柴北缘下奥陶统烃源岩有机地球化学特征

ORGANIC GEOCHEMICAL CHARACTERISTICS OF LOWER ORDOVICION HYDROCARBON SOURCE ROCKS IN THE NORTHERN FRINGE OF CHAIDAMU BASIN

柴北缘下奥陶统多泉山组发育暗色碳酸盐岩 ,石灰沟组发育暗色泥岩 ;从实测的残余有机碳、生烃潜量与理论上恢复后的原始有机碳、生烃潜量来看 ,研究区暗色碳酸盐岩为非烃源岩 ,而暗色泥岩则为较好—好的烃源岩。沥青反射率及储层的包裹体均一化温度显示 :下奥陶统烃源岩有机质演化处于高成熟阶段。生烃史分析表明 ,烃源岩中有机质在奥陶纪末期—志留纪早期曾有一次短暂的成烃期 ,在二叠纪末—三叠纪进入生油主期 ,到白垩纪进入高成熟阶段 ;包裹体均一化温度反映油气成藏期位于中生代晚期—新生代。

The dark carbonate rocks in Duoquanshan Formation and dark mudstones in Shihuigou Formation of Lower Ordovician are the potential hydrocarbon source beds in the northern fringe of Chaidamu Basin. Through comparing the measured residual organic carbon and potential hydrocarbon generation amount with the theoretically restored organic carbon and potential hydrocarbon generation amount, it was considered that in this region the dark carbonate rocks are not hydrocarbon source rocks but the dark mudstones are the fairly good or good hydrocarbon source rocks. According to the data on the bitumen reflectance and inclusion homogenization temperature, it is shown that the organic matters in Lower Ordovician source rocks are in the high maturity stage. The analysis of hydrocarbon generation history indicates that the organic matters in hydrocarbon source rocks had had a short hydrocarbon generation time in Late Ordovician-Early Silurian, entered into the main oil-generation in Late Permain-Triassic and reached to the high maturity stage in Cretaceous. The data on the inclusion homogenization temperature show that the oil and gas reservoirs were formed in Late Mesozoic-Cenozoic.