EFFECT OF THE MAGNETIC IRON CORE-CARBON SHELL NANOPARTICLES IN CHEMICAL ENHANCED OIL RECOVERY FOR ULTRA LOW INTERFACIAL TENSION REGION

Resumen

Some of advantages of the simultaneous use of surfactants and nanoparticles in EOR processes are  the  increase  in  the  efficiency  of  injection  fluid  for  sweeping,  the  reduction  of  the  adsorption  of  surfactant  onto  reservoir  rock,  the  alteration  of  wettability  and  the  reduction  of  water/crude  oil  interfacial tension. However, a large amount of nanoparticles required in chemical enhanced oil recovery (CEOR) processes might limit their application. Therefore, the main objective of this work is to synthesize, characterize and evaluate magnetic iron core-carbon shell nanoparticles that can be recovered and its impact on the reduction of surfactant adsorption on the porous media, and oil recovery  at  reservoir  conditions.  The  additional  benefit  of  the  proposed  method  is  that  these  nanoparticles can be recovered and re-used after the application due to its magnetic properties. The magnetic iron core-carbon shell nanoparticles were obtained following a new one-pot hydrothermal procedure  and  were  carbonized  at  900  °C  using  a  teflon-lined  autoclave.  The  core-shell nanoparticles  were  characterized  using  scanning  electron  microscopy  (SEM),  dynamic  light  scattering  (DLS),  N₂  physisorption  at  -196  °C,  X-ray  diffraction  (XRD),  X-ray  photoelectron  spectroscopy (XPS) and magnetometry measurements. Magnetic iron core-carbon shell nanoparticles with an average particle size of 60 nm were obtained. The XPS spectrum corroborated that magnetic Fe  (0)  of  the  core  was adequately  coated  with  a  carbon  shell.  The  interfacial  tension  (IFT)  was  measured  using  a  spinning  drop  tensiometer  for  a  medium  viscosity  crude  oil  and  a  surfactant  mixture.  The  minimum  IFT  reached  was  approximately  1×10-⁴  mN  m-¹  at  a  nanoparticles  concentration of 100 mg L-¹. At this concentration, the dynamic adsorption tests demonstrated that the  nanoparticles  reduce  33%  the  adsorption  of  the  surfactant  mixture  in  the  porous  media.  The simultaneous  effect  of  core-shell  nanoparticles  and  the  surfactant  mixture  was  evaluated  in  a  displacement test at reservoir conditions obtaining a final oil recovery of 98%.