Formation scale may be resulted in permeability decrease greatly, especially in low or ultra-low permeability reservoirs. A nanoemulsion with very small particle size, ultra-low interfacial tension and highly penetration possesses good properties in formation antiscaling. The antiscaling ingredient is slowly released from the nanoemulsion, which prolongs the effect time of antiscaling. The colloidal particles are able to quickly and effectively reach the target layer because their sizes are smaller than the rock pore throats. Nanoemulsions also dissolve or disperse big liquid droplets and organic impurities, which may regain rock permeability. In the work, with a green surfactant fatty acid methyl ester sulfonate (MES) and a biodiesel fuel, the optimal formation conditions of MES middle phase microemulsion were obtained by the orthogonal design experiments as follows: CMES = 10.0~12.0g/mL, Cn-butanol=12.0g/mL, CNaCl=6.0g/mL; The effects of concentrations of NaCl and n-butanol, and the type of alcohols on the microemulsion phase behavior, the optimal salinity (S*) and the length of salinity (ΔS) were investigated.
An antiscaling nanoemulsion was prepared by three kinds of antiscaling ingredients FG-1, FG-2 and FG-3 dissolved in water phase. The antiscaling rates of two nanoemulsions with antiscaling ingredients FG-1 and FG-2 are 90.1% and 89.6%, respectively. There are no flocculates contacting with the formation water. The nanoemulsion with FG-2 possesses good adsorption, slow desorption rate and good antiscaling performance under high salinity. Compared to the present scale inhibitors, the antiscaling rate of nanoemulsion has a peak value, which greatly increases the useful effect time of scale inhibitor, and improves the anti-scaling effect and repairs permeability of rock. There is a good prospect for controlling the formation damage in low or ultra-low permeability reservoirs and water-sensitive formation.