Oil and water tend to separate, but they mix well enough to form stable oil-in-water emulsions in produced water from oil reservoirs to become a problem. Rice University scientists have developed a nanoparticle-based solution that reliably removes more than 99 percent of the emulsified oil that remains after other processing is done.
The Rice lab engineers made a magnetic nanoparticle compound that efficiently separates crude oil droplets from produced water that have proven difficult to remove with current methods.
Produced water comes from production wells along with oil. It often includes chemicals and surfactants pumped into a reservoir to push oil to the surface from tiny pores or cracks, either natural or fractured, deep underground. Under pressure and the presence of soapy surfactants, some of the oil and water form stable emulsions that cling together all the way back to the surface.
The researchers added amines to magnetic iron nanoparticles. Amines carry a positive charge that helps the nanoparticles find negatively charged oil droplets. Once they do, the nanoparticles bind the oil. Magnets are then able to pull the droplets and nanoparticles out of the solution.
It’s often hard to design nanoparticles that don’t simply aggregate in the high salinities that are typically found in reservoir fluids, but these are quite stable in the produced water. The enhanced nanoparticles were tested on emulsions made in the lab with model oil as well as crude oil.
In both cases, researchers inserted nanoparticles into the emulsions, which they simply shook by hand and machine to break the oil-water bonds and create oil-nanoparticle bonds within minutes. Some of the oil floated to the top, while placing the test tube on a magnet pulled the infused nanotubes to the bottom, leaving clear water in between. The nanoparticles can be washed with a solvent and reused while the oil can be recovered.
News Source: http://news.rice.edu/2018/08/15/particles-pull-last-drops-of-oil-from-well-water/
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