THE GEOCHEMISTRY CHARACTERISTICS OF METALLO-PORPHYRINS IN TERRESTRIAL CRUDE OIL

The terrestrial crude oil of China contains nickel porphyrin but none vanadyl porphyrin, detected by UVS ESR and elements analysis. In 11 basins, such as Junggar., Qaidam, Jianghan, Songliao etc., the Ni-porphyrin content in Cainozoic crude oil is higher than that in Mesozoic. Ni-porphyrin content has not obvious relation to the increase and decrease of resines, asphaltenes and sulfurs. But if the crude oil was occured from saline lake-basin the content of Ni-porphyrin would be higher. The vanadyl-porphyrin is mostly distributed in the factions of non-hydrocarbons and asphaltenes of the crude oil. The Ni-porphyrin is mainly distributed in alomatic fraction, but less in the fraction, of non-hydrocarbons. In the crude oil of hypergene-oxidized zone, the vanadyl porphyrin trends to increase, but Ni-porphyrin does not. In catagenesis stage of the crude oil, the thermal stability of Ni-porphyrin is lower than that of vanadyl porphyrin(the velocity of thermal degradation of Ni-porphyrin is faster than that of vanadyl porphyrin). The Ni-porphyrin is higher in low-maturity crude oil and lower in mid-maturity crude oil, but none in high-maturity crude oil and condensate. During the conversion of organic materials into oil-gas the time of Ni-porphyrin formed is earlier than a large quantity of hydrocarbons formed. With the increase of depth, the kerogen can convert into hydrocarbons by the thermal degradation, but it can't generate Ni-porphyrin, contrariwise, with the increase of temperature its content gradually disapears from decrease because of the characters of its thermal stability. Without doubt, the texture of Ni-porphyrin also occurs some changes correspondly. Therefore, Ni-porphyrins of crude oil were derived from the pigments of original organic materials during the stage of diagenesis.