查干凹陷中、新生代热史及烃源岩热演化

查干凹陷是内蒙古银-额盆地最具勘探潜力的凹陷, 为了揭示查干凹陷中、新生代热史及烃源岩热演化历史, 首先利用9口井的镜质体反射率数据恢复了查干凹陷中、新生代热史, 结果显示查干凹陷在早白垩世巴音戈壁组沉积开始至银根组沉积末期, 地温梯度逐渐增加, 且到银根组沉积末期达到最大, 为50~58 ℃/km; 自晚白垩世乌兰苏海组沉积开始至今, 地温梯度逐渐下降, 现今地温梯度仅为31~34 ℃/km.再以热史为基础, 结合沉积和构造发育史及烃源岩地球化学资料, 模拟了查干凹陷9口井3套烃源岩的成熟度演化历史, 模拟结果显示查干凹陷烃源岩成熟度演化受古地温控制, 3套烃源岩成熟度都在早白垩世晚期达到最大. 

Mesozoic and Cenozoic Thermal History and Source Rock Thermal Evolution History in the Chagan Sag, Inner Mongolia

The Chagan sag has the greatest potential for oil and gas exploration among other sags in the Yin'gen-Ejinaqi basin. To reveal the Mesozoic and Cenozoic thermal history and source rock thermal evolution history in the Chagan sag, the thermal history was modeled on basis of vitrinite reflectance data of 9 wells. The modeled results show the thermal gradients increased gradually from the Early Cretaceous Bayin'gebi Formation to the end of the Yin'gen Formation, and the thermal gradients reached maximum values(50-58 ℃/km) at the end of the Yingen Formation.Then the thermal gradients decreased gradually from the Late Cretaceous Wulansuhai Formation to the present day, and the thermal gradients is only 31-34 ℃/km in the present day. Meanwhile, based on the above thermal gradient data, with combination of the depositional and tectonic development history and geochemical parameters of source rocks, maturation histories of 3 sets of source rocks of 9 wells were modeled. The modeled results show the maturation histories were controlled by the palaeogeothermal, and the maturation of 3 sets of source rocks reached maximum values in the late period of the Early Cretaceous.