Generative Potential of Carboniferous-Permian Coal-Bearing Source Rocks in Ordos Basin

摘要

The organic matter abundance, type and maturity have been studied along with their generative potential in coals, carbonaceous mudstones and mudstones from Carboniferous-Permian in Ordos Basin, revealing that the coal-bearing source rocks in the study area have the stronger generative potential. The source rocks are typically humic gas source rocks with the main source rock dominated by the coals. There are significant diversities in the generative potential in different lithological source rocks. The generative potential decreases in the following order: coals, carbonaceous mudstones, mudstones. The desmocollinite in vitrinite group shows a positive correlation with hydrogen index (I_H) or S₁ + S₂ values, indicating the desmocollinite in coal may be the major contributor to hydrocarbon generation. On the whole, the hydrogen index and S₁ + S₂ values both exhibit a good relationship with the desmocollinite in carbonaceous mudstones or mudstones, whereas they have a >poor correlation with the pristane/phytane ratios. The hydrogen index and S₁ + S₂ values in coal with the increased pristane/phytane ratios in coal both increase at first and then decrease, whereas they both have a poor correlation with the desmocollinite. These results show that the generative potential in coal is mainly related with the sedimentary environment, while the hydrocarbon generation matter is the main factor influencing the generative potential in carbonaceous mudstones or mudstones.