Differences of formation environment and hydrocarbon generation characteristics between oil shale and mudstone in the second Member of Liushagang Formation in Weixinan sag
The oil shale and mudstone in the second Member of the Eocene Liushagang Formation(the Liu-2 Member for short)are the main Paleogene source rocks in Weixinan sag,so the study of the differences in their formation environment and hydrocarbon generation characteristics is of great significance for predicting high-quality source rocks and evaluating depressions in the new area of the Beibuwan basin.According to the principles and methods of organic geochemistry,element geochemistry and organic petrology,this paper compared the differences in formation environment and hydrocarbon generation characteristics between the two types of source rocks on the basis of geochemical characteristics comprehensive analysis of source rocks and laboratory simulation research.The results show that the Liu-2 Member oil shale corresponds to excellent source rocks with higher organic matter abundance and better kerogen types;the mudstone in this member are evaluated as good source rocks.These differences in geochemical characteristics and organic matter enrichment between oil shale and mudstone of the study area are comprehensively affected by parent rock properties,source compositions,palaeoproductivity and organic matter preservation conditions.The palaeoproductivity was higher and algae bloomed during the oil shale sedimentary period,and it is mainly deposited under reducing environment,which is conducive to the preservation of organic matter.While during the mudstone sedimentary period,the weakly reducing environment,fast sedimentation rate and extensive input of terrestrial materials are not conducive to the preservation of organic matter.The differences in kinetic characteristics and evolution patterns of hydrocarbon generation between oil shale and mudstone of the study area are affected by organic matter types and source compositions.Among them,the activation energy distribution of oil shale is relatively concentrated,while that of mudstone is relatively dispersed.The peak oil generation of oil shale occurs earlier than that of mudstone,and the oil yields of oil shale during the peak oil generation period are significantly higher than that of mudstone.
NETL
NSTL
万方数据
