Page 180 - Petroleum and Gas Field Processing

such cases, however, the design (following steps) may be executed
for different assumed treating temperature and a final decision is
made based on analysis of the design results.
2. Determine the diameter of the water droplet that must be
removed [from Eq. (10) or (11)].
3. Use Eq. (13) to obtain the relation between D and L that
satisfies the settling constraint. Assume various values of D and
determine the corresponding values of L from this relation.
4. Use Eq. (14) to obtain another relation between D and L that
satisfies the retention time constraint. For the same values of D
assumed in step 3, determine corresponding values of L from this
relation.
5. Compare the results obtained from the above two steps and
select a combination of D and L that satisfies both settling and
retention time constraints.
6. Use Eq. (9) to determine the heat requirement for the selected
treating temperature.

Example 1
Determine the heat requirement and the size of the settling/coalescing
section of a horizontal heater treater for the following conditions:

Oil flow rate: 7000 BPD
Inlet B.S.&W.: 15%
Outlet B.S.&W.: 1%
Oil specific gravity: 0.86

Oil viscosity: 45 cP at 85 F

20 cP at 105 F

10 cP at 125 F
Water specific gravity: 1.06

Specific heat of oil: 0.5 Btu/lb F
Specific heat of water: 1.1 Btu/lb F

Inlet temperature: 85 F
Retention time: 20 min

Treating temperature: Examine 105 F, 125 F, and no heating
Solution
Use Eq. (10) to determine the water droplet diameter for each treating
temperature:
For T ¼ 1258F: d m ¼ 200 o ¼ 200ð10Þ 0:25 ¼ 356 mm

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