鄂尔多斯盆地热动力演化史及其对油气成藏与富集的控制作用

Thermodynamic evolution and hydrocarbon accumulation in the Ordos Basin

任战利 祁凯 李进步 霍小菊 崔军平 杨鹏 王琨 陈占军 杨桂林

Zhanli Ren Kai Qi Jinbu Li Xiaoju Huo Junping Cui Peng Yang Kun Wang Zhanjun Chen Guilin Yang

鄂尔多斯盆地热演化史及热岩石圈厚度恢复表明，中生代晚期早白垩世存在构造热事件及深部热岩石圈减薄的动力学过程，盆地南部岩石圈厚度薄，热流值及地温梯度高。不同层位烃源岩在盆地南部热演化程度高，热异常明显。烃源岩热模拟实验以及盆地深部热动力演化史研究表明，早白垩世热事件及形成的热异常使烃源岩生烃量明显增加，是盆地油气富集的重要原因之一。不同层位烃源岩在早白垩世大规模生油、生气及成藏，主要受早白垩世岩石圈减薄的深部热动力学过程及构造热事件控制。古生界和中生界不同层位的油气田分布主要受烃源岩、热演化程度及储层控制。从烃源岩发育层系及热演化程度来看，盆地南部延长组7段致密油、页岩油热演化程度高，分布面积广，勘探潜力巨大；石炭系-二叠系煤系烃源岩全盆地大面积分布，天然气勘探前景广阔；深层下古生界奥陶系碳酸盐岩层系具有形成大气田的条件，需要进一步明确烃源岩生烃潜力；深层中-新元古界值得进一步勘探，关键是明确规模断陷分布及烃源岩的生烃规模。

The thermal history and thermal lithospheric thickness restoration for the Ordos Basin indicate that tectonic thermal events and dynamic processes of deep thermal lithosphere thinning in the Early Cretaceous result in thin lithosphere, high heat flow values and geothermal gradient at the southern part of the basin.Source rocks at different horizons there also show high maturity and obvious thermal anomalies.Thermal simulation for the source rocks and thermodynamic history of the basin indicate strong influence of the thermal events and thermal anomalies in the Early Cretaceous on the significantly increasing amount of hydrocarbon generation, which is also interpreted to be one of the important reasons behind the high oil and gas enrichment in the basin.The large-scale hydrocarbon generation and accumulation from these source rocks in the Early Cretaceous are mainly controlled by the deep thermodynamic process of lithosphere thinning and tectonic thermal events during the period.The distribution of oil and gas fields in different Paleozoic and Mesozoic layers is mainly controlled by the distribution of source rocks and their thermal maturity as well as reservoirs.From the perspective of source rock development and thermal maturity, tight oil and shale oil in the Chang 7 member (Yanchang Formation) of southern basin have high thermal maturity, and are widely distributed, making the member a quite promising exploration target.The Carboniferous-Permian with its basin-wide occurring coal-measure source rocks has high exploration potential for natural gas.The deep Lower Paleozoic Ordovician carbonate sequences have the conditions favorable for large gas fields to form but further study is needed to clarify the hydrocarbon generation potential of source rocks.The deep Proterozoic is also worthy of an exploratory gaze with the distribution of fault depressions and the hydrocarbon generation capacity of source rocks being recommended as the focuses.

10.11743/ogg20210502