Page 183 - Petroleum and Gas Field Processing

of the treated oil until he determines the optimum operating conditions that
provide the required treatment with minimum heating. Optimization of the
operating conditions is an important activity and should be conducted as
often as possible to adopt with changing field conditions.

5.8.2 Sizing Vertical Treaters
Water Droplets Settling Constraint
Similar to the analysis performed for the horizontal treater, we shall start
with the settling equation, [Eq. (3)]:
ð
Þd m ft
6
u ¼ 1:787 10 ð3Þ
o s
This equation gives the terminal settling velocity of the water droplet. For
settling to occur, the upward average velocity of the oil must not exceed
the water settling velocity. The average oil velocity, u 0 , is obtained by
dividing the oil volumetric flow rate, Q o , by the flow cross-sectional area,
2
A, which is the cross-sectional area of the theater: A ¼ (p/4)(D/12) .
Therefore,
3 5
Q ðbbl=dayÞ 5:61ðft =bblÞ 1:1574 10 ðday=sÞ
o
u o ¼
2
ð =4ÞðD=12Þ
Q o ft
2
u o ¼ 1:19 10 ð15Þ
D 2 s
Applying equation u o [Eq. (15)] to u [Eq. (3)], we obtain
2
D ¼ 6665 Q o o 2 in:ft ð16Þ
ð
Þd m
Retention Time Constraint
The reaction time, t, can be obtained by dividing the volume of the
settling/coalescing section occupied by oil, V o , by the oil volumetric flow
rate, Q o . Let H be the height of the coalescing/settling section (in in.);
then,
2
ð D =4 144ÞðH=12Þ
t ¼ 4 min:
5:61Q o 6:944 10 ðday=minÞ
2
Solving for D L, we get
2
2
D H ¼ 8:575Q o t in: ft ð17Þ

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