This topic will demonstrate you how to determine accumulator bottles required for Koomey Unit (Accumulator Unit) in order to close the surface BOP stack.
This is a specification of Accumulator (Koomey) Unit.
Accumulator 3,000 psi system
Volume each bottle is 10 gallon.
Pre charge pressure is 1,000 psi.
Minimum operating pressure is 1,200 psi (200 psi over pre charge pressure)
Usable fluid per gallon is 5 gallon.
Safety factor require is 50 %. This safety factor may be different depending on each company’s requirement.
BOP Stack and HCR’s as listed below:
| Equipment | Gallon to open | Gallon to close |
| Annular Preventor | 4.0 | 4.5 |
| Upper Pipe Rams | 3.0 | 3.5 |
| Blind Shear Rams | 3.5 | 4.0 |
| Lower Pipe Rams | 3.0 | 3.5 |
| Choke HCR | 0.5 | 0.5 |
| Kill HCR | 0.5 | 0.5 |
Please follow the steps below for calculation
1. Determine total volume require to close all of equipment
Volume = 4.5+3.5+4+3.5+0.5+0.5 = 16.5 gallon
2. Volume accounted for safety factor
Volume = 16.5 x 1.5 = 24.75 gallon
3. Determine numbers of accumulator bottles required to meet volume determined in step#2
Number of bottles = volume ÷ usable fluid per bottle
Number of bottles =24.75 ÷ 5 = 4.95 so you round it up to 5 bottles
In order to close all BOP as per requirement without any assistance of electric and pneumatic pumps, you need to have a total of 5 accumulator bottles.
You will see that based on the calculation above, determining required Koomey bottles is quite straight forward. Thing to remember is that you must use closing volume not opening volume. I see many people using the wrong figures. Even though it may not have big impact on the final result, you need to select the right figures for calculation. Moreover, the safety factor may be different based on the regulations of your working area or your company policy.
References
Cormack, D. (2007). An introduction to well control calculations for drilling operations. 1st ed. Texas: Springer.
Crumpton, H. (2010). Well Control for Completions and Interventions. 1st ed. Texas: Gulf Publishing.
Grace, R. (2003). Blowout and well control handbook [recurso electrónico]. 1st ed. Paises Bajos: Gulf Professional Pub.
Grace, R. and Cudd, B. (1994). Advanced blowout & well control. 1st ed. Houston: Gulf Publishing Company.
how could the Safety factor require is 50 % converted to 1.5 ??
You need to have 50% (equal to 0.5) more. Therefore you need to have a total of 150% which is equal to 1.5.
I need safety information on Koomey Unit, mud pumps, well control. in short Safety information on HSE drilling operations
Thanks for this info. Honestly, I just learnt this today.
What size of BOPs are we using for this calculation ?
BOP size depends on what you need to fit with your operation.