Oil examination of two wells of the Upper-Salat deposit in Tomsk region has been carried out. The oils are sufficiently different in their composition. This fact determines the peculiarities of sludge formation in them. Oil paraffin hydrocarbons are presented by homologous series of normal alkanes with the number of carbon atoms С9-С30. For the oil of 122 well with high content of solid paraffins, bur distinguished by high concentration of resinous components, the process of sludge formation begins at T=+50 °С. In the oil of 188 well the sludge formation occurs at T=+70 °С