Key words: the drilling fluid, the secondary crystallization, beds of precipitation, salt core, the modifier.
The paper examines the factors that determine the nature of the decline in boreholes at the opening of halogen salts of great thickness. Raises issues related to the valuation of drilling mud during drilling in the beds of precipitation. The article contains the thermodynamic expression of the secondary crystallization process; salt in the borehole wall affects the choice problem requirements modifier medium mud to prevent secondary crystallization. The results can be used to solve the problem of preventing the narrowing of the wellbore due to secondary crystallization of salt on the walls.