Stabilization of nickel nanoparticle suspensions with the aid of polymer and surfactant: static bottle tests and dynamic micromodel flow tests

Nickel nanoparticles can work as catalyst for the aquathermolysis reactions between water and heavy oil. A homogeneous and stable suspension is needed to carry the nickel nanoparticles into deeper reservoirs. This study conducts a detailed investigation on how to achieve stabilized nickel nanoparticle suspensions with the use of surfactant and polymer. To stabilize the nickel nanoparticle suspension, three surfactants including sodium dodecyl sulfate, cationic surfactant cetyltrimethylammonium bromide and polyoxyalkalene amine derivative (Hypermer) along with xanthan gum polymer were introduced into the nickel nanoparticle suspension. Static stability tests and zeta potential measurements were conducted to determine the polymer/surfactant recipes yielding the most stable nickel nanoparticle suspensions. Dynamic micromodel flow tests were also conducted on three suspensions to reveal how the nickel nanoparticles would travel and distribute in porous media. Test results showed that when the injection was initiated, most nickel nanoparticles were able to pass through the gaps between the sand grains and produced in the outlet of the micromodel; only a small number of the nickel nanoparticles were attached to the grain surface. A higher nickel concentration in the suspension may lead to agglomeration of nickel nanoparticles in porous media, while a lower concentration can mitigate this agglomeration. Moreover, clusters tended to form when the nickel nanoparticle suspension carried an electrical charge opposite to that of the porous media. Follow-up waterflood was initiated after the nanofluid injection. It was found that the waterflood could not flush away the nanoparticles that were remaining in the micromodel.