合肥盆地烃源岩有机质热演化历史分析

Thermal Evolution History Analysis of Source Rocks of Hefei Basin

利用镜质体反射率资料及其定量恢复的合肥盆地的古地温结合伊利石结晶度测定系统研究了盆地石炭—二叠系以来的热演化史,在此基础上分析了石炭—二叠系、下侏罗系、中上侏罗系、白垩系、古近系的烃源岩有机质的热演化程度及热演化史,结果表明合肥盆地C—P系呈现为高成熟阶段,并在下侏罗统沉积之后开始进入生油门限,在上侏罗统沉积后地温曾达245℃,而在白垩纪中期(朱巷组沉积后)最大古地温度达到过305℃指示进入了过成熟阶段。下侏罗统防虎山组Ro值和伊利石结晶度也显示了较高的热演化程度,在中侏罗统沉积后开始进入生油门限,在早白垩世朱巷组沉积后达到了最高的热演化程度,最大古地温达260℃。中—上侏罗统随着下白垩统朱巷组的沉积而进入生油门限,在下白垩统沉积之后达到了最大的古地温度,分别为225℃、230℃,指示开始进入过成熟阶段,朱巷组最大埋藏温度出现在早白垩世末,达到了110～120℃,指示进入了成熟期。在上覆古近系沉积后曾达到最大古地温(110～160℃),显示进入了成熟阶段。古近系定远组未进入成熟阶段,最大古地温出现在定远组沉积之后,但小于50℃。

Based on vitrinite reflectivity analysis, paleogeotemperature inversion and X ray diffraction series of the smallest granule illite crystallinity, this paper has analyzed thermal evolution of source rock since Carboniferous-Permian. The result indicates that 1 ： Carboniferous-Permian source rock was in high maturity, entered threshold of oil generation after the lower Jurassic deposition. After the upper Jurassic, paleogeotemperature was up to 245℃. 2： Fanghushan Formation of the lower Jurassic was also in higher maturity, entered threshold of oil generation after the middle Jurassic, maximal paleogeotemperature up to 260℃after the middle Cretaceous. 3 ： Middle-upper Jurassic en- ter threshold of oil generation at lower Cretaceous. Its maximal paleogeotemperature up to 225℃ and 230℃ after Zhuxiang Formation. 4 ： Maximal paleogeotemperature of Zhuxiang Formation up to 110-120℃ at the end of the early Cretaceous 5 ：. Dingyuan Formation of paleogene is immature, maximal paleogeotemperature less than 50℃ after Dingyuan Formation deposition.