Characterisation and application of charcoal-based nanofluids in enhanced oil recovery (EOR)

This study investigates charcoal-based nanofluids for enhanced oil recovery (EOR), as a new route of carbon capture, utilisation and sequestration, contributing to alleviating global warming. Previous studies have shown that the microporous structure of nanoparticles enhance the viscosity of a base fluid better than the counterpart of non-porous ones. A pinewood char with a specific surface area of 107 m 2 /g was selected to examine its viscosity enhancement in aqueous suspension and its EOR performance. Pinewood char nanofluids at a nanoparticle size of approximately 155 nm demonstrated a linear viscosity enhancement with charcoal concentration in the range suitable as flooding fluid. Sectional enhanced nanofluid flooding (0.2 pore volume of the core) into sand-packed cores demonstrated that a 0.125 wt% pinewood char nanofluid (viscosity 2.3 mPa∙s) achieved 51.4 % recovery of the residue oil in place. The nanofluids demonstrated excellent stability under ambient conditions. These findings highlight the feasibility of using charcoal-based nanofluids as a low-cost, renewable and carbon-negative EOR flooding fluids, offering a possible pathway towards more responsible hydrocarbon production that balances technical performance and environmental impact. • A charcoal from pinewood with the specific surface area of ~107 m 2 /g was selected for charcoal-based nanofluid preparation. • The aqueous nanofluids prepared with a particle size of ~155 nm showed strong viscosity enhancement, e.g., the nanofluid with 0.125 wt% of the char nanoparticles had the viscosity of 2.3 mPa•s at 20 °C. • The pinewood char nanofluids of 20 % of reservoir pore volume were applied in sectional flooding for enhanced oil recovery. • The 0.125 wt% pinewood char nanofluid recovered 51.4 % of remaining oil in place.