limited
Total Posts: 7
Join Date: 09/12/09

Saeed,

 Apologies,   a couple of errors in my original reply:

“For pressure from below the casing hanger (i.e. pressure that might develop between the casing hung from the casing hanger and the previously installed hanger), the second barrier is provided by the Primary Seal”  should read:

“For pressure from below the casing hanger (i.e. pressure that might develop between the casing hung from the casing hanger and the previously installed casing), the second barrier is provided by the Primary Seal,”

 

“The pressure rating of the Secondary Seal(s) is the same as the pressure rating of the TOP flange on the wellhead spool” should read:

“The pressure rating of the Secondary Seal(s) is the same as the pressure rating of the TOP flange on the wellhead spool that is being installed”.

"Test of casing, spool side outlet valves etc and the upper secondary seal from above.  During this test, the upper test port should be open to check for a leaking top secondary seal" should read:

"Test of casing hanger (using cup-type tester installed in top of casing), spool side outlet valves etc and the upper secondary seal from above.  During this test, the upper test port should be open to check for a leaking top secondary seal"

I hope this improves clarity!

Steve


SCollard
Director
Welltrain Limited
Total Posts: 7
Join Date: 09/12/09

Saeed,

I am assuming you are talking about API Spool Type Wellheads.

There should always be two barriers between potential pressure inside a wellhead and the outside world.  With a spool type of wellhead, one of those barriers may be the ring gasket in the flange between the two spools.   I say “may” as this ring gasket is rated to the pressure of the BOTTOM  flange connection on the wellhead spool.  More of this later!

For pressure from below the casing hanger (i.e. pressure that might develop between the casing hung from the casing hanger and the previously installed hanger), the second barrier is provided by the Primary Seal,  This is usually rated to the pressure rating of the TOP flange connection of the spool it is hung off in. 

For pressure that may develop inside the casing suspended from the hanger , the second barrier is provided by the Secondary Seal or Seals.  These seals are intended to hold pressure from above – preventing this pressure reaching the ring gasket between the two spools.  The pressure rating of the Secondary Seal(s) is the same as the pressure rating of the TOP flange on the wellhead spool.

Wellhead pressures increase as the well is deepened and so the pressure rating of the successive wellhead connections may also increases.  Thus the top flange (and body of the spool) may have a higher pressure rating than the bottom flange. (e.g. 18-5/8” 5,000psi x 13-5/8” 10,000psi).

Where the top flange has a higher pressure rating, a pressure may develop inside the casing that is greater than the pressure rating of the bottom flange and it’s ring gasket.  So,  you require TWO secondary seals to provide two barriers between the inside of the casing and this flange.  In this case there will also be two test ports on the bottom flange of the wellhead; a lower one leading to the cavity formed by secondary seal, primary seal, casing/mandrel and ring gasket and an upper one leading to the cavity between the secondary seals.

All separate seals should be tested independently and, where possible, in the direction they are intended to hold pressure.  In practise, the primary seal is a single rubber element and is usually pressure tested from above in combination with the ring gasket of the flange.

Best practise is to pressure test primary seals to the pressure rating of the Lower Flange and Secondary Seals to either the  Maximum Anticipated Wellhead Pressure for the casing that has been hung off or to the pressure that you plan to pressure test this casing to. 

Different test protocols are used when testing primary and secondary seals.  In all cases there should be an initial lower pressure test to 200-300psi then a test to the full test pressure.

Where the top and bottom flanges if the spool you have just installed are the same pressure rating there are two tests.

  1. Test through the test port to test primary seal and ring gasket. 
  2. Test of casing, spool side outlet valves etc and the secondary seal from above.  During this test, the test port should be open to check for a leaking secondary seal.

Where the top flange had a higher pressure rating there are three tests:

  1. Test to pressure rating of lower flange through the lower test port to test primary seal and ring gasket. 
  2. Test to MAWHP / Casing test pressure between secondary seals through upper test port.  This tests the lower secondary seal from above.  During this test, lower test port should be OPEN to prevent build up of excessive pressure against the ring gasket should the lower secondary seal fail.
  3. Test of casing, spool side outlet valves etc and the upper secondary seal from above.  During this test, the upper test port should be open to check for a leaking top secondary seal.

All pressure tests exert a collapse pressure on the casing or seal neck if using a mandrel type hanger, it is therefore recommended that test pressures should never exceed 70% of the API minimum collapse rating.  If a higher test pressure is required then backup pressure will need to be applied to the inside of the casing by installing a cup-type tester inside the casing and applying pressure between it and the BOPs.

Where a weight set slip/seal assembly has been used, some extra care is required.  There is a short section of casing between the slips and the primary seal that is under the landing tension of the casing that will also see a collapse load from the pressure test applied to the primary seal.  In this case,  the casing collapse rating needs to be derated for tension using the method proscribed in API Bulletin 5C2 / ISO Standard 11960.

 I hope this is of help.  Feel free to contact me should you require any more information

Jov
Senior Drilling Engineer
NRG Well Management Ltd
Total Posts: 17
Join Date: 01/09/15
API STD 53 4th Edition 2012
Section 6.5.3 Test Criteria
Sub Section 6.5.3.2.1 - All BOP prevention components that can be exposed to well pressure shall be tested to a low pressure between 250psi to 350psi and then to a high pressure test.
Subsection 6.5.3.2.2 - When performing the low pressure test, don ont apply high pressure and bleed down to thelow test pressure.
Sub section 6.5.3.2.4 A stabilised low and high pressure test shall be maintained for atleast 5mins with no visible leakage.

Operators normally use the same prescription while testing wellheads and other well related equipment.API - 6A which you have referred to is for equipment specification prior to installation.


Hope this helps.
Regards
 
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