Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (5): 1011-1029.doi: 10.11743/ogg20210501

• Petroleum Geology • Previous Articles     Next Articles

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

Chiyang Liu1,2(), Jianqiang Wang1,2, Dongdong Zhang1,2, Hongge Zhao1,2, Junfeng Zhao1,2, Lei Huang1,2, Wenqing Wang1,2, Yang Qin1,2   

  1. 1. State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, Shaanxi 710069, China
    2. Institute of Oil and Gas Basin, Northwest University, Xi'an, Shaanxi 710069, China
  • Received:2021-07-27 Online:2021-10-28 Published:2021-10-26

Abstract:

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.

Key words: genesis of rich hydrocarbon resources, uranium-rich source rock, Yanchang Formation, backland basin, multiple superimposed basin, residual basin, Ordos Basin

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