鄂尔多斯盆地油气资源丰富的成因与赋存-成藏特点

Genesis of rich hydrocarbon resources and their occurrence and accumulation characteristics in the Ordos Basin

刘池洋 王建强 张东东 赵红格 赵俊峰 黄雷 王文青 秦阳

Chiyang Liu Jianqiang Wang Dongdong Zhang Hongge Zhao Junfeng Zhao Lei Huang Wenqing Wang Yang Qin

鄂尔多斯盆地油气发现早，至今油气勘探和开发仍方兴未艾。2020年产油气当量已超过7 900×10 t，位居中国诸含油气盆地之首。盆地油气资源丰富的成因和赋存-成藏特点，主要与以下4个特性有关：①盆地南部中生代延长期富烃坳陷形成于构造活动明显和深部作用活跃的动力环境中，具大型、伸展和热温特性，属后陆盆地原型；②现今盆地为中生代和晚、早古生代3个世代大型克拉通盆地复合叠加而成，为多重叠合盆地；③三叠系延长组优质烃源岩和石炭系-二叠系煤系烃源岩，均以富铀并夹多层凝灰岩为特色；④盆地后期遭受了多种形式边强内弱的改造，遂隆升为高原，属残留盆地。这4大具有鲜明个性的属性和特征，使盆地蕴藏有巨量油气资源，各世代盆地油气赋存-成藏各具特点、空间分区类型有别；常规与非常规油气在成藏和分布诸方面存在明显的时空过渡性和共存兼容性，多以垂向短距离运聚、近源成藏为特色；低渗-特低渗致密储层广布，油气藏主要为致密地层岩性油气藏，具低渗、低压、低产特征；盆地持续勘探潜力巨大、领域广阔。

Despite a long history of oil and gas exploration and production, the Ordos Basin is still a place full of surprises that attract numerous geologists and petroleum engineers.By the year of 2020, the basin has accumulatively produced more than 79 million tons of oil equivalent, ranking the first among all the petroliferous basins in China.This study relates the genesis, occurrence and accumulation characteristics of abundant hydrocarbons in the basin to four features that define it.①The hydrocarbon-rich sag in the southern basin during the deposition of the Yanchang Formation in Mesozoic is formed in a dynamic environment with obvious tectonic activities and active deep actions.The basin in that period belongs to a type of large-scale, extensional backland prototype basin against a favorable geothermal setting.②The basin at present is a multiple superimposed basin as a result of composite superimposition of three successive large cratonic basins during the Mesozoic, early-Paleozoic and late-Paleozoic, respectively.③High-quality Triassic Yanchang Formation source rocks and Carboniferous-Permian coal-measure source rocks are both rich in uranium and multiple interlayered tuffs.④During a late evolution, the basin, reshaped by various reformation featuring intense on borders and weak in interior, was uplifted into a plateau and eventually evolved into a residual basin.The above four distinctive attributes and characteristics work in unison in shaping the basin into a treasure house of hydrocarbons.The occurrence and accumulation of oil and gas in the basin of different periods have their own characteristics and spatial division types.Conventional and unconventional hydrocarbon resources also show obvious spatial-temporal transition and coexistence compatibility in terms of accumulation and distribution, which are characterized by vertical migration over short distances and near-source accumulation.Low-and ultra-low-permeability tight reservoirs are widespread and tight stratigraphic and lithological reservoirs with low permeability, low pressure, and low yield dominate.Based on the above analysis, it can be foreseen that the exploration potential of the basin is still huge and worthy of broader investigation.

10.11743/ogg20210501