The present invention relates to methods of generating gas in and foaming well treating fluids during pumping of the treating fluids or after the treating fluids are placed in a subterranean zone, or both. A method of the present invention provides a method of making a foamed well fluid that comprises a gas comprising the steps of combining an aqueous fluid, a surfactant, an encapsulated activator, and a gas generating chemical, the gas generating chemical being present in an amount in the range of from about 0.1% to 100% of a water component in the aqueous well fluid; and allowing the gas generating chemical and the encapsulated activator to react so that gas is generated in the aqueous fluid to form a foamed well fluid. Methods of cementing, fracturing, cementing compositions, fracturing fluid compositions, and foamed well fluid compositions also are provided.