中国原油的地球化学特征——兼论中国原油的有机与无机来源

中国大庆、辽河、大港、新疆等油区原油的地球化学组成显示以下特征 :含有地壳稀少而地球深部丰富的元素 ,如Re、In、Cd、Ag、Au等 ;含有生物质平均成分不见的元素 ,如Be、Ga、Zr、Nb、Sb、Te、Hf、Ta、W、Tl、Bi、Th等 ;含有较多的亲石元素 ,如Ca、Mg、K、Na、V、Li、Be、B、Ti、Cr、Mn、Rb、Sr、Y、Zr、Nb、Cs、Ba、Hf、Ta、W、Th、U等 ;原油的正烷烃结构具有奇偶优势与不显奇偶优势的特征 ,不显奇偶优势的原油沿基底断裂分布。地球化学特征是矿产资源形成途径的示踪标志。中国原油中含有生物质中不见的元素 ,说明原油可能有来自非生物成因的油源 ;含有地壳稀少而地球深部丰富的元素 ,说明原油可能有来自地球深部成因的油源 ;含有较多的亲石元素 ,说明原油可能不是从生油岩中排出的 ,而是从非岩石结构的地球深部流体中分异后聚集在岩石结构的孔隙中而形成油层的。原油的正烷烃结构显示的奇偶优势被认为系生物成因的油源 ,而不显奇偶优势被认为是甲烷石油 (即来自地球深部的无机成因油源 ) ,不显奇偶优势的油样均沿基底断裂分布 ,正旁证了地球深部来源的可能性。

GEOCHEMICAL CHARACTERISTICS OF OILS IN CHINA--A PROBE INTO THEIR ORGANIC AND INORGANIC SOURCES

The geochemical compositions of crude oils from the Daqing, Liaohe, Dagang and Xinjiang oilfields of China show the following characteristics: they contain the elements which are rare in the crust but abundant in the mantle, for instance Re, In, Cd, Ag, and Au; they contain the elements such as Be, Ga, Zr, Nb, Sb, Te, Hf, Ta, W, Tl, Bi and Th, which are invisible in biogenic materials; they contain more lithophile elements such as Ca, Mg, K, Na, V, Li, Be, B, Ti, Cr, Mn, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, W, Th, U, etc.; the normal alkane structure of crude oils possesses odd-even predominance but displays no odd-even predominance, and crude oils with no odd-even predominance are distributed along the basement fault. Geochemical characteristics are the important indicators of forming path of mineral resources. The existence of the elements which are invisible in biogenic materials indicates the crude oils may be derived from non-biogenic crude oils. In addition, the fact that the crude oils contain the elements which are rare in the crust but abundant in the mantle demonstrates that they may have come from crude oils originated in the deep interior of the earth. The presence of more abundant lithophile elements indicates that the crude oils may have not expelled from source rocks, instead, they may have derived from non-rock textural fluids in the deep interior of the earth and then accumulated in the pores of rocks following differentiation, forming oil reservoirs. The odd-even predominance indicates that the crude oils are of biogenic origin, and no display of odd-even predominance indicates the crude oils are methane-derived oils (from crude oils of inorganic origin in the deep interior of the earth). The oil samples that do not display odd-even predominance are all distributed along the basement fault, providing indirect evidence for their inorganic origin in the deep interior of the earth.