Pore-scale insights into the effect of surface-modified nanosilica on invert-emulsion drilling-fluid and formation damage.

This article investigates formation damage mechanisms caused by the invasion of invert-emulsion oil-based drilling fluids (OBMs) at the pore scale and evaluates damage remediation using silica nanoparticles with varied surface chemistries. Using microfluidic glass micromodels, the study identifies two damage types: primary damage from emulsion breakage, water blockage, and particulate deposition immediately after drilling fluid invasion, and secondary damage during acid treatment and oil flowback, including acid trapping, sludge, and acid-in-oil emulsions. The research demonstrates that nanoparticle additives, particularly hydrophobic silica nanoparticles such as PGPTS (propyl silane combined with 3-glycidoxypropyl-triethoxy silane), improve drilling fluid stability, reduce formation damage, and optimize rheological properties, with optimal nanoparticle concentrations decreasing as hydrophobicity increases. The 0.5 wt. % PGPTS nanofluid showed the least formation damage, indicating that surface chemistry modification has a greater impact on fluid stability and damage mitigation than nanoparticle concentration alone. These findings provide pore-scale insights into OBM-induced formation damage and suggest that nanoparticle-enhanced drilling fluids can effectively reduce damage during the well life cycle.