A novel polymer encapsulated silica nanoparticles for water control in development of fossil hydrogen energy—tight carbonate oil reservoir by acid fracturing

This paper introduces and evaluates performance of a novel polymer encapsulated silica nanoparticles (CM-NPs) as RPM on reducing water-cut in tight carbonate oil formations with multistage hydraulic fractures. CM-NPs as RPM were prepared by graft-polymerization and quaternization and then identified by FT-IR method. Changes in the core surface properties and oil/water relative permeability were identified by SEM, XPS, wettability measurements and core flooding experiments. Certain changes occur, as confirmed by SEM and XPS, in the element compositions and microstructure of the core surface after introducing CM-NPs on the reservoir rock surface. Such changes irreversibly alter its wettability from the hydrophobicity to hydrophilicity. During the displacement experiments, there exists a disproportionate permeability reduction on relative permeability of the oil-water systems. Because of microstructure change of core surface, water relative permeability is reduced up to 60% and water flow restricted by hydrophilic polymer chains on the surface of CM-NPs while oil relative permeability decreases by less than 15% at different stages of water saturation. In addition, the rheological measurements and water drive tests shows the CM-NP solution has good acid resistance and strong adsorption on the core surface, keeping a long-term period of water control after acid fracturing in tight carbonate oil reservoir.