Buttress : No-Cross Coupling
18 September 2009
At a DWOP that I facilitated this week, we were discussing the offline "stand-building" opportunities for an offshore multi-activity rig.
When we talked about making up Buttress casing off-line we were concerned about cross-threading, especially as we lowered the first 2 or 3 pre-M/U joints onto the final one. Any misalignment, eg due to vessel motion, would be magnified by the length of the "assembly" and could cause thread damage.
About 10 years ago, I came across a "No-Cross Coupling" that acted as a kind of enhanced stabbing guide. We used it successfully to M/U 20" housings, that had 13 3/8" BTC extensions, onto the casing string
Can anyone advise if this product is still made and where we can get it from ..
Also, does anyone have any other good ideas to prevent the threads getting crossed.
Relentless Pursuit of Perfection
The No Cross Coupling Connection was supplied by Dril-Quip - Aberdeen.
It was used when we drilled the slimhole well design: 30", 13.3/8"...
The 18.3/4" wellhead housing extension had a Squnch joint, which was made up to the Squnch Cross Over assembly.
The Cross Over assembly included the 20" x13.3/8" X/Over - 4ft - and a full joint of 13.3/8" casing with 13.3/8" BTC Pin.
The next 13.3/8" Jt had a BTC No Cross Coupling Box.
If you remember our lessons learnt: Pre-installation of the 20´´ x 13.3/8´´ X/Over (4 ft overall length) to a the top of a full joint of 13.3/8´´ casing allowed quick changover from 13.3/8´´ handling gear directly to 5´´ elevators to pick up the 18.3/4´´ wellhead housing assembly.
Thanks to all for your replies.
James, all I meant was that when we are making up casing off;line, we will have 3 x 40 ft joints already screwed together, will pick it up, install the 4th joint in the "rotary" and then lower the 120 ft long casing section to M/U to this final joint.
This makes a large pendulum and a 3 degree offset at the elevators will create a larger offset at the rotary with a 120 ft section.
I hope that makes sense ?
These have been used extensively to good effect in Australia on Australia's North West Shelf from a local supplier.
To help avoid cross-threading, start the thread using chain tongs. 18.3/4" housings are heavy to turn with a chan tong, but starting the thread with a power tong is much more likely to cause damage by cross threading.
Senior Drilling Supv
Not exactly the answer you are looking for, but please explain "Any misalignment, eg due to vessel motion, would be magnified by the length of the "assembly" and could cause thread damage." because the combination of geometry and length makes that impossible.