Evaluation Of Chang 7 Source Rock In Wuqi Area

The Wuqi area in the study area is located in the middle west of the Yishan slope of the secondary tectonic unit of the Ordos basin,including Zhifang,Maying,Youfangzhuang and other areas.The Chang7 hydrocarbon source rocks in the Ordos basin are relatively developed,and the area has excellent reservoir forming conditions.However,there are many basic geological problems that need to be solved urgently for the Chang7 oil reservoir group hydrocarbon source rocks.Through field geological exploration and the collation and study of relevant drilling data,it is identified that the Chang 7 oil layer formation in Wuqi area mainly develops two sedimentary