Interfacially regulated bio-based reactive Pickering emulsions for pore-scale curing control and low-damage consolidation of unconsolidated sandstone

Improving the consolidation strength of unconsolidated sandstone while reducing permeability impairment during sand consolidation is important for the long-term stable development of sand-producing reservoirs. To mitigate the conflict between strength enhancement and pore-throat damage in conventional resin-based sand consolidation, a bio-based reactive Pickering emulsion sand-consolidation system based on oil–water interfacial regulation was developed in this work. N-(n-butyl)-3-aminopropyltrimethoxysilane (EB-1189)-modified nano-SiO 2 (EBS) was used as the particulate stabilizer at the oil–water interface. First, EBS particles with different degrees of surface modification were prepared. Their surface structure, thermal behavior, wettability, and emulsion-stabilizing ability were evaluated by FT-IR, TGA, XPS, contact-angle measurements, and droplet-size analysis. The results showed that EBS-6 had a water contact angle of 70.7 ± 0.8°. It provided a good balance between aqueous dispersibility and oil-water interfacial adsorption. The emulsion stabilized by EBS-6 showed smaller droplets and a narrower droplet-size distribution. Then, Pickering emulsions with different particle loadings, denoted as EBSR, were prepared using epoxidized linseed oil (ELO) and 1,3-bis(aminomethyl)cyclohexane-methyl isobutyl ketone ketimine (1,3-BAC-MIBK) as the core reactive components. The chemical structure and high-temperature stability of EBSR were confirmed by FT-IR, TGA, and XPS. Emulsion stability and rheological tests showed that EBSR-3 had better injectivity and stability at 80 ℃. Its gel time and initial curing time were about 11.8 h and 15.2 h, respectively. Core flooding tests using field unconsolidated sandstone cores showed that EBSR-3 achieved permeability retention values of 89.86% after curing and 90.28% after long-term water flooding. Its compressive strength reached 6.83 MPa after curing and remained at 5.98 MPa after long-term water flooding, with a strength retention ratio of 87.55%. Micro-CT results showed that EBSR-3 better preserved pore-throat connectivity and main flow channels. SEM observations further showed coating-like cured products on sand-grain surfaces and intergranular cementation bridges at grain-contact regions. These results suggest that EBS-mediated oil–water interfacial stabilization and the resulting regulation of curing behavior may help reduce extensive accumulation of cured products within the main pore-throat space while promoting effective intergranular cementation, thereby contributing to the balance between consolidation strength and permeability retention. This system provides a new bio-based Pickering-emulsion strategy based on oil–water interfacial regulation for low-damage sand consolidation in unconsolidated sandstone reservoirs. Download: Download high-res image (251KB) Download: Download full-size image