Characteristics and exploration directions of inner gas source from the middle assemblage of Ordovician in Ordos Basin

被引：0
|
作者：
Xu W. [1 ]
Hu S. [1 ]
Li N. [1 ]
Wei X. [2 ]
Gao J. [1 ]
Zhao Z. [1 ]
Li X. [3 ]
Liu J. [1 ]
Zhang Y. [1 ]
Song W. [1 ]
机构：
[1] PetroChina Research Institute of Petroleum Exploration & Development, Beijing
[2] Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi'an, 710018, Shaanxi
[3] PetroChina Research Institute of Petroleum Exploration & Development-Northwest, Lanzhou, 730020, Gansu
来源：
Shiyou Xuebao/Acta Petrolei Sinica | 2019年 / 40卷 / 08期
关键词：
Crude oil cracking gas; Gypsum-salt rock; Hydrocarbon source rock; Natural gas isotope; Ordos Basin; Ordovician;
D O I：
10.7623/syxb201908002
中图分类号：
学科分类号：
摘要：
Majiagou Formation of the Lower Paleozoic in Ordos Basin is divided into three assemblages by the degree of exploration: the upper, middle and lower assemblage, respectively corresponding to the 1-4 sub-members of the 5th Member of Majiagou Formation(the upper assemblage), the 5-10 sub-members of the 5th Member of Majiagou Formation(the middle assemblage) and the 4th to the 1st Member of Majiagou Formation(the bottom assemblage). To explore the characteristics of natural gas source in the middle assemblage, this study carries out natural gas genetic identification, source rock evaluation and researches on the natural gas components, isotopes and fluid inclusions, as well as a comparative analysis with natural gas in the Upper Paleozoic and Ordovician weathering crust. The results show that: (1) In terms of composition characteristics and isotopic characteristics, the inner-type natural gas in the middle assemblage of Ordovician is different from the natural gas in the Upper Paleozoic Carboniferous-Permian and weathering crust. Through identifying based on the natural gas component data and previous experimental plates, it is believed that crude oil cracking gas exists in the internally- developed natural gas from the Ordovician middle assemblage. (2) The bitumen internally developed in the Ordovician is the thermal cracking product of liquid hydrocarbons formed in the inner source rocks. (3) Controlled by the tidal flat sedimentary system, the typical source rock stratum of the middle assemblage (the 6th sub-member of the 5th Member of Majiagou Formation) can be divided into three facies belts: argillaceous dolomitic flat belt, gypsum-containing slope, and gypsum-salt depression. (4) Source rocks in the 6th sub-member of the 5th Member of Majiagou Formation are mainly distributed in the argillaceous dolomitic flat belt, with a cumulative thickness of 8-20 m; the organic matter abundance is up to 1.75%, and Ro is 1.9%-2.7%. In the stage of thermal cracking and generation, there is a potential for hydrocarbon supply in a large scale. (5) The argillaceous dolomitic flat belt and gypsum-containing slope indicate the favorable exploration direction, and the eastern part of Wushenqi, northwest of Jingbian and Wuqi-Zhitan area are three favorable exploration zones. © 2019, Editorial Office of ACTA PETROLEI SINICA. All right reserved.
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页码：900 / 913
页数：13
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