Organic Petrology Study on the Yan'an Formation Coal Measures in Ordos Basin

YAO Su ping; ZHANG Jing rong; WANG Ke ren; LUAN Qin

It is still a disputing problem whether the Jurassic coal measure are the another oil source rock or not.Some coal petrologists believe that there may be oils from coal based on the higher content of liptinites contained in it.Others don't agree because the chemical structure of crude oils can't be related to maceral composition dominated by liptinites from coals. In this paper, the three sites,respectively Lingwu-yanchi area lying in the northern basin,Longdong area in the middle basin and HuanLing-Tongchuan area in the southern basin,are selected to collect coal samples. The coal macrotype,microtype,macerals and their oil-generating potential are studied in detail and then discussed.The research results indicate that the principal macerals are vitrinite and inertinite in the coal of Yan'an Formation,and the coal contains liptinites less than 5% and it's petroleum potential will be very low when it only depends on the minor content of liptinites it contains.Thus,it is very important if vitrinite group became oil-pron macerals,especially desmocollinite.The desmocollinites can be drvided into three subtypes A, B and C according to the genesis and hydrocarbon-generating nature,only desmocollinite B and C have moderate to high petroleum potential,whereas desmocollinite A is not oil-prone maceral which is the main type in desmocollinite.In general,the coal of Yan'an Formation is of poor petroleum potential.However,the cannel coal and bright coal contain the large amount of sporinites in the middle and south of the basin,where content the sporinites is about 10%,the maximum oil-generated period of sporinite corresponds to 0.9%～1.1% vitrinite reflectance,whereas above coal reflectance is only 0.6%～0.7% and bright coal volume is less than 2% in all coals.The cannel coals and bright coals may generate minor amount oil.So the Yan'an Formation coal measure can't become the commercial oils source rocks in Ordos basin.

1. Department of Earth Sciences, Nanjing University,Nanfing 210093

Received Date: 1998-03-04

Publish Date: 1999-06-10

Key words:

organic /
petrology /
oils

Abstract: It is still a disputing problem whether the Jurassic coal measure are the another oil source rock or not.Some coal petrologists believe that there may be oils from coal based on the higher content of liptinites contained in it.Others don't agree because the chemical structure of crude oils can't be related to maceral composition dominated by liptinites from coals. In this paper, the three sites,respectively Lingwu-yanchi area lying in the northern basin,Longdong area in the middle basin and HuanLing-Tongchuan area in the southern basin,are selected to collect coal samples. The coal macrotype,microtype,macerals and their oil-generating potential are studied in detail and then discussed.The research results indicate that the principal macerals are vitrinite and inertinite in the coal of Yan'an Formation,and the coal contains liptinites less than 5% and it's petroleum potential will be very low when it only depends on the minor content of liptinites it contains.Thus,it is very important if vitrinite group became oil-pron macerals,especially desmocollinite.The desmocollinites can be drvided into three subtypes A, B and C according to the genesis and hydrocarbon-generating nature,only desmocollinite B and C have moderate to high petroleum potential,whereas desmocollinite A is not oil-prone maceral which is the main type in desmocollinite.In general,the coal of Yan'an Formation is of poor petroleum potential.However,the cannel coal and bright coal contain the large amount of sporinites in the middle and south of the basin,where content the sporinites is about 10%,the maximum oil-generated period of sporinite corresponds to 0.9%～1.1% vitrinite reflectance,whereas above coal reflectance is only 0.6%～0.7% and bright coal volume is less than 2% in all coals.The cannel coals and bright coals may generate minor amount oil.So the Yan'an Formation coal measure can't become the commercial oils source rocks in Ordos basin.

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Reference (12)

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Organic Petrology Study on the Yan'an Formation Coal Measures in Ordos Basin

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