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Experience with stabbing and M/U of 20" BTC connections on a semi-submersible
26 November 2020
Dear members

We'd value your experience (and opinion) on this topic.

As preparations for an upcoming virtual (online) DWOP, I'm reading a Drilling Programme that has a mixed string of 20" casing, including 24 jjoints of 94 lb/ft with  BTC connections. The well will be drilled off a moored semi-sub.

I am concerned about being able to stab and M/U these connections (to the visual marks) safely and efficiently.  I recall, in the North Sea, that we even had problems with the lighter 13-3/8" 68 lb/ft casing and ended up adopting a No-Cross Coupling design.

Perhaps I'm being over-anxious, but I'd value input from the forum, especially those who have been personally involved in running such large strings on a floating rig.



9 answer(s)
SPREAD Associates
Total Posts: 7
Join Date: 07/08/09

I can’t offer a solution but a couple of considerations:

The time it takes to run the pipe, it will be subject to current, VIV (Vortex Induced Vibrations) etc;

If run offline the above is x2;

Weather window to run the string based on the above;

Hole conditions may drive all of the above, so plan properly.  Drill the section correctly, correct MW, correct procedures etc;

Be realistic, BTC pipe is used all over the world and has its place - always an application.  

Treat each well like an F1 car, the set up is different each time.



D&C Project Coordinator / Decommissioning
SPREAD Associates
Total Posts: 37
Join Date: 25/01/16
The key issue is to assess with Augmented Intelligence the selection of the casing connections. 

The HESQ Process Hazards must all be perceived relative to the well system and drilling system situations.  Opportunity to build a Cluster for collaboration in cooperation coaching project coordinators on best practices without considering cost or time. 

An ideology of reliability relative to HESQ Process Risk should prevail where any perspective could call a Dupont STOP and ALARP ideologies can be stored in a museum with tendering and negotiation in competition.  
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SPREAD Associates
Total Posts: 10
Join Date: 23/01/13
I totally agreed with many member's opinion that it is a bad idea to run 20" BTC casing in floater rig. I personally never tried the same. It is always better to run multi-thread  speciality coupling, like vetco/drill quip/ cameron casing

However, if there is some compulsion to run  20"BTC in floaters due to availability constraint, be prepared for long time in casing make up, there is no shortcut. Keep an watch on weather forecast for calm see. Good luck!!!
Managing director Punch Energy Services
Punch Energy Services
Total Posts: 18
Join Date: 24/06/20
Hi Dave,
Would better avoid running a mix string and BTC with risk of slow RIH.
People think they save money running a mixed string but often results in extra time spend and risks of string integrity. (string is only as strong as the weakest connection)
Have seen project drilled with mixed strings and teams spending additional hours due to equipment changes etc. Putting the extra hours on the project budget is not really a cost saving, although it could look like a saving from the material charge point of view.

Material with the DQ connectors for example can be excellent to run. Or Vetco or even BIG OMEGA.

Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 502
Join Date: 10/01/05

Mixed string of 20"
- 24 joints of 94 lb/ft with  BTC connections.
- drilled off a moored semi-sub (A floating rig (not a fixed installation)).

Best case scenario?
- Flat calm no rig movement.
- Every thing on hoisting and lifting equipment guarantees plumb centre.
- Box and pins have been meticulously cleaned and re-doped.
- Buttress can, in perfect lowest risked running conditions, be run from a floating vessel where it acts like a fixed installation. 
- As Scott points out but it will be painfully slow. (because it has to be turned anti-clock wise until it bumps.) 
- Then made up to required torque with triangles verified etc.
- Done as per above it is doable but rarely experienced on semi's 

Why? because things that can affect safety and performance. 
- Rule of thumb is that the-bigger-the-pipe the more-the-rig time and money you will lose if you can't get the pipe aligned and cross thread joints.
- Any Rig movement on a semi will not help/assist and increases several safety issues hazards risk.  
- And why few ever run buttress as a surface strings (e.g. I have never experienced this from a semi)
- 13⅜" intermediate strings? often. But we had so many issues so many times. Best solution was in fact to make up and RIH in stands because it was far easier to see if pipe was straight to stab this in. Plus we already had two connections made up off line to save us running time etc. 
- If Block and hoisting equipment is not plumb centre, you will have issues. 20" is not that easy to manipulate via a stabbing board.
- Some top drives have some wiggle room where you can adjust a tad! 

