Is it possible to connect 18 3/4" BOP on wellhead of 13 3/8" or 13 5/8" on a platform well from Jack-up rig?
If possible what are/is possible way/s and support system required to connect 18 3/4" BOP to wellhead?
And also all the risk involved in it?
If any diagrammatic or pictorial view can be shared would be good for understanding.
Thank YOU all for reading the query.
Yes. It was PVD 2 Rig, back in 2010, in Vietnam.
That was the only BOP they had on the Rig. If you want anything out of the Rig equipment, you have to pay for the rental of 13-5/8" BOP from the vendor.
Similarly, they had only 5-7/8" DP. You want 5" DP for smaller hole, you have to pay for the rental.
Of course, it is possible to connect an 18 3/4" preventor onto a 13 5/8" housing.
My recommendation is to remove the bottom 18 3/4" wellhead connector and replace it by a 13 5/8" wellhead connector with non-standard top - a crossover 13 5/8" x 18 3/4" .
This to reduce the height of the assembly as much as possible knowing that the 18 3/4" BOP on its own is taller than the 13 5/8" one.
Such an assembly weighs much more, so - not only you lose deck load directly but also more deck deckload indirectly, as tensioning is required.
The 13 5/8" housing - NOT the BOP - should be suspended from the tensioners. This to keep the desired preload onto the BOP ring gaskets.
In most short campaign, the Operator will use whatever supplied by the Drilling Contractor such as 18-3/4" BOP. I do prefer 13-5/8" BOP.
Advantage of the 18-3/4" BOP is that if you have a 16" casing, then you don't have to change BOP from 18-3/4" to 13-5/8" which takes long hours depending on the handling system and the crew efficiency.
Disadvantage of 18-3/4" BOP is the weight, which is difficult to push or pull when nippling up. If it sit on the ring gasket, it will damage the ring gasket. Besides, the AV is very slow due to large ID of the BOP which reduce the hole cleaning efficiency.
I am just wondering under what circumstances or type of well, this would make sense, other than no functioning 13 5/8" BOP to available to N/U?
It is quite a common practice to connect the 18-3/4" BOP onto 13-5/8" wellhead on Jack-up Rig. You will need a Drilling Adaptor Spool (DAS) which acts like a crossover from the Wellhead to the BOP "connection". Wellhead company will give you the spec of his connection (such as NT2 connection) and Drilling Contractor will give you the spec at the bottom of the BOP or Riser.
The heavy BOP can be supported by BOP crane which is located at the substructure. Some operator prefer to hand the BOP with 4 hydraulic arms.
Will try to get you the drawing if I can find some old Drilling Programme.