Organic–Inorganic nanocomposite microspheres with enhanced mechanical stability for deep reservoir profile control

Polymer gel microspheres are promising agents for in-depth profile control in heterogeneous reservoirs, but conventional polymer microspheres (CPMs) are susceptible to mechanical damage during injection and repeated extrusion through pore throats, resulting in poor long-term plugging stability. Herein, we report shear-resistant organic–inorganic nanocomposite microspheres (NCMSs) prepared by inverse emulsion polymerization using a long-chain hydrophobic associative monomer and cetyltrimethylammonium bromide-modified montmorillonite. Reversible hydrophobic associations and rigid CTAB-MMT nanosheets provide complementary mechanisms for stress dissipation and structural reinforcement, respectively, thereby improving microsphere stability while preserving pore-throat deformability. NCMSs-0.5 retained 97.30 % of their initial D50 after five consecutive passages through a 12 μm micropore plate and exhibited good particle-size stability under elevated-temperature, high-salinity, and repeated pore-throat deformation conditions. After 180 days of aging, their apparent pressure-bearing strength remained 11.31 MPa, approximately 4.3 times that of CPMs. NCMSs achieved plugging efficiencies of 92.59–94.31 % and increased the liquid-production fraction of the low-permeability core from 13.83 % to 47.14 %, with its final oil recovery reaching 23.61 % compared with 14.47 % for CPMs. Microfluidic visualization further revealed deformation-assisted pore-throat passage and bridging retention. This work provides an effective organic–inorganic network design for durable deep profile control and enhanced oil recovery in heterogeneous reservoirs.