Intelligent control of emulsion stability and evaluation of selective water shutoff performance

Using hydrophobic nano-SiO2 and a tiny amount of non-ionic and anionic surfactants as stabilizers, a Pickering emulsion system for oil -in -water in high -temperature and high -mineralization reservoirs was developed. At high temperatures (120 degrees C) and high mineralization (37000 mg/L), the emulsion system shows outstanding stability. The addition of the auxiliary agent can effectively control the time of emulsion breaking and nanoparticle release. The auxiliary agent will "compete" with the surfactant for adsorption on nanoparticles at the oil/water interface, weakening the surfactant's anchoring effect and causing a decrease in the surface roughness of the nanoparticles, resulting in a decrease in the mechanical strength of the interfacial film. Furthermore, the presence of H+ in the solution neutralizes part of the negative charges on the surface of emulsion droplets, which is detrimental to emulsion stability because electrostatic repulsion between droplets is diminished. The released SiO2 particles agglomerate in the pore throat to form a hydrophobic filter cake, which can be used to achieve intelligent water control in high -temperature and high -mineralization reservoirs (1000 mD), with an aqueous phase plugging rate of 95.83% and an oil phase plugging rate of 25.32%.