The problem of preventing cave-in of the walls of boreholes can be effectively and economically solved only with a broad assortment of flushing fluids (FF) of the corresponding quality. In order to search for inexpensive and simple methods of preparing and formulas of FF which have good stabilizing properties, the authors conducted laboratory studies. It is indicated that this goal can be reached by three methods: 1) improvement in the properties by traditional (based on gypsum and lime) FF by additives (for example, chloride, acetate and potassium dihydrophosphate); 2) production of FF of the limestone type based on new theoretical concepts regarding the mechanism of their effect, and 3) by using as the FF ammonium-containing chemical compounds (for example, diammonium hydrophosphate). The studied FF were tested under field conditions and yielded positive results. It was established that different specific conditions of the wells make it necessary to systematically study clays and marls in the drilling zone in order to select the most effective and economical for the given conditions of FF. This will permit the maximum use of local raw material and selection of the simplest method of preparing FF.