FILTRATION & SEPARATION
DEALING WITH PRODUCED WATER EFFECTIVELY I
t’s no secret that drilling for oil and gas is dirty work, but people outside the industry often overlook the challenges associated
with the proper treatment and disposal of produced water. Sometimes called flowback or formation
water, produced water is a brackish or saline solution that’s brought to the surface during the drilling and production process. It’s frequently contaminated with substances that are hard to remove in situ, including dispersed oil, dissolved gasses, heavy metals and suspended particles of clay and wax, drilling chemicals, bacteria and dissolved hydrocarbons. Strict environmental regulations govern
the discharge of produced water. In the North-East Atlantic and the North Sea, the OSPAR convention demands that levels of oil in water be brought down below 30mg/l before produced water can be dumped back into the sea. The EU’s Water Framework Directive (WFD)
is committed to eventually guaranteeing 0mg/l of oil in water discharged in its waters, which will have many blue-chip oil and gas companies scrambling to purify the produced water generated by their drilling operations. But treating produced water can be
costly and time consuming. Approximately 22-25% of the UK’s output is reinjected into underground wells, but the rest is normally treated with oxidising chemicals that are supposed to break down contaminants, or subjected to inefficient MED (distillation) processes that see saline produced water subjected to high heat; evaporated and then recovered as pure water. Some operations also pay to transfer their
produced water to onshore treatment facilities, but water’s heavy and therefore expensive to transport, and the dissolved hydrocarbon content of produced water makes moving it a challenging prospect. Luckily, there is another - better - way to
treat produced water. Recent advances in micro and ultrafiltration technology mean that it is possible to build systems that can filter out the oil and unwanted contaminants found in produced water. Separo (formerly Solids Control Services)
have been working on a plug and play system that can take the oil in water content of produced water from 100 or more to below 30ppm (parts per million) in a single pass, which is more than enough to satisfy all regulatory requirements. And using a combination of filter media
means that they can also remove a lot of the heavy metals and inorganic compounds that foul the produced water generated by the oil and gas industry. Andrew Crutchley – Separo’s chief
operating officer, said that these innovative 20 SEPTEMBER 2021 | PROCESS & CONTROL
Filter units from Separo reduce the contaminants in produced water to satisfy industry regulations
new filter units are making a significant difference to a number of rigs and platforms currently operating in the North Sea. “The filter vessels are small” he said, “some of them as small as 1.2m3
and the average
installation takes up less than 15 square feet in total, which is very important on any offshore installation, where space is tight and every inch of deck space has to be accounted for. But they can still handle large volumes of water. “Most units can handle 12-20 cubic metres per
Fig.1: A table showing the chemical composition of produced water from a typical oil field
hour, depending on the size,” he continued. ”Then there's always the option to link them up in sequence too, enabling you to purify the large volumes of produced water generated by older wells.” “It’s a scalable technology that can be easily
delivered via a supply vessel and set up in a matter of hours, and it’s relatively green too. Water can be discharged at source – without the need to transport it to onshore facilities for cleaning – and the media itself can be returned back to shore and reactivated to cut down on the amount of waste produced.” As oil and gas wells in the North Sea continue
to age and the amount of produced water climbs, innovative filtration technologies like this could be key to maintaining legislative compliance at a reasonable cost. Sources:
https://academic.oup.com/ijlct/article/ 9/3/157/807670
https://www.ospar.org/documents?v=6945 https://www.sciencedirect.com/science/article/ abs/pii/S030438940900778X
https://www.miljodirektoratet.no/globalassets/p ublikasjoner/m1370/m1370.pdf
https://pubmed.ncbi.nlm.nih.gov/24119441/
Separo
www.separo.com
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