Page 203 - Petroleum and Gas Field Processing

REVIEW QUESTIONS AND EXERCISE PROBLEMS

1. Crude oil needs to be desalted for the following two main reasons:
(a)
(b)
2. Crude oil should be desalted if its salt content exceeds
PBT.
3. Define the following terms:
(i) Remnant water:
(ii) Dilution water:
(iii) BS&W:

4. What is the main advantage of a two-stage desalting process over a
single-stage desalting process?
5. Explain why desalting takes place after and not during the
dehydration (emulsion treatment) process.
6. Sketch and briefly describe a two-stage desalting process.
7. An oil field produces 200,000 bbl/day of net oil with a salt content of
10 PTB. The oil out of the emulsion treater contains 0.3% water
(salinity ¼ 250,000 ppm and specific gravity ¼ 1.07). In the desalting–
dehydration process, the oil is mixed with dilution water (3000 ppm
salinity and 1.02 specific gravity) and dehydrated down to 0.1%
BS&W. Assuming that the mixing efficiency is 80%, determine the
following:
(a) The salt content in PTB of the oil out of the emulsion treater
(b) The amount of dilution water required (in bbl/day)
(c) The amount of disposed water (in bbl/day) and its salinity (in
ppm)
8. A dehydration–desalting system consists of the following:
(a) A first-stage dehydration only (no wash water added) which
receives the fed containing 10% by volume water having a
salinity of 250,000 ppm and a specific gravity of 1.06. The
dehydration is carried out to produce oil with 0.3% water.
(b) A second-stage desalting, which receives the effluent of the first
stage and mix it with 10% by volume of wash water containing
3000 ppm salt. Then, dehydration is carried out to produce oil
with 0.2% BS&W.
Determine the salt content in PTB of the following:
(i) The oil entering the first stage

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