FEATURES OF THE COMPOSITION OF CRUDE OILS FROM FIELDS OF THE ULYANOVSK AREA AND THE DISTRIBUTION IN THEM OF VANADIUM-CONTAINING AND OTHER HETEROELEMENTAL COMPOUNDS

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 a nd its southern part with respect to the content of asphaltene-resinou s substances, sulphur and, in particular, vanadium and nickel, the con centrations of which for the northern fields are abnormally high (simi lar to 1000 g/t). This is due to the special conditions under which th e formations were created, promoting processes of metal accumulation b y 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 w ith components of asphaltene-resinous substances, whereas most organos ulphur 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, requ iring considerable energy consumption for their extraction.