An investigation has been made of the crude oils of a number of fields of the Ul＇yanovsk area. Considerable differences were established in the composition of crude oils from fields of the north of the region and its southern part with respect to the content of asphaltene-resinous substances, sulphur and, in particular, vanadium and nickel, the concentrations of which for the northern fields are abnormally high (similar to 1000 g/t). This is due to the special conditions under which the formations were created, promoting processes of metal accumulation by migration mechanisms. The main forms in which vanadium is found are vanadyl complexes (VC), a considerable proportion of which are in the form of vanadyl porphyrins. Vanadyl complexes are chiefly associated with components of asphaltene-resinous substances, whereas most organosulphur compounds in crude oils are concentrated in their oil fractions. With the polyaromatic structures of fragments of asphaltene-resinous substances, vanadyl complexes form associates with strong bonds, requiring considerable energy consumption for their extraction.