Shear Ram Configuration

18 November 2012 Hi Folks,

Currently working on a commissioning project for newbuild drillship which will come equipped with 2 x 7 Ram Cameron TL stacks.

We are discussing shear ram configuration with regards to BSR-BSR-CSR vs BSR-CSR-BSR and would like to get some feedback from members in terms of personal opinion and company policy.

Our initial plan had been to go BSR-BSR-CSR, however it appears that several contractors and operators are opting for BSR-CSR-BSR, based on the main advantage that there is less chance of having a tool joint across both sets of blinds. Shown below is a quote from someone at Cameron on the issue:

QUOTE:
We have previously installed the Shear Bonnets on two Rigs (Jack Ryan and CR Luigs) in the configuration of Blind-Blind-Casing. To my knowledge, no other Cameron Stacks were delivered in this configuration. 

The Cameron Standard Configuration for a Subsea BOP Stack with 3 Shear Cavities is Blind Shear - Casing Shear (Super Shear) - Blind Shear. We have this configuration currently installed on four Rigs in operation and will be installing this setup on 13 Rigs in the near future.

Blind-Casing Blind Pro:In discussions with our Customers, the desire to use Blind-Casing-Blind is that it provides the greatest insurance that you will not have a Tool Joint across both Blind Shear Rams in a shearing event. This is because the Casing Shear ram between the Blind Shears results in a cavity spaceout of 56.6” between the two Blind Shears (when all three shears are in a Triple ”˜TL´ BOP. If you install Blind-Blind-Casing, this distance between rams is 22.5” (if both shears are in the same BOP (Double or Triple)) resulting in a greater chance of hitting a tool joint with both Blind rams.

Blind-Casing-Blind Con: The Con is that if you hang-off and use the Casing Ram to shear, you must then use the Upper Blind Shear to seal the bore. If you were to use Blind-Blind-Casing, you could hang-off and then use either Blind Shear to seal the bore. 

Exxon, Shell, Petrobras, Transocean, Atwood all have policy dictating BSR-CSR-BSR with a variety of reasons for doing so.

END QUOTE.

After talking to several people in the industry, there seems to be mixed opinion as to what set-up is best. Ive also attached a word document which shows some positives and negatives for each scenario along with comments.

There is no mention /requirement in the BSEE CFR250 Final Rule or the draft version of API RP(S) 53 4th Edition.

Any feedback would be appreciated.

Cheers

Gary

Documents uploaded by user:

CSR placement (2) SPREAD.docx

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