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BOP Failures during DST Job
02 December 2011
We have experienced a series of BOP leaks during DST Job.
We are utilizing 13-5/8" x 10 NOV Shaffer BOP.
Since the DST job in August, we have had a series of failures as mentioned below:
1). leak from Shear ram bonnet
2). Leak of 3-1/2"-5-1/2" Variable ram,
3). Leak of 13-5/8" x 5K Spherical Annular BOP
4). Leakof 3-1/16" X 10k Kill HCR valve.
Has anyone experienced this sort of BOP failures- what did u do to prevent it?

5 answer(s)
Consultant [retired Shell staff]
Total Posts: 249
Join Date: 02/09/05
The multitude of leaks may indicate a change in the fluid inside the wellbore/BOP. Most seals accept normal drilling muds but are not so effective with more sophisticated fluids.

So lab tests may reveal if rhe seals are compatible with the fluids AND additives in use.

The only leak which is not a surprise is the variable bore ram, indeed very prone to leak, particularly on the smaller pipe OD..

Similarly, the bag preventer reliability goes up with the size of the pipe in the middle. On no account should be tested as a complete shut off... then it can become a complete failure.

Unable to comment on the HCR valve as I´m not aware of the model and make of it.

PS The factory acceptance test of the BOP may help in identifying the sources of problems by zooming in on the differences FAT/Actual testing conditions.
Snr. Completion Eng
Total Posts: 2
Join Date: 09/03/11
Hi there Gents,

Such BOP failure (multiple) are very uncommon, has the BOP it´s subjected to multiple function and P/T. Usually, prior to any DST ( extended or ”œshort”) a BOP function and P/T has to be performed, in order to certify the integrity of the equipment.

Therefore, I would suggest the following:

Make sure BOP sealing elements are within Temperature specs required during flow periods, especially if No TH is being used and Variable / Fixed Rams are being used as the secondary barrier after the DST packer downhole. (Well-Cat modeling to confirm this). It is not advisable to use BOP rams as primary surface barriers in ”œHT” wells.

Make sure that, technique being used it´s the most appropriate 8 underbalanced / Overbalance. Each individual case has its own benefits and down side especially in a surface leak scenario.

Best Regards,

Jose M Rodrigues
Total Posts: 10
Join Date: 26/06/11

I have never heard of quite so many failures on one BOP. What was the time span of the failures?
Has the BOP been subjected to any form of corrosive fluid ? if so do you use synthetic components or rubber components? Otherwise it could,be a maintenance issue. Or has the BOP been subjected to testing to often which can have an adverse effect on all parts.
Are spares kept in an air conditioned room as per recommendation? Does anyone check to make sure they are still in good order.

Nick Appleyard
Total Posts: 12
Join Date: 08/05/09
Is the BOP Certified? Sounds like a maintenance issue. When were seals last replaced etc. What's the pressure rating.
Drilling Supervisor
Total Posts: 2
Join Date: 19/07/11

Doesn't sound too good - if you can tell us a few details it might help to diagnose the problem:

Is the BOP on a jack-up rig?
How old is the equipment?
How long had the elastomers been in service?
Are replacement elastomers all stored in dark air-conditioned conditions with "use-by" dates?
Were elastomers OEM or reputable supplier?
Were elastomers rated to correct temperature?
Were BOPs tested regularly and witnessed, charts kept on file?
Have you identified where the HCR leaked - was it the valve seat, a washed out valve body or a failed seal ring?

The fact that the failures were of several different types suggests a problem with maintenance - in that case a 3rd party audit of the equipment and maintenance standards would be a good idea for a start.

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