- If any of the above issues exist, you will increase the probably and risk of cross threading and shall have to lay out some joints.
- Pipe does not make up to torque and/or is way short of meeting triangle. You have to assess do you run this or lay the joint out! Remember your running this from a semi not a fixed rig.
- Laying out both joints is a very time consuming, extra handling task, with lots of safety handling issues arising.   (Always have enough spare joints on board.) Much bigger day rates!

- 20" is the surface string that will be run in open water? Where if you have any current present that can affect pipe movement, F = m x a, where  pipe can easily work its way loose and unscrew! Its buttress there is no anti rotation device!

- Mixed strings raises the biggest alarm bells of all, so i had better warn everyone of this.  

- Here assure you meticulously QA/QC the cross overs as numerous strings have been lost and dropped due to floating vessels and movement failures induced here. 
- Where you may need to decide (for insurance) if you need to weld buttress connections after they are made up so they cannot unscrew. (welding on pipe etc is generally a no-no.) !

In summary it can be done, but there are so many evident and valid reasons why we stopped running buttress, particularly on floating drilling units.

As this can too often end up in costly failures that is far more time and money (that the better grade of pipe cost differential ) from all safety well (barrier and integrity) effectiveness  and operating running efficiencies reasons. 

SPREAD Associates
Total Posts: 164
Join Date: 05/03/08
Hi Dave,

I've primarily run 20" BTC on land rigs.

The two big take aways I have are that it is painfully slow (4 jts an hour is a good rule of thumb) and the connection is very easy to cross-thread - often 2 or 3 joints are rejected because of this on what are normally very shallow casing runs.

On another JU job, we were asked to use some old 20" BTC that was in stock. We did a calculation on running times and showed that it would be more cost effective to get the casing rethreaded to Big Omega than try and run it as BTC.

If it's an possibility, I'd have a look at rethreading options.

All the best

Total Posts: 3
Join Date: 24/03/09
Hi Dave,

 It's rather dependent on the sea conditions. In Malaysia shallow water we ran 18⅝" casing using side door elevators without any problems in benign seas.

 As others have said a stabbing arm would be a big help.

 The CRT is probably overkill IMO.

 But its all perfectly possible.
Drilling Engineering and Planning Director
Total Posts: 12
Join Date: 13/02/12
We have experienced in Onshore Algeria some HSE (fatality and accident) and operation (casing parting) issue when running large diameter tubulars with BTC connection.

This connection has 4 tpi regardless the diameter so it’s quite prone to be cross-threaded for big diameter (more than 13 3/8”) which would reduce to down to 15% its tension so we had casing parting either while running in hole (pulling while having an obstruction) or while cementing during casing pressure testing.

I would suggest to use a stabbing guide like recommended by Mr. Andrew Hepburn and make sure that TRS operator respects the make up procedure to the triangle. 

TRS Customer Co-ordinator
Total Posts: 1
Join Date: 05/05/20



Historically the 20" we have ran in the North Sea has been of a 1/4 or 3/8 turn for make up. So no issues were observed with the stabbing and make up of these connections. 

The concerns raised could be mitigated by using a mechanical stab-master or the use of the rigs drill pipe racking arm to keep the casing central.

As always we would recommend use of stab-in guides these would usually be supplied by the TRS provider.

Use of a CRT (Overdrive or other variant) would be highly beneficial also but this all depends on the length of string and requirement to wash casing down etc.

 Hope the above helps please feel free to reach out if any clarifications are required.


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