Page 204 - Petroleum and Gas Field Processing

(ii) The oil leaving the first stage
(iii) The oil leaving the second stage
9. A two-stage desalting unit is used to treat 100,000 BPD of net oil. The
oil entering the first stage contains 3% water having 280,000 ppm salt
and 1.07 specific gravity. The oil is mixed with recycled water from the
second stage (mixing efficiency ¼ 80%) and dehydrated down to 1%
water content. In the second stage, the oil is mixed with 7000 bbl of
water having 3000 ppm salt and a specific gravity of 1.02 (mixing
efficiency ¼ 80%) and is then dehydrated down to 0.1% water content
and salt content of 10 PTB.
(a) Draw a flow diagram of the described process.
(b) Determine the salinity [in lb of salt/bbl of water (lb s /bbl w )] at all
points.
(c) Determine the salt content of the oil (in PTB) at all points.
(d) Determine the amounts or recycled water and disposed water for
the two stages.
(e) If only a one-stage desalting unit was used, determine the amount
of dilution water needed to produce the same final oil quality as
for the two-stage unit.

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