Nano-sand in EOR

Article by Neil Clark

MORE oil could be recovered from wells by injecting a mixture of ‘nano-sand’ and a surfactant, according to researchers in Wales and Iran.

Globally, an average of only 40% of an oilfield’s total resource is recovered. The importance of maximising yield from existing wells rather than seeking new production has been recently recognised, leading to the development of enhanced oil recovery (EOR) techniques. This is often achieved by pumping substances into a well, including hot water and chemical agents such as surfactants. Effective EOR requires reducing the capillary pressure that slows oil droplets moving through a reservoir.

Now, collaborative work from Swansea University in the UK and Islamic Azad University in Iran, has demonstrated potential yields of 58% by injecting complexes made from sodium dodecyl sulfate (SDS) surfactant and fumed-silica nanoparticles (Si-NP).

The researchers used plates of etched glass to create a 5-spot glass micromodel to evaluate suitable EOR oil displacement agents. The model’s pores were saturated with oil and then SDS and SDS/Si-NP solutions injected. Similar micromodel experiments are often used to investigate the mechanism of fluid flow on porous mediums via flow visualisation, pore space geometry, topology and heterogeneity effects.

Their results showed an oil recovery of 45% when adding SDS alone; this then increased by 13% with the addition of Si-NP.

Lead researcher Andrew Barron said: “It is a surprise that the addition of silica nanoparticles, essentially nano-sand, to the surfactant solution leads to such a large flow modification.

“The particles seem to reduce the viscosity of the oil as well as changing the way it interacts with water, both of which contribute to improve the amount of oil that is swept towards the recovery point.”

In the paper, the authors suggest that the increased performance and change in oil displacement mechanism could possibly outweigh upfront cost issues of nanoparticles.

Regarding scaling up the process, Barron said: “We believe that it does allow for a scalable process, maybe not with these exact nanoparticles, but the concept shows great promise – we are hoping to do a larger test soon before looking at a pilot scale process.”

Industrial and Engineering Chemistry Research:

Article by Neil Clark

Staff Reporter, The Chemical Engineer

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