Great evident case study Allan.
I can take us back much further. To what I always suspected are the root causes to these issues.
Late 80’s one N Sea operator had 11 semis drilling subsea wells.
Majority of supervisors knew why it is so important not to drill a Y shaped top hole on the seabed in environments where you cannot jet. North Atlantic etc.
Ie can accelerate failure of wellhead ssbop marine risers systems and top up cement jobs response reaction and cure time and money would be needed
One particular well drilled in this period was so badly Y’d that when SSBOP was installed bop wobbled about. So much that hazard and risk further assessed resulted in well had to be respudded. At Significant loss and added expense.
Rather than get to the root causes and take a more proactive and preventative way to resolve the problem?.
‘Titus top up systemS evolved‘ that then became the Standard company norm. That others then also adopted. Management incompetence.
Note: Despite evident well facts that 70-80 wells had also been drilled by that operator in this period that did not need Cement top ups.
Whether wells needed or not top up Cementation was, has and is still being used to my knowledge?
30-40 years later? and entering into abandonment of topped up wells. Where I suspect the issue resides!
Because we predicted this 30 years ago that topped up wells will probably need a lot of ROV cement evacuation to remove Car parks of cement on the seabed from these wells that we observed :).
Where future P&A hazard and risks we did inform operators about.
My own experience of having to P&A a particular Y drilled top hole well ( that we did not spud) where 4 top ups resulted to fill in the Y cavern at the seabed. Fact was the main contributor to the added 4 days required when abandoning vs expected standard norm.
Watch this space. West of Shetland In particular we suspect? ROV pilots shall get plenty of time in the chair excavating cement :) When final P&A of these wells Comes around. .
I suggest RP2 initiates a separate learning evidence gathering sharing thread on final well abandonment of wells that had top ups cementation and those that did not.
Then based on evident conclusions, assure best practices and learning is then translated and sustained into future subsea wells to be drilled and cemented?
Ie drill perfect cylinders, from seabed, avoid Y shaped caverns, assuring best drilling practices are used / applied in the first instance?
Finally there is a further discussion needed where CAN’s ie conductor anchor nodes, are now being used in areas where we know cement cannot be brought to the seabed. Eg First 10-15m of formations are too weak to take a normal weighted cement slurry.
Where either a light weight slurry is needed an/or a foundation pipe is required ie a 6m Diameter x 6-8-10-15m long CAN dependent on subsurface conditions that exists.
Offering a better solution to the problem vs Y shaped wells, top up cementations And or repeatedly failed jetting jobs.
Where every year we are noting more CAN’s being run for all the right reasons?
Further food for thought for today’s drilling engineers.