Main Controlling Factors and Genetic Types of Carbon Isotopic Compositions for Crude Oils from the Qaidam Basin, China

DUAN Yi; PENG De-hua; ZHANG Xiao-bao; Zhou Shi-xin; WANG Zhi-ping; ZHANG Hui

A suite of 40 crude oil samples from 16 oil fields in the Qaidam basin were analyzed using IRMS, and features, main controlling factors and genetic types of carbon isotopic compositions for these crude oils were studied. The results show that differences in carbon isotopic compositions between the western Qaidam crude oils and the northen Qaidam crude ouils are evident. The western Qaidam crude oils are enriched in ¹³ C,while the northern Qaidam crude oils are enriched in ¹² C. One finding is that carbon isotopic compositions of the western Qaidam curde oils from saline-hypersaline lacustrine environment are controlled mainly by oil-formed environments (e.g. salinity and humidity) and carbon isotopic compositions of the northern Qaidam crude oils from freshwater swampy-lacustrine environment rely mainly on their source natures. On the basis of their carbon isotopic compositions and Pr/Ph ratios,these oils could be divided into five genetic groups.

Main Controlling Factors and Genetic Types of Carbon Isotopic Compositions for Crude Oils from the Qaidam Basin, China

1. Lanzhou Institute of Geology,Chinese Academy of Sciences,Lanzhou 730000;

2. Lanzhou University,Lanzhou 730000;

3. Research Institute of Exploration and Development of Qinghai Oil Field Compamy,Dunhang Gansu 738600;

4. Plant Institute, Chinese Academy of Sciences, Beijing 100093

Received Date: 2002-07-05

Publish Date: 2003-06-10

Key words:

Abstract: A suite of 40 crude oil samples from 16 oil fields in the Qaidam basin were analyzed using IRMS, and features, main controlling factors and genetic types of carbon isotopic compositions for these crude oils were studied. The results show that differences in carbon isotopic compositions between the western Qaidam crude oils and the northen Qaidam crude ouils are evident. The western Qaidam crude oils are enriched in ¹³ C,while the northern Qaidam crude oils are enriched in ¹² C. One finding is that carbon isotopic compositions of the western Qaidam curde oils from saline-hypersaline lacustrine environment are controlled mainly by oil-formed environments (e.g. salinity and humidity) and carbon isotopic compositions of the northern Qaidam crude oils from freshwater swampy-lacustrine environment rely mainly on their source natures. On the basis of their carbon isotopic compositions and Pr/Ph ratios,these oils could be divided into five genetic groups.

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Reference (14)

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Main Controlling Factors and Genetic Types of Carbon Isotopic Compositions for Crude Oils from the Qaidam Basin, China

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