Nano-foam oil washing agent for CO2 flooding of low-permeability reservoir as well as preparation method and application of nano-foam oil washing agent

The invention provides a nano-foam oil washing agent for CO2 flooding of a low-permeability reservoir as well as a preparation method and application of the nano-foam oil washing agent, and belongs to the field of oilfield chemistry. The nano-foam oil washing agent for synergistic CO2 flooding of the low-permeability reservoir, provided by the invention, comprises the following components in percentage by mass: 20-25% of a nano-surfactant, 12-22% of an anionic surfactant, 15-20% of a nonionic surfactant, 5% of low-carbon alcohol and the balance of water. The foam oil washing agent provided by the invention can be effectively applied to a low-permeability oil reservoir with the formation water mineralization degree of less than or equal to 100000mg/L, the calcium and magnesium ion concentration of less than or equal to 2000mg/L and the permeability of (0.1-50) * 10 mu m < 2 >, the CO2 flooding effect is enhanced, the problems of CO2 flooding gas channeling and relatively poor oil washing rate on heavy co