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BOP closed accidentally
25 November 2020

It happened in one of the rigs of an Algerian drilling contractor, while pulling out of the hole suddenly the weight increased and pipe was cut due to the high overpull applied. The investigation mentioned that the pipe rams was closed during the POOH, and this was the main cause getting the pipe cut.

The spread words on the rig and in the office are saying that the BOP was closed accidentally by itself.

I am a well control instructor, and couldn't believe it.

Please if someone could and answer to that: would the BOP close accidentally by itself? (Also they are saying that the control unit pumps run every one minute....!!!!!?)



Note from Dave Taylor (moderator): We have a long list of professional associates who can conduct a full review/investigation.  If required, contact me on: dave @rp-squared.con
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9 answer(s)
Drilling Engineer
Total Posts: 1
Join Date: 18/02/20
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.

The EHBS system was investigated in attempt to determine the root of the failure and the BOP/LMRP was function tested and serviced.

The software was analysed line by line and it was proven that the software could not fire the EHBS without external input from surface. On surface the EHBS sequence can be fired from the EDS sequence or the EHBS test mode. The retrieved data indicates that the EDS sequence was not activated. Therefore the only possibility is that the EHBS test mode key was turned hence activating the system. If the key is only turned 35 degrees and flicked quickly it will return to the normal position but still fire the EHBS sequence. This action will also not register on the event logger, hence there will be no record of the event.

Maintenance activities performed on the BOP during this time included the ram blocks being removed and re-dressed, chart testing of the hydraulic operators, a new flex joint and LMRP connector was installed, the mandrel on the lower annular upper housing was replaced and the blue and yellow MUX cables were also replaced.

The decision was made to continue drilling with ROV intervention required to complete the EHBS sequence.
Drilling Coach / Wewll Control Instructor
Total Posts: 15
Join Date: 23/03/14
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: 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.
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Drilling Consultant
SPREAD Associates
Total Posts: 46
Join Date: 11/02/09
Morning Yahia

It sounds like this was a land rig.  I'd start with replacing the operating valve for that ram unit.  Pressure test it to see if there is a leak to the closing side.  Do not strip it down until you've finished pressure testing, you will disturb seals and possibly destroy evidence.

Please post any findings you make.

Regards, Steve
SPREAD Associates
Total Posts: 164
Join Date: 05/03/08
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

Well Engineer (Contract)
Total Posts: 1
Join Date: 21/06/19
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. 

Unfortunately I wasn't able to get any information from the investigation but there were certainly a lot of sceptics
Well Engineer
Total Posts: 25
Join Date: 17/09/07
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


Senior Drilling Engineer
Pakistan Petroleum Ltd
Total Posts: 34
Join Date: 02/08/15
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. 
Managing Director (
Relentless Pursuit Of Perfection Ltd.
Total Posts: 484
Join Date: 10/01/05
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


SPREAD Associates
Total Posts: 17
Join Date: 26/09/13
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.
Posted by

Sidi Yahia Berrouigat

Drilling Coach / Wewll Control Instructor


Total Posts: 15
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