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The reeds themselves form a wetland covering around 2.4 million square metres of previously arid desert. They are irrigated by water that is a by-product of oil production activities in Nimr carried out by Petroleum Development Oman (PDO), in which Shell holds a 34% interest. The field has long been characterised by the high percentage of water that also comes to the surface with the oil.

Since 2011, a sizeable proportion of Nimr’s produced water – some 100,000 cubic metres of it per day – has been flowing into a special treatment plant operated on PDO’s behalf by the environmental services company Bauer Nimr. The facility incorporates a clever settling tank and centrifuge systems that removes any residual traces of oil (which are reclaimed) before the water flows into the beds to be cleaned by micro-organisms that live among the roots of the reeds as well as by algae.

Because the whole facility is constructed on a man-made slope, the water requires no pumping or other mechanical stimulus to flow through it, making the plant both highly energy-efficient and extremely reliable.

Thanks to this unique, natural process the water taken from the beds is pure enough to be used for drilling new wells, which saves pumping clean water from shallow aquifers. PDO also draws on it to help make up the polymer mixtures used in its chemical EOR (enhanced oil recovery) project in Mamul, and it can be used for hydraulic fracking, which is a process by which high pressure water injection is deployed to fracture reservoir rock in order to improve its permeability.

Outside of out oilfield operations, PDO is investigating the potential of ear-marking some of the water to irrigate crops that are tolerant to high levels of dissolved salt – so-called biosaline agriculture. After all these practical usages have taken their share, any remaining water is passed into giant evaporation ponds to let nature take its course, after which PDO plans to harvest the salt deposits left behind.

Since the Nimr reed beds opened, PDO has been able to shut down five of the 12 high pressure pumps that it uses to dispose produced water from the field into deep-lying aquifers (ensuring it is kept well away from drinking water supplies). PDO estimates that the energy we’ll save as a result could add up to the equivalent of around 23 billion cubic feet of gas over a 10 year period. 

The reed bed project has generated a huge amount of interest both within the oil and gas sector and wider environmental community. Among the many international awards given to the project, has been the prestigious Global Water Award, which was presented in 2011 by former United Nations Secretary-General Kofi Annan.

Oil-eating microbes

Oil produced at Nimr in Oman reaches the surface mixed with 90% water, which traditionally must be cleaned before being pumped back beneath the ground

Oil produced at Nimr in Oman reaches the surface mixed with 90% water, which traditionally must be cleaned before being pumped back beneath the ground