Overpressure protection strategy for wellpads in a highly sensitive environmental location

[Sesquipedalianist]

Dear All.
A client's current preferred OPP strategy for wellpads (to flowline) is to use an instrumented PSHH based first protective layer and PSV that releases to emergency drilling pits as second layer. Because of the environmental sensitivity of the location, use of HIPPS would have been better however the client argues that the reaction response may not be sufficient enough hence the discounting for the HIPPS. My view is bladder accumulators could be used to dampen the pressure increase which would give enough time to the HIPPS to react and hence reduce on the need (if any) of the PSV.


Full rating is discounted due to high number of wellpads thus it would be costly achieving a #1500 through out the whole system!

What strategy would you propose. Do you think it is wise to go PSV for fast transient handling. Wat is your experience with use of emergency drilling pits? Any benefits or challenges faced using such pits?

(A multiphase fluid is handled O, W,G)

 

[EmmanuelTop]

Dynamic simulations are required to establish set point for a HIPPS - this is exactly due to a different nature of any system out there (different volumes, different flows, different phase fractions etc.). So, you don't want a bladder accumulator, you need a well designed HIPPS. Secondly, a bladder accumulator would significantly reduce integrity level of the HIPPS.

There is no such thing as "common sense" - Apollo RCA

 

[don1980]

I'm guessing that this HIPPS probably needs a time-delay to avoid unnecessary trips. I don't see any problem with using a 1500# bladder accumulator, but how bib would it need to be, after accounting for the HIPPS time-delay? That may render it impractical, as a stand-alone alternative to the PSV.

 

[Sesquipedalianist]

Thank you all for the responses

The decision not to use HIPPS is because its reaction time will be too slow to fast transients such as blocked outlet scenarios.


So the idea is since a bladder accumulator can dampen the pressure increase, it would give enough time for the HIPPS to react appropriately in time!



My query though is what is your view in PSV relieving into emergency drilling pits. Any experience on this routine

 

[MortenA]

its just so more complicated and possibly costly going dowwn the instrumented route (testing and sourcing of instruments valves etc) that you should try to convince your client to use fully rated piping (if its #1500) to the separator...

Best regards, Morten

 

[Sesquipedalianist]

MortenA,
Thank you for the response. Yes indeed going full rated would be a sound option however the economics may not support it (roughly over 50 well-pads). The HIPPS option may also suffer from poor reliability since the complexity of managing a high number of such systems creates an obstacle.

Cheers,
Sesq.