Distribution of trace elements in crude oils from southern Germany

Abstract

The concentrations of the elements S, V, Cr, Fe, Co, Ni, Zn, Se, Br, I, Ag and Hg were determined in 45 crude oil samples of 17 oilfields originating from nine different Mesozoic or Tertiary reservoir rock formations in the southern German Alpine Foreland. Furthermore, the elements Na, Mg, S, Cl, Ca, Fe, Co, Cu, Zn, Br, Sr and I were determined in 15 oilfield water samples. The analytical technique was mainly instrumental neutron-activation analysis; to a minor degree X-ray fluorescence spectrometry, atomic absorption and emission spectrometry as well as titrimetric methods were applied.The amounts of S, V, Ni and Se are relatively constant in the different oilfields; therefore they are suitable for distinguishing between different classes of oil. The crudes can be divided into the following three significant groups by their concentrations of S, V and Ni: 1.(A) Triassic and Lower Jurassic crudes of the Western Molasse Basin.2.>(B) Crudes from the Bausteinschichten (Lower Chattian) in the Western Molasse (except the one from Aitingen). In the Eastern Molasse crudes from Priabonian sands, Malm and Lower Cretaceous.3.(C) Secondary altered crudes of the “Ampfinger Schichten” in the Eastern Molasse Basin.The crudes of Aitingen are exceptional with their high content of S and V, being enhanced three and twenty times, respectively.Relations between trace-element distributions in crudes and in accompanying oilfield waters could not be found. Only the amounts of I in crudes are significantly correlated with those from the corresponding oil field waters.