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Sub-sea BOP stack arrangement
21 July 2018
Hi , currently the sub-sea BOP stack arrangement for my exploration well is as follow: 

1) Annular Preventer
2) Annular Preventer
3) pipe Ram
4) Shear Ram
5) Variable Bore Ram
6) Pipe Ram.

I am just wondering if there is certain standard of sub-sea BOP stack ? or is it purely based on engineer's decision?
5 answer(s)
Consultant [retired Shell staff]
Total Posts: 248
Join Date: 02/09/05
I believe the geometry has a role to play not only because of hang-off procedures but also the space for the sheared stub above blind/shear rams.

I like to see if the BOP is constructed out of 2 two-ram preventers, or a 3-rams and one single BOP, etc.

DonĀ“t forget that in some cases to have hang off capabilities the spacing between rams has to be special.
Training/Project Manager
Myspread Users
Total Posts: 15
Join Date: 07/03/16

The drilling BOP Stack as you find configured for your current/next well may be an API BOP stack or a non-API BOP stack.

API Standard 53 'drives' and mandates the minimum requirements for a BOP stack - whether surface or subsea.  Providing the minimum mandated requirements are met, the stack is fit-for-purpose and may be considered 'legal for use'.  However..............

Many stacks are non-API, inferring that they are configured and constructed 'in excess of the minimum requirements'.  The general trend for deep and ultra deepwater is that the stack is supplied with a level of design redundancy that minimizes the need and probability of a stack retrieval due to a component failure that is contstrued as an unacceptable operational risk to the safety critical integrity of the well.

Many UDW stack refinements are actually featured in the architecture of the stack control system.
It is a common  prerogative of operators to exercise the BOP stack re-configuration change prior to drilling their well.  Most commonly, this will entail the change in position of BOP-mounted valves (choke/kill valves) with respect to BOP ram type preventers' outlets.

Hope this helps,  if you need further, please let me know.

Best Regards 

Dr P.A.Potter /  

D&C Project Coordinator / Decommissioning
Society of Petroleum Engineers
Total Posts: 18
Join Date: 25/01/16
Great point for discussion.  The layout of the BOP presented here seems pretty standard assuming there is a LMRP Connector between the two annulars.  The issue isn't about an engineer's decision.  It's about commingling the process hazards of the well system with the earth system and then getting the drilling system competent to manage all process risks.  Systems thinking is a team skill and using a simulator to assure all process risks are managed with certainty which begins with a two barrier assurance  process. 

The industry had this skill in the '70's but in the '80's the focus on money rather the quality has left you in a situation where there isn't a competence to assure a two barrier process.  See the Macondo blowout inquiries.  No reference to the earth system and the value of operating know there are two verified barriers at all times.  If you have a BOD for the well we can help you create an RCM based ideology for installing and maintaining the BOP
Total Posts: 2
Join Date: 17/07/18
Thank you Neil.
Drilling Supervisor
Total Posts: 59
Join Date: 11/09/10

It is not based upon the engineers decision.

The drilling contractor AND the operator will have specific requirements for the stack arrangements (including where the choke and kill lines enter the stack bore).

There should be a bridging document which specifies whose policies (contractors OR operators) will apply for the contracted work.

Both parties need to agree the stack arrangement before the rig goes on contract.


Neil Guthrie
Posted by

Thiha Htoo Naung



Total Posts: 2
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