鄂尔多斯盆地塔巴庙地区上古生界源岩热演化特征

Thermal evolution characteristics of source rocks of the Upper Paleozoic in Tabamiao Block in Ordos Basin,China

鄂尔多斯盆地北部主力气源岩太原组、山西组煤系地层热成熟史的研究对本区天然气充注过程和有利目标区预测具有重要的参考价值。在对研究区烃源岩评价和一维、二维地质建模研究的基础上,利用BasinMod盆地模拟软件对单井以及研究区内二维剖面、平面进行了煤系烃源岩热演化史模拟研究。研究结果表明:(1)该区在中三叠世进入生烃门限,中侏罗世以后,烃源岩持续埋深,早白垩世末期至最大埋深(4000 m左右),绝大多数的天然气都在这一阶段生成,早白垩世末构造抬升以后只有少量天然气生成;(2)研究区上古生界太原组和山西组煤系源岩最大累积生烃强度可达到2200×108m3/km2,对现今天然气的分布具有较强的控制作用。

Coal formation of Taiyuan Formation and Shanxi Formation are source rocks in the northern part of Ordos Basin, and studying on its thermal maturity history is an important reference to forecast gas filling process and favorable target areas. On the basis of source rocks evaluation and 1D and 2D modeling of coal formation in the studying area, thermal evolution history modeling of source rocks in single well and 2D profile and plane of studying area was made using BasinMod software. The results showed that： source rocks entered into hydrocarbon generation threshold in Middle Triassic, continued to bury to the greatest depth （about 4 000 m） from Middle Jurassic to the late stage of Early Cretaceous, the vast majority of natural gas are generated at this stage,and only a small amount of natural gas produced after tectonic uplift of formation in the late stage of Early Cretaceous; cumulative hydrocarbon generation of Taiyuan Formation and Shanxi Formation reached 2 200×10^8m^3/km^2, which controlled present distribution of natural gas.