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Produced Water Filtration in Offshore Production

13 Apr 2021

Produced Water Filtration in Offshore Production

Anyone involved in offshore oil and gas production is aware of the problem of produced water, particularly the regulations around hydrocarbons removal.

The large volumes of water produced during the process of extracting the oil or gas from the seabed have to be dealt with, and while the preferred option is re-injection of the produced water into other wells, ultimately the greater part of it has to be discharged back into the sea.

For the purposes of this discussion, we’ll be looking into the issues around the removal of hydrocarbons. No matter what the ultimate destination of the produced water is, the offshore facility has to find some way of dealing with the level of hydrocarbons it contains. More specifically, any facility operating within an area of water that covers the greater North Sea, Arctic waters, the Celtic Sea, the Bay of Biscay and Iberian coast and the wider Atlantic, will find itself having to comply with the standards put in place by OSPAR. This convention, with 15 signatory countries, is aimed at conserving this marine environment.

Intrusive and Expensive Consequences for Failure to Deliver

The relevant part of OSPAR we're examining in more detail here is around the topic of hydrocarbons in produced water for which there is a limit of 30ppm. To regulate on this, the levels in any water to be discharged into the sea are consistently monitored and tested and any facility producing levels in excess of 30ppm will find itself under intense scrutiny. Initially, this scrutiny will involve having to send samples of the produced water to onshore labs for analysis - on a daily basis.

Clearly, using a helicopter to fly samples between a facility and the mainland on a daily basis is an intrusive and expensive process that has the additional effect of impacting negatively on the carbon footprint of the facility in question. Even more damaging to business, if the level of hydrocarbons in the produced water can’t be lowered, all of the produced water being generated will need to be transported to the mainland for treatment before being returned to the sea via an overboard line.

Getting the Filtration Method Right

Of course, in an offshore environment, the most desirable solution is to clean the produced water in-situ, get the levels of hydrocarbons below 30 ppm - and then return it to the sea. This is only ‘easy’ with regard to the clear message around the desired result - get the levels below 30 ppm. However, the level of filtration required is often difficult to achieve and even more problematic when the potentially un-manned nature of an offshore facility is taken into account. Gas and oil producers have a range of obligations to meet. From the regulations governed by OSPAR and the health and safety of their own operatives to the impact of their operations on the environment.

Game-Changing

Making the right choice of produced water filtration solution that delivers the desired results consistently while simplifying and streamlining the process of meeting these obligations, can be game-changing.

Future-Proofing your Produced Water Filtration

Looking at these issues in the round, it's obvious that businesses need a trusted solution for treating produced water offshore.  SepSORB®, developed by Separo's Wastewater Treatment Services (WTS) Division, is a one-pass, plug-and-play, closed system solution that reduces the hydrocarbon content of produced water below 30ppm on a consistent basis.

two sepsorb filter units

5ppm to as Little as 1ppm

In practice, the SepSORB® option goes further than bringing the produced water below the OSPAR threshold and instead delivers filtered water which contains 5ppm and often less; sometimes dropping to as little as 1ppm which is, to all intents and purposes, clean water. This not only means that the facilities using SepSORB® are meeting their environmental obligations to the fullest possible degree it also offers full security against the very real possibility that the OSPAR threshold will drop below 30ppm in the years to come.

Plug-and-Play Filtration - Right for This Environment

There are several other produced water filtration methods in use in facilities across the world's seas. Our experience of helping many businesses address the challenges of produced water has proven that SepSORB® is superior in terms of both effectiveness and operation. The operational advantage lies in the fact that the filtration unit merely has to be installed and then switched on. Once this has been done it looks after itself until such time as the filter has to be replaced. As an example, a client in the Dutch sector previously utilised a twin system onboard requiring cartridge changeouts every second day. Following the introduction of our SepSORB® system this handling was significantly reduced with the SepSORB® filters lasting months before requiring any handling for change-outs.

close up connect sepsorb

The alternatives often require varying degrees of manual intervention – whether that means adding chemicals to break down the oil in the water or donning full hazmat gear in order to undertake the unpleasant task of cleaning out and replacing the cartridges. It's hugely problematic in the context of an offshore facility, especially one intended to be operated remotely. From ensuring the safety of personnel on the facility while carrying out these tasks to transportation costs alone there are clearly several advantages to the plug-and-play option. In terms of the operational advantages of SepSORB®, unlike alternatives that require high powered pumps to force the produced water through membranes, the system can operate at full effectiveness with a standard pump.

Complex systems are often used that require constant and homogenised fluids, the SepSORB® system is very flexible and can cope with peaks and fluctuations.

Behind this staggering result of 5ppm or less in the filtered water, is the use of a special blend of SepSORB® media which attracts and retains the hydrocarbons, allowing only the much cleaner water to pass through.

Customisable for Individual Operational Needs

In simple terms, SepSORB® is an ideal solution for produced water filtration. It's a system that can be tailored to suit the facility itself, is self-contained, requires little manual intervention for cleaning and changing filters, and delivers consistent, dependable results. It is also available in a range of sizes depending upon the capacity of the facility on which it is installed, and if needed, can be fitted with pre-filters designed to weed out the heavier solids often present in produced water.

Filtration Offshore

When the time comes for the saturated media within the system to be replaced, it can be recycled for re-use, while the "waste" material persisting on the outer shell of the original filter – having been heat-blasted and removed – can be repurposed as a recycled form of heating fuel. 

The SepSORB® vessels are easy to swap. When the valves are closed and the pressure is taken off, the vessels can be uncoupled via Camlock couplers, taken away and replaced with new ones. The new vessels can be connected via the couplers ready for use again.

In short, SepSORB® offers a chance for oil and gas production operations to avoid the kind of damaging, intrusive and expensive scrutiny which comes as a result of failing to filter hydrocarbons from produced water correctly. It not only gets the job done, but it also gets the job done simply, operating in a plug and play manner and performing remotely - without the need for manual intervention.

If you're currently dealing with daily inspections of produced water this alternative solution is worth considering. You'll be in good company. Compulsory inspections will reduce as SepSORB® begins to turn the tide on the problem, dropping to weekly and then monthly intervals - leaving your operation to get on with the job in hand – much like SepSORB® itself.     

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