It is stated, that horizontal wells' drilling efficiency at the oil and gaz fields with seismic-tectionic activity greatly depends on correct determination of their structural location and selection of most stable design for production wells. Conclusion is made on expediency of clay mineral composition studies of production wells' sections with the purpose of quantative evaluation of their hydrophilic minerals content. it is noted, that such data is useful for solving problems, connected with elimination of drift sands negative influence on production casing stability.