Asphaltene instability during CO2 injection and pressure depletion leads to interfacial restructuring and pore-scale blockage in carbonate reservoirs. Here, a new green KCl/SiO2/Xanthan/Pistacia atlantica nanocomposite (NCs) is evaluated for its ability to inhibit asphaltene precipitation through coupled interfacial tension (IFT), surface, and flow interactions. High-pressure microscopy directly visualizes that at the IFT transition pressure (2300 psi), the base oil forms 2–5 μm asphaltene aggregates, whereas the nanocomposite-treated oil contains only sparse <2 μm particles. This visual evidence supports the observed change in CO2-oil IFT: the post-transition IFT slope ratio increases from 26.5% (base) to 37.1% with 30 ppm NCs, indicating delayed interfacial accumulation. Adsorption isotherms give a Langmuir capacity of 222.2 mg/g. Control experiments (SiO2 alone, xanthan alone, binary SiO2+xanthan) show that the full nanocomposite reduces asphaltene precipitation by 2.42 wt.% (absolute), confirming true synergy. AFM analysis reveals a decrease in root-mean-square roughness (Rq) from 77.5 nm (base) to 35.1 nm (NCs) (p < 0.01), indicating constrained asphaltene cluster growth. Under pressure depletion, the nanocomposite reduces asphaltene precipitation by 31.6% at 3800 psi (from 7.67 to 5.25 wt.%). Core flooding (duplicate runs) shows that the NCs-treated core preserves a normalized permeability of k/k0 = 0.55 after 10 PV, while the base core drops to 0.30. Pressure build-up is slower (∼65 psi vs. ∼110 psi) and porosity retention is higher (88% vs. 84%). Post-flood brine injection recovers 92% of initial permeability, indicating no permanent plugging by NC particles. Overall, the direct visual, adsorption, surface, and core-flow evidence demonstrates that the NCs reduces asphaltene precipitation, delays interfacial aggregation, lowers surface roughness, and preserves permeability in carbonate cores under the tested conditions. The multi-component structure provides a synergistic effect not achieved by any single component alone.
