A fracturing system for a well, in which a stream of LPG, a mixture of propane and butane, is injected into the well at frac pressure. Proppant is supplied into the LPG stream, and carried by the LPG mix into the formation. Inert gas such as nitrogen is used for purging system components of LPG, and to help protect against risk of explosion. Nitrogen may also be added to the LPG mix during a frac of shale gas or coal gas formations.