Discovery, characteristics and resource potential of continental tight oil in Triassic Yanchang Formation, Ordos Basin

doi:10.3969/j.issn.1672-7703.2017.06.002

Abstract

Abstract: The first commercial tight oil field in continental facies in the world was discovered in the Upper Triassic Yanchang Formation of the Ordos Basin in central China. Different from other liquid hydrocarbons found in marine shale systems in North America, tight oil reservoirs in the Ordos Basin are lacustrine deposits where the tight oil is mainly preserved in tight sandstones in the middle-upper seventh member of the Yanchang Formation (Chang 7 Member) in a lacustrine basin, and characterized by overlapped sand bodies (20-70 m thick), tightness (with porosity of 6%-12%, permeability <0.3mD), high brittle mineral content (70%-80%), high crude oil saturation (60%-80%), high crude oil quality (in-place oil density of 0.70-0.75 g/cm³), low formation pressure (pressure coefficient between 0.6-0.8), low production (several tons to more than ten tons per well per day), and extensive and continuous distribution (3×10⁴km²). Based on the geological and drilling data of the tight oil in the Chang 7 Member of the Ordos Basin, and using the "sweet spots prediction method", this paper calculates that the in-place petroleum resources is 42.26×10⁸t, the average resource abundance is 15×10⁴t/km², and the distribution area is 2.9×10⁴km² in the Chang 7 Member. The discovery and overall development of the first continental tight oil field is of great importance for large-scale exploitation of lowquality tight oil resources in similar continental depression basins.

Key words: continental tight oil, continuous petroleum accumulation, evaluation of sweet spot region, resource potential, shale oil

CLC Number:

TE122.2

Yang Zhi, Fu Jinhua, Guo Qiulin, Lin Senhu, Chen Ningsheng, Pan Songqi, Li Shixiang. Discovery, characteristics and resource potential of continental tight oil in Triassic Yanchang Formation, Ordos Basin[J]. China Petroleum Exploration, 2017, 22(6): 9-15.

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