冀中坳陷苏桥-文安油气田混源油定量识别模式研究(一):原油成因分类及地球化学特征

通过对原油的族组成、碳同位素、饱和烃和芳烃地球化学特征的剖析,查明苏桥-文安地区原油中不仅存在煤成油,而且存在由煤成油与下第三系原油混合而成的混源油。煤成油表现出饱和烃含量极其丰富、Pr/Ph值高(大于2)、三环萜烷以低碳数(C19～C21)化合物占优势并有递减变化趋势、C24四环萜烷丰富和伽马蜡烷含量低等地球化学特征。下第三系原油与煤成油的地球化学特征恰恰相反,Pr/Ph值低(小于1)、低碳数三环萜烷含量低并有递增变化趋势、C24四环萜烷的含量不高和伽马蜡烷含量相对丰富。混源油的地球化学特征介于煤成油与下第三系原油之间,但参数值受控于端元油混入的绝对含量。在以上地球化学特征基础上提出了冀中坳陷煤成油、下第三系油和混源油的识别指标。

STUDY ON QUANTITATIVE IDENTIFICATION MODEL OF MIXED OILS FROM SUQIAO -WENAN AREA IN JIZHONG DEPRESSION PART I:GENETIC-TYPES AND GEOCHEMICAL CHARACTERISTICS OF CRUDE OILS

Geochemical characteristics of crude oils of Suqiao-Wenan and Chaheji area in Jizhong depression have been analyzed and studied systematically by various of geochemical techniques and methods for molecular information, the results suggest these crude oils can be fall into three groups of coal-formed oil, Paleocene Tertiary oil and mixed oil. The characteristics of coal-formed oil in Suqiao-Wenan are that saturated hydrocarbons amounts to about 80% of the bulk composition and Pristane/Phytane ratios more than 2.0, the contents of tricyclic terpanes with low carbon number(C_(19)-C_(21)) and C_(24) tetracyclic terpane are abundant, but gammacerane indices is low. In contrast, characteristics of Paleocene Tertiary oils in Chaheji area in Jizhong depression are that pristane/phytane ratio is low, contents of tricyclic terpanes with higher carbon numbers(C_(23)-C_(24)) are abundant, but the gammacerane amount is abundant. However, geochemical characteristics of mixed oils from Suqiao-Wenan area in Jizhong depression are between coal-formed oils in Suqiao-Wenan area and Paleocene Tertiary oils in Chaheji area.