Single-step silica nanofluid for improved carbon dioxide flow and reduced formation damage in porous media for carbon utilization

Water-alternating gas (WAG) is affected by viscous fingering (with too much gas) and trapping of reservoir oil (with too much water) that can be addressed by advanced methods such as nanofluids, those not only increase CO2 capturing but also provide significant control on fingering. Therefore, this study reports the use of single-step silica nanofluids, of controllable nanoparticle (NP) size (below 100 nm), for improved CO2 flow and reduced formation damage in porous and permeable media. Polyacrylamide (PAM, 1000 ppm) was used as viscosifler and found favorable for enhanced dispersion stability (more than 2 months) in nanofluids. The parameters, such as amount of precursor (Tetraethylorthosilicate-TEOS) and catalyst (ammonium hydroxide-NH4OH), and amount of PAM were varied. Silica NPs were highly stable against agglomeration as reported by DLS, FTIR, TEM, SEM, and UV methods. Silica Nanofluids delayed CO2 breakthrough by retaining CO2 in sand-pack for longer duration than water/PAM. CO2 in presence of NPs made stable foam that was viscous and least mobile (than CO2) as confirmed by progressive increase in pressure while CO2 flow with water/PAM was unstable as pressure varied nonuniformly. This is of key importance for CO2 sequestration studies in porous reservoirs. Since NPs are solid substances, they can retain in sand-pack during nanofluid use for CO2 utilization strategies. NP retention was determined experimentally for different (1) sand-pack length, (2) flow rate, (3) NP concertation, and (4) test temperature. NP retention of only 8-12% of total injected amount was reported with Sand-pack length as the most influential variable. (C) 2020 Elsevier Ltd. All rights reserved.