Hi all,

Was involved in a project where the casing shear rams inadvertently activated, shearing the drillpipe while drilling. Now it is public on a government database I can share what was reported below in the EOWR. Seems the root cause was the EHBS / Autoshear system.

"Drilling the 12 ¼” section resumed from 3948.0 - 3961.0 mMDRT, at 3961.0 mMDRT the driller experienced a sudden loss in pump pressure from 3,600 - 110 psi and decrease in string weight from 560 - 300 klb indicating the drill string had parted.. The drill string was then pulled to surface and from drill pipe tally and visual inspection of the sheared drill pipe it was confirmed that the drill string had been sheared by the casing shear rams. Initial investigation indicated that the EHBS system had malfunctioned. As the exact cause was unknown, it was decided to bleed off the subsea accumulators before running any assembly through the BOP. This would render the EHBS system inactive but still permit BOP control from surface within permissible operating times.

Hi folks, I thank everyone for your valuable replies and comments. I am not an employee of this company, but was called by a person who was there to help them understand what happened exactly. You may find more comments in this link here as someone shared the problem in LinkedIn: https://www.linkedin.com/posts/hany-metwally-2ba00769_wellabrcontrolabrlesson-iadc-iwcf-activity-6737682375167262720-uM8t. I am also attaching this SPE paper that says the BOP could close accidentally if the 4 ways valve is leaking, even I cannot believe it.

Hi Yahia,

The only time I am aware of a shear ram being accidently activated was on the High Seas Driller (a Semi Sub) in the early 1980's - and it happened twice, 7 days apart.

The investigation eventually established that both times it happened when the BOP control unit was receiving it's weekly wash down with a power washing unit.

I don't know the exact details, but apparently there was a loose gland of some sort which allowed the water to get in and caused a short circuit in the control system. This somehow activated the shear rams.

As Ruari has already pointed out, if the charge pumps are running almost continuously, then there is a large leak in the system somewhere and definitely not a sign of a well maintained unit.

But that does bring up one possibility - had the rams been activated for some reason a while before, and were slowly closing but the leak in the system meant that they took sometime to close enough to catch a tool joint?

Let us know what you find out!

Best Regards

Scott

Some years ago I had a very similar experience. I was a DD on a semi in the North Sea and while POOH with a dumb iron assembly the Pipe Rams supposedly closed and opened back "by themselves" causing the string to part. 

Hi Yahia

With reference to "control unit pumps run every one minute", I'd infer that this is the charge pumps kicking in.  When your accumulator pressure drops below 2,700psi (10%), the primary pumps kick in. Not a sign of a properly maintained system, although every minute  is excessive.....

Reference is API RP 53 Part 1 - Surface BOP

Cheers

Ruari

We've had a similar experience ~ 8 years ago when the driller pulled the pipe on a closed BOP after a shift change.

The previous shift driller failed to inform the new shift driller that the BOP was closed and hence the pipe parted.

So I guess it's pretty much the same issue in your case, because never heard that BOP can close on itself automatically. 

Hello Yahia

Years ago (almost sounds like "once upon a time"; like the start of a children's bedtime story), we had a similar experience on the Dunlin A platform in the North Sea.

The logging company had just pulled their tools to the rig floor when, suddenly, the lower section was chopped off by the shear rams.

This prompted an exhaustive (and expensive) fishing operation followed by an equally exhaustive and expensive review and testing of the BOP and control system to determine how this safety-critical piece of equipment could fail.

No cause could be found.

However, to satisfy the requirement to 'eliminate this from occurring again', all sorts of equipment modifications were proposed.

Just before the full re-engineering study started, someone pointed out something different about the day this happened.

The logging string that was 'always' run on the platform was fairly short and it was customary to close the blind-shear rams when the tool was on surface, to prevent it being dropped down the hole whilst being dis-assembled.

However, that day was the first run of a Super-combo type tool, which was much LONGER.

It was quickly realised that what had been a good practice (?) had become 'second nature'. You could almost argue that it was so natural that the person doing it might not even remember having done it.

So, there you have it.  Human error.  

We can argue about the root causes, but I would postulate that the "Human factors", element was at play that day.

From memory, there was no need to take disciplinary action.  The team discussed what actions to prevent this happening again.  Of course, it was highlighted at toolbox talks and the loggers-drillcrew communications were improved.  And the final precaution? A simple sign placed next to the blind-shear rams button, "Extra long wireline tool in the hole".

And, as all good stories end, "Everyone lived happily ever after"

_______

Nowadays, this falls under the remit of WOCRM (Well Ops Crew Resource Mgt).  We have seen our associates and team deliver awareness sessions at our (virtual and Face-to-face) workshops.

_______

Kind regards

Dave

In my 50+ years in drilling / workover operations never seen it happen. Even the modern touch finger controls have to have passwords, etc. someone inadvertently activated the PR and is not owning to it.