Page 34 - March 2020 - WT Site

Comparison of Advanced Water Technologies

This article will discuss some common definitions of water quality parameters, such as oil concentration,
emulsions, free oil, etc.
By Chip Westaby

Challenges Comparing Advanced Water Depending on the water salinity produced in an oil well and
Treatment Technologies the destination of the water, the required discharge quality can
vary significantly. Most treated produced water is injected into a
Produced water treatment systems are becoming more formation for disposal. Some treated produced water is injected
sophisticated and complex with the addition of tertiary treatment into the oil formation to increase oil production, while most is
systems, sometimes referred to as polishing systems. Additionally, injected into a separate formation for permanent disposal. In
produced water chemistry, process design and discharge some offshore operations, the produced water can be discharged
requirements are different from location to location. The to the surface.
advanced treatment systems can be needed when produced water
is being reused or recycled and when produced water volume has In only a few locations, the highly treated produced water
increased beyond the treatment system’s capacity. The process can be discharged to a fresh water source or recycled. In arid
variability makes the technologies used in these treatment systems environments where the demand for water sources is high and
diverse, such as reverse osmosis membrane systems, absorbent with advanced water treatment, the produced water can be used
media and cleanable ceramic membranes. as fracking water source, or irrigation. To meet the increased
water quality requirements, water treatment companies have
With the variable process conditions, the specialized treatment developed advanced water treatment systems. However, water
systems’ performance parameters can differ greatly between quality requirements for reinjection are more lenient than for
products with similar technologies. Likewise, some common offshore discharge or recycling.
performance parameters lack universal definition, making
comparisons between two systems difficult. For instance, there Water treatment systems can be efficiently designed for the
are many different methods to measure oil in water concentration, process and discharge conditions expected during the initial
each with a different definition of what is considered oil. This phase of production and in many cases designed to accommodate
paper will review the technology and performance parameters expected production changes for the future. For instance, an
of three tertiary water treatment technologies and some of their oil well may have 10-20 per cent water during the first year of
typical applications. operation. However, the projected life of the well calls for adding
injecting water into the oil formation to enhance the production
Produced Water Discharge Requirements after five years of operation. This is referred to as water flood
where the water concentration can increase up to 75–90 per cent.
There are no consistent global water conditions in oil fields due With the expected change in produced water volumes, the original
to the significant variability in reservoirs, production techniques water treatment system can be designed to treat the higher water
and water discharge methods. Water can be up to 99% of the volumes and achieve discharge quality standards.
total liquids produced in some places, while other fields may not
produce any water. Water salinities and mineral content can also Water treatment systems are challenged when the production style
vary from fresh to almost saturate brines. change, the water quality needs change or there is insufficient room

36 Water Today - The Magazine March 2020