The type of source organic matter of West Siberian oils localized at depths of 1425 to 3950 m in Cretaceous, Jurassic, and Paleozoic deposits is determined based on the composition of bio- and geomarkers. The individual and group compositions of alkylnaphthalenes of these oils are studied. The geochemical parameters of oil transformation are calculated from the composition of methyl-, dimethyl-, and trimethylnaphthalenes. Data on the individual composition of alkylnaphthalenes are processed by the method of principal components of factor analysis. The matrix is compiled of 44 oils and 22 characteristics (contents of individual alkylnaphthalenes). The molecular-mass distributions of alkylnaphthalenes in oils of different genesis served as a basis for the separation of the latter into families according to the compositional similarity of biarenes and the degree of oil transformation.