High-temperature-resistant and high-salt-resistant dual-crosslinking foaming agent suitable for geothermal stratum as well as preparation method and application of foaming agent

The invention provides a high-temperature-resistant and high-salt-resistant dual-crosslinking foaming agent suitable for geothermal stratums as well as a preparation method and application of the foaming agent. The preparation method comprises the following steps: mixing an anhydride monomer and an arylphenol polyoxyethylene ether compound, stirring until the anhydride monomer and the arylphenol polyoxyethylene ether compound are dissolved, heating to a reaction temperature, adding a catalyst A under the protection of nitrogen, and reacting to obtain a monoester polymer; mixing the monoester polymer, a hydroxyl-containing monomer and a benzene ring-containing vinyl monomer, stirring until the mixture is dissolved, heating to a reaction temperature, and adding a catalyst B and an initiator under the protection of nitrogen to react to obtain a diester polymer; and adding the diester polymer into water, adding a sulfonated compound, heating to a reaction temperature, adding a catalyst C under the protection of n