Heavy crude oil has lower solubility and higher density than that of light crude oil, and it mostly comes in the form of natural bitumen from oil sand. Therefore, there are significant challenges in both the production and transportation of heavy oil. Oil-in-water emulsions are commonly used to reduce the viscosity, but subsequent demulsification can be challenging. Here, we investigate pH-responsive polymer coated nanoparticles (PNPs) that are interfacially active and can be used to either stabilize or break oil/water emulsions by varying pH. Silica particles with dimethyl ethyl acrylamide (DMAEMA) chains covalently grafted to the surface are prepared though a reversible addition fragmentation chain transfer (RAFT) grafting-through technique. TGA, DLS, and TEM are used to confirm the attachment of the polymer coating, and the resulting polymer-coated nanoparticles contain 60 wt % polymer. We show that DMAEMA PNPs can be used to stabilize emulsions of high viscosity Venezuela heavy oil at additive concentration as low as 0.1 wt % and at a neutral pH. The performance of the PNPs exceeds that of pure DMAEMA homopolymer additive or of just water with no additive, and approximately 10mg crude oil is stabilized for each 10 mg of PNP used. By changing the pH of the aqueous solution, the interfacial activity of the DMAEMA decreases, and the emulsion is destabilized. Surface energy measurements show a 20 degree difference in contact angle on a crude oil coated substrate for a DMAEMA PNP drop at pH=7 and pH=2. Finally, we perform sandpack flooding using PNPs as additives to mobilize heavy oil. The PNPs penetrate the sandpack and are able to recover more than 25 wt % of the crude oil in place. This work demonstrates the applicability of polymer-coated nanoparticles as surface active materials for EOR processes and for heavy oil transportation.

pH-responsive polymer coated nanoparticles for controlled emulsification of heavy oil

253rd National Meeting (2017)

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