川东地区古生界主要泥页岩最高古温度特征

Maximum paleotemperature of main Paleozoic argillutite in the Eastern Sichuan Basin

泥页岩的热演化过程与其经历的古温度史相关,最高古温度决定它的最终热演化程度.本文利用古温标方法恢复了川东地区古生界主要泥页岩层系经历的最高古温度.研究结果表明,它们在距今80—90Ma时达到最高古温度,龙潭组顶面最高古温度150～220℃,龙潭组底面最高古温度160～230℃,龙马溪组顶面最高古温度160～250℃,五峰组底面最高古温度170～260℃,筇竹寺组顶面最高古温度210～320℃,筇竹寺组底面最高古温度210～320℃.各层最高古温度平面展布特征相似,最高温出现在涪陵—丰都一带,向南与向北温度均呈降低趋势,在达州—开江一带局部出现较高温.此外,结合川东地区古热流史分析认为,川东古生界泥页岩热演化过程具有阶段性,现今处于高-过成熟状态,达到最高古温度后生烃作用停止.川东地区经历较高的最高古温度随后快速抬升剥蚀有利于页岩气的成烃与成藏.

The thermal evolution process of argillutite is related to its paleotemperature history,and the final evolution degree is controlled by the maximum paleotemperature. We recovered the maximum paleotemperatures of main Paleozoic argillutite in the Eastern Sichuan Basin based on paleothermal indicators.These formations reached maximum paleotemperatures 80—90million years before present.The maximum paleotemperature of the top surface of the upper Permian Longtan Formation is150～220℃and bottom surface is 160～230℃.The maximum paleotemperature of the top surface of the lower Silurian Longmaxi Formation is 160～250 ℃ and the bottom surface of the upper Ordovician Wufeng Formation is 170～260 ℃.The maximum paleotemperature of the top surface of the lower Cambrian Qiongzhusi Formation is 210～320 ℃ and bottom surface is 210～320 ℃.The maximum paleotemperatures of these formations have similar distribution characteristics,exhibiting a high to low trend both to south and to north and the highest temperature appearing around Fuling-Fengdu with some high temperature areas near Dazhou-Kaijiang.The evolution processes of main Paleozoicargillutite in the Eastern Sichuan can be divided into different phases,and now is in the high to over mature stage.The Eastern Sichuan Basin experienced a high maximum paleotemperature,followed by rapid rise which is favorable for shale gas generation and accumulation.