Page 246 - Petroleum and Gas Field Processing

shutdown signal measured before the oil in the pile comes within 10 ft of
the bottom.
Disposal piles are used to collect treated produced water, deck
drains, treated sand, and liquids from drip pans and dispose of them deep
below the surface. Disposal piles are also useful as traps for oil in the
event of equipment failure or upset operating conditions. The deck
drainage, normally rainwater and washdown water, is saturated with
oxygen and may contain sand and other solids. Therefore, it should not be
treated in the same equipment as produced water to avoid corrosion and
plugging problems. Disposal piles are particularly useful for disposal of
the platform drainage.

Skim Piles
The skim pile is basically a disposal pile equipped with a series of inclined
baffle plates and oil collection risers, as shown in Figure 9. The presence
of these baffles plates serves two functions. It reduces the distance a given
oil droplet has to rise to be separated from the water and creates zones of
no flow below each plate. The oil droplets rise to the zone of no flow
between two successive plates, where coalescence and gravity separation
occurs. The coalesced large oil droplets travel up the bottom side of the
plate and into the oil collection riser to the surface of the pile where oil
could be skimmed out.
Skim piles have two specific advantages over standard disposal piles.
Skim piles are more efficient in separating oil from water. Skim piles also
provide for some degree of cleaning sand that may be present in the water
from oil.

SP Piles
In this type of device, the disposal pile is equipped with a number of
equally separated SP packs and oil risers. As water flows through a SP
pack, coalescence of oil droplets occurs due to the induced turbulence. As
the water travels out of the SP pack to the next SP pack, the larger oil
droplets rise to form an oil pad below the upper SP pack. This continues
as the water goes from one SP pack to the next. The oil accumulated
below the bottom SP pack rises to the oil pad above through the risers
until it reaches the surface to be pumped out.
The SP packs are normally designed to develop oil droplets to a
maximum size of 750 mm. The number of SP packs needed is determined

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