Fate and transport of nanohybrids in subsurface media for oil field applications

Interfacially active carbon nanotube hybrids have potential to be used in reservoir development applications. Carbon nanotubes hybrids (CNT) can act as carriers for catalytic nanoparticles into regions far inside the reservoir; they have the ability to stabilize water/oil interface in emulsions or can be used as contrast agents or sensors. One of the main challenges for successful utilization of these nanoparticles is the difficulty associated with stabilizing their dispersions and propagating them through the wellbore rock or deep inside the reservoir in harsh reservoir conditions of salinity and temperature. In this work, CNT were dispersed in high salinity brine using a combination of two polymers Gum Arabic (GA) and hydroxyethyl cellulose (HEC-10) and were propagated through porous media with minimum retention. It was found that GA is able to debundle the nanotubes into individual ones by adsorbing on the surface of nanotube while HEC-10 is thought to generate steric repulsion that keeps the tubes well dispersed and prevent them from agglomeration in the presence of high salt concentration. The combination of these two dispersing polymers was found crucial for successful propagation of nanohybrids through consolidated or unconsolidated porous media. Stable CNT dispersions have been propagated with low retention through 6” Berea cores of permeabilities as low as 200mD in 10% brine (8% NaCl and 2% CaCl2) and a temperature of 65oC. Carbon nanotube adsorption inside the core was found to be ranging between 0.02 and 0.04mg per gram of dry core weight and the overall nanotubes cumulative recovery was more than 80% of the injected nanoparticles with a normalized CNT concentration approaching 97% of the injected concentration. Increased retention of nanohybrids in the presence of oil in an oil pretreated core in comparison to an oil-free core has been observed which suggests adsorption of nanohybrids to the oil/water interface inside the core. The demonstration of the successful propagation of CNT through Berea cores is an important first step in the process of incorporating them into advancing reservoir characterization and/or enhanced oil recovery technologies