Page 143 - Petroleum and Gas Field Processing

3. Determine the maximum oil pad thickness, H o,max from Eq. (9)
with d m equal to 500 mm.
4. Determine D max from Eq. (12).
5. For diameters smaller than D max , determine the combinations of
D and L that satisfy the gas capacity constraint from Eq. (13),
substituting 100 mm for d m .
6. For diameters smaller than D max , determine the combinations of D
and L that satisfy the retention time constraint from Eq. (17).
7. Compare the results obtained in steps 5 and 6 and determine
whether the gas capacity or retention time (liquid capacity)
governs the separator design.
8. If the gas capacity governs the design, determine the seam-to-
seam length of the separator, L s , from
D
L s ¼ L þ ð18Þ
12
If the liquid retention time (liquid capacity) governs the design,
determine L s from
L
L s ¼ 4 ð19Þ
3
9. Recommend a reasonable diameter and length with a slenderness
ratio in the range of 3–5. In making the final selection,
considerations such as cost and availability will be important. It
should be mentioned that, in some cases, the slenderness ratio
might be different from the range of 3–5. In such cases,
especially when the slenderness ratio is larger than 5, internal
baffles should be installed to act as wave breakers in order to
stabilize the gas–liquid interface.

Example 1
Determine the diameter and seam-to-seam length of a three-phase
horizontal separator for the following operating conditions:

Oil production rate: 8000 BPD
Water production rate: 3000 BPD
Gas–oil ratio: 1000 SCF/bbl
Oil viscosity: 20 cP
Oil specific gravity: 0.89
Water specific gravity: 1.04
Gas specific gravity: 0.65
Gas compressibility: 0.89
Operating pressure: 250 psia

Operating temperature: 95 F

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.