Inorganic Geochemistry of Oil: First Results of the Study Using the ICP-MS Method of the East-European and West-Siberian Oil Deposits

Kirill S. Ivanov¹, Yuriy N. Fyodorov², Yuriy L. Ronkin³, Yuriy V. Yerokhin³, Ogla E. Pogromskaya³, and Irina N. Plotnikova⁴

¹Institute of Geology and Geochemistry of Russian Academy of Sciences, Ekaterinburg, Russia ²Tumen Department of KogalimNIPIneft, Russia

³Russian Academy of Sciences

⁴Department of Geology of Tatarstan, Russia

New data have been obtained from 59 rare, rare-earth and other elements in crude oil deposits in West Siberia and the giant Romashkino field of the Tatarstan Republic. ICP-MS analyses have been made with a high resolution mass-spectrometer ELEMENT 2. The principle geochemical anomalies in these samples include limitedly low contents of most elements, except for the elements V, Ni, Cr, Ca, Sr, Na, Rb, Cs. The West-Siberian oils manifested a PGE (platinoid) presence in substantial quantities, especially of Pd. When normalized on the contents of a primitive mantle [Taylor, McLennan, 1985] positive anomalies of U, Sr, Ti, Y, Zr, have been observed in these oils and negative anomalies on Sm, Hf, Th, Nb, Nd. The rare-earth elements in the West Siberian oils demonstrate a particular type of trend characterized by enrichment of the light lanthanides (La/Yb=16-19) and a sharply positive Eu anomaly. The crude oil samples of the Romashkino deposit, when similarly normalized against the primitive mantle distribution in oil of rare earth and minority elements, manifest positive anomalies of Sr, Rb, Cs, Hf, Zr, Eu, U and negative anomalies of Ti and Th. The contents of PGE are about one order lower in the Romashkino crude oil than in the West-Siberian. Rare-earth elements in the Tatarian oil show approximately a trend with gradual enrichment of light lanthanoids with high La/Yb ratio up to 20 units and the presence of a sharply positive Eu anomaly. Oils from West Siberia and Tatarstan are of different geochemical types. The elemental distributions in the crude oil from all deposits studied do not match such of any known crustal rock. The experimental data presented should be taken into consideration when considering the origin of oils.