The general formulation of a two-phase multicomponent filtration model which describes all stages of indicator studies of multi-stage fracturing on horizontal wells is given. The equations of the model are presented in a dimensionless form with normalization to the characteristic scales. The statements of the direct problem and the inverse problem of interpreting the results of tracer studies are presented. Simplification of model based on the analysis of the characteristic scales and sizes of the similarity criteria that determine the solution of the problem is shown. Simplification includes transition to quasistationary equations for the average values of saturation and concentration of tracers in fractures and in the wellbore and decomposition of three-dimensional problems for pressure, saturation and tracer concentrations in the reservoir into a set of one-dimensional problems near fracture faces. The presented simplification of the model is intended for a reduction of numerical simulation computational costs, which makes it possible to construct a solution of the inverse problem for interpreting tracer studies based on a multivariate solution of direct problems.