The Geochemical Character And Potential Of Hydrocarbon-producing Of Likely Source Rocks In The North Of North China

There are about 3,000,000km2 carbonate rocks covered in China, especially in North China, marine carbonate rocks of middle-upper Proterozoic group are widespread and its deposit layers are greatly thick. At the same time, Many outcrops of the asphalt and oil seepage indicate that appraisement of their hydrocarbon-bearing potential is an important subject to further study in middle-upper Proterzoic erathem strata. In this article, the author synthetically studies the characteristic of element compositions and organic carbon isotope compositions, organic matter abundance and hydrocarbon-bearing potential of the likely source rocks in middle-upper Proterzoic erathem strata, and further discusses their relationships.Through the research on the characters of element compositions of the likely source rocks, it can be inferred: (1) In the mass, most high-Ca carbonate rocks have low abundance of organic matter, while low-Ca argillaceous rocks is low abundance of the organic matter. But in some samples of Tieling and Xiamaling group, high-Ca rocks also have comparatively high organic matter abundance. (2) P, Cu, Zn, Ba, Ni element contents are better positive correlation with organic matter abundance, while Sr and Al2O3 being negative correlation, Fe-oxides are no correlation with the abundance of organic matter. The abundance of V is also good correlation with the organic matter abundance. Generally speaking, the enrichment of Cu, Zn, Ni, P, Ba are related to the inner matter of the earth, so the fluids of interior earth has some effect on the enrichment and preservation of the organic matter. (3) Organic carbon contents show good positive correlation withCu+Co+Ni, Al/(Al+Mn+Fe) and Ti/Fe. Because these elements content and their ratios in hydrothermal fluids of seabed shows greater than that in normal seawater, the hydrothermal fluids have some contribution to the enrichment of the organic matter.Studies on the character of organic carbon isotope compositions of the middle-upper Proterozoic likely source rocks show that: (1) Organic matter relatively enrich light carbon isotope, their 6 13C values varies from -26.8% to 34.4% and the compositions of carbon isotope of about eighty-five percent of samples range from -29% to-33.5%. Different lithologies have different organic carbon isotope compositions and the carbon isotope compositions of the muddy rocks are lighter than that of carbonate rocks. (2) The carbon isotope compositions of the kerogens are almost not affected by the thermal mature degree, while they are relatively good negative correlation with the total organic carbon. (3) We can infer that the organic matter may be derived from the biological assemblages, which are main marine algae; their kerogens combine sapropelic and humic-sapropelic. (4) The clear negative correlations between hydrogen index and the organic carbon isotope compositions indicate that hydrogen index is larger; the reduction of sedimentary environment of the source rocks is stronger. But the positive correlations between oxygen index and the organic carbon isotope compositions show that oxygen index is larger, the oxidation environment is stronger. (5) With the advancement of geological age, the organic carbon isotope compositions gradually become heavy from Chuanlinggou, Tuanshanzi group to Dahongyu group, while the organic carbon isotope compositions of Jixian and its above beds gradually become light. Xiamaling, Tieling and Hongshuizhuang group are more enriched light carbon isotope than that of the other group.It can be inferred from the analyses of the organic matter abundance and hydrocarbon-forming potential that: (1) the organic carbon contents in likely source rocks differ from 0.03% to 16.47%, and the organic carbon contents of some forty-one percent samples are larger than 0.5%, their deposit layers contain Xiamaling, Tieling, Hongshuizhuang group, while the organic carbon contents of Gaoyuzhuang and Wumishan groups are lower than 0.5%. (2) The oil-bearing potential of likely source rocks range from 0.2mg/g to 84.83mg/g...