The structural group composition of paraffin-naphthenic and aromatic hydroc
arbons isolated from the Ishimbaiskoe residual oil was studied by the mass
spectral technique. It was found that the Ishimbaiskoe residual oil contain
ed half as much again the amount of higher normal paraffins and monocyclic
naphthenes in the corresponding topped produced oil that the but had lower
amounts of isoparaffins and total tetra-, penta-, and hexanaphthenic hydroc
arbons. Of the aromatic hydrocarbons from the residual oil, those of a hybr
id structure prevail. The component type contents of residual and topped pr
oduced oils from the Ishimbaiskoe and Urshakskoe fields of Bashkortostan we
re compared.