松辽盆地上古生界烃源岩特征及有效性分析

Characteristics and Validity Analysis of Hydrocarbon Source Rocks of Upper Paleozoic in Songliao Basin

松辽盆地石炭系—二叠系烃源岩经历了较为复杂的构造演化,不同地区烃源岩的埋藏史、热演化史及生烃史不相同。通过对收集的资料和采集的上古生界烃源岩样品进行地球化学分析,探讨了松辽盆地不同地区石炭系—二叠系烃源岩演化特征及其有效性。结果表明:松辽盆地上古生界烃源岩有机质丰度低,有机质类型较差(主要为Ⅲ型和Ⅱ2型),现今热演化程度高(已达到成熟和过成熟阶段),后期生烃潜力有限,但不代表地质历史时期生烃贡献小;肇源、长岭地区上古生界烃源岩为后期深埋藏型,存在二次生烃,为上古生界有效烃源岩主要分布区,对天然气资源有贡献;杜尔伯特地区由于受周边侵入岩烘烤、后期浅埋深等因素的影响,古地温远高于现今地温,不能发生二次生烃,烃源岩基本无效。因此,松辽盆地肇源、长岭地区为上古生界烃源岩有利生气区。

The tectonic evolution of Carboniferous-Permian source rock in Songliao Basin is relatively complex, so that the burial history, thermal evolution history and hydrocarbon generation history of source rock are not same in different regions. According to the collected data and the geochemical analysis for the samples of Upper Paleozoic source rock, evolution characteristics and validity of Carboniferous-Permian source rock in different regions of Songliao Basin were discussed. The results show that the Upper Paleozoic source rocks, which have already reached mature and over-mature stages and thus lead to limited hydrocarbon generation potential in later period, are of low abundance of organic matter with poor types III and II1 in Songliao Basin, but the contribution to hydrocarbon generation during the geological history is not always little; Upper Paleozoic source rocks in Zhaoyuan and Changling areas, which are the main distribution areas of Upper Paleozoic effective source rocks, are deeply buried in the later period with the secondary hydrocarbon generation and contribute to the natural gas resources; the source rocks in Dorbod area are affected by the warm-effect from surrounding intrusive rocks and shallow burial in later period, so that the paleotemperature is far higher than the present temperature, and the source rocks are invalid without secondary hydrocarbon generation. Therefore, Zhaoyuan and Changling areas are favorable for gas production of Upper Paleozoic source rocks in Songliao Basin.