BOP Accumulator Sizing

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56 rows x 4 columns

A B C D E F G H I J K L M N O
1 BOP Accumulator Sizing
2 Blue cells on yellow are inputs. The function volumes are EXAMPLE values: take yours from the BOP manufacturer's data.
3
4 Accumulator Bottles
5 Bottle nitrogen volume (an 11 gal bottle holds 10) 10 gal
6 Nitrogen precharge pressure 1000 psi
7 Minimum operating pressure 1200 psi
8 Accumulator operating pressure (fully charged) 3000 psi
9 Bottles installed 16 bottles
10 Design factor on the required volume 1.5 —
11
12 BOP Functions
13 Function Volume each (gal) Count Total (gal)
14 Annular preventer (close) 17.1 1 17.1
15 Pipe rams (close) 5.8 2 11.6
16 Blind/shear rams (close) 6.2 1 6.2
17 HCR valves (open) 0.5 2 1.0
18 Fluid to operate every function once 35.9
19
20 Sizing
21 Usable fluid per bottle 5.00 gal
22 Fluid required (functions × design factor) 53.85 gal
23 Bottles required 11 bottles
24 Usable fluid installed 80.0 gal
25 Pressure after operating every function once, pumps off 1,793 psi
26 Bottle count check OK: enough bottles installed
27 Remaining pressure check OK: above the minimum operating pressure
28 Precharge check OK: minimum operating pressure 200 psi or more above precharge
29
30 Accumulator Pressure as Fluid Is Drawn (all bottles, pumps off)
31 Fluid drawn (gal) Pressure (psi) Minimum operating (psi)
32 0.0 3,000 1,200
33 5.3 2,727 1,200
34 10.7 2,500 1,200
35 16.0 2,308 1,200
36 21.3 2,143 1,200
37 26.7 2,000 1,200
38 32.0 1,875 1,200
39 37.3 1,765 1,200
40 42.7 1,667 1,200
41 48.0 1,579 1,200
42 53.3 1,500 1,200
43 58.7 1,429 1,200
44 64.0 1,364 1,200
45 69.3 1,304 1,200
46 74.7 1,250 1,200
47 80.0 1,200 1,200
48 85.3 1,154 1,200
49 90.7 1,111 1,200
50 96.0 1,071 1,200
51 101.3 1,034 1,200
52 106.7 1,000 1,200
53
54 Fluid required (gal) Pressure (psi)
55 53.85 0
56 53.85 3000
Accumulator pressure against fluid drawn 0 1,000 2,000 3,000 Pressure (psi) 0 20 40 60 80 100 120 Fluid drawn (gal)
Accumulator pressure Minimum operating pressure Fluid required

Description

Sizes a BOP accumulator unit. Enter the bottle size, the precharge, the minimum and fully charged operating pressures, the bottles installed and a design factor, and list the fluid each BOP function takes. The sheet returns the usable fluid per bottle, the fluid required, the number of bottles that needs and the pressure left after operating every function once with the pumps off. Checks cover the bottle count, the remaining pressure and the precharge margin. A chart shows accumulator pressure against the fluid drawn, with the minimum operating pressure and the required volume marked.

Parameters:

  • Bottle volume: Nitrogen volume per bottle (gal). An 11 gal bottle holds 10 gal.
  • Precharge, minimum and operating pressure: Nitrogen precharge, the lowest pressure the system may fall to, and the fully charged pressure (psi)
  • Bottles installed, design factor: Count and the factor applied to the functions' volume (dimensionless)
  • BOP functions: Fluid to operate each function (gal) and how many there are. The shipped values are examples; use the BOP manufacturer's data.

Method: The precharge nitrogen follows Boyle's law, so a bottle charged to P_max gives up V × P_pre × (1/P_min − 1/P_max) of fluid by the time it falls to P_min. Fluid required = the functions' total × the design factor. Bottles required = required / usable per bottle, rounded up. After V_d of fluid is drawn from each bottle, the pressure is V × P_pre / (V × P_pre / P_max + V_d), which gives the drawdown curve and the pressure left after one sequence. A design factor of 1.5 on the close volume is a common rule of thumb; API Standard 53 and API 16D set the requirement for a specific rig, and this sheet does not replace them. The formulas are the sheet's own _PO.DE.* LAMBDAs, so it calculates with no add-in installed.

Example: 10 gal bottles precharged to 1,000 psi and worked between 3,000 and 1,200 psi give 5.0 gal each. The example stack takes 35.9 gal, or 53.85 gal with a 1.5 design factor, so 11 bottles. The 16 installed hold 80 gal usable and are left at about 1,790 psi after operating every function once.

How to use this blueprint
  1. In Excel, go to the Petroleum Office ribbon tab and click Blueprint Manager
  2. Search for BOP Accumulator Sizing
  3. Click on the blueprint to preview
  4. Click Insert to place it into your worksheet. Modify the input values to match your data.
Tags:
drillingwell-controlBOPaccumulatorkoomeyprechargeboyles-lawsizing

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