Page 35 - March 2020 - WT Site

to add the system. In some offshore facilities, new oil production treatment technologies and methods of measuring the
formations that add total liquid volume can be developed and fed performance must be connected to this discussion.
into the same treatment system. The new field may not have been
considered when designing the water treatment system. Organoclay

Offshore facilities are limited by the space and weight constraints
of the platform. They need small and lightweight solutions.
Onshore facilities, on the other hand, can usually add more
treatment tanks. If the production method is changed from the
water flood to a different recovery method like steam, surfactant,
or CO2 floods, the water treatment system may also need to
change. The production technologies used in the secondary
recovery method may not have been developed or considered
when the original water treatment system was designed, and the
system isn’t designed to treat the new production method.

Tertiary Treatment Systems/Polishing Filters
Storage tanks and pressurized vessels for oil, water and gas
separation are considered the primary treatment systems. They Xedia Process Solutions has developed an organoclay-based
usually have some internal structures and no moving parts. Most technology which can remove oil droplets and some dissolved
onshore facilities with plenty of space are well suited with this oil from produced water processes and back washed in some
treatment. When liquid volumes grow, tanks can be added to cases. This technology can be retrofitted to some existing water
improve treatment. When space is not available, or when higher treatment systems without adding new vessels. This technology
water quality is needed, a secondary treatment system can be is capable of reducing the free oil concentration from 100 ppm,
added. Secondary treatment systems can include enhanced gravity typically seen after primary separation tanks, to less than 1 ppm
systems and gas flotation systems. Gas bubbles added to the water and remove solids at the same time.
will remove oil as they float to the surface. Induced gas flotation
and dissolved gas flotation are the common technologies used. Oil and solid removal filters are added as the last stage of a water
When centrifugal forces in a hydrocyclone or centrifuge are added treatment system when the water is reused or discharged to the
to the system to enhance the gravity separation, oil is removed ocean. A traditional filter media can be consumed quickly when
much faster than under normal gravity systems. water volumes increase, polymers are added or high solids are
present during upset conditions. However, with the higher loading
When the primary or secondary treatment systems are no longer capacity of the Xedia media, oil producers are able to achieve
sufficient to meet the water quality needs, frequent oil slugs and their needed water quality without adding new filter vessels. When
discharge upsets can occur. To reduce these issues, a tertiary the media is back washed, operating costs are reduced because the
system can be added to the process. These systems can include media does not need to be replaced as frequently.
absorbent media or coalescing media. Granular activated carbon
is a common and successful treatment media, but the carbon has Synthetic Walnut Shell
a high operating cost because it is consumed when removing oil
from the water. To reduce operating costs, the ideal media can be Walnut Shell Filters are a common treatment technology to
regenerated in the field without needing to be replaced often or remove free oil to low concentrations. Oil will adsorb (stick to
only used when upsets occur. the outside) to the nut shells, but not be absorbed (permanently
stick to the internals). Because the nut shells are resilient, they can
Due to the many different process conditions in oil fields and be back washed vigorously and returned to the treatment process
different water quality standards to be met, the many different with little damage or need to be refilled.

Water Today - The Magazine l March 2020 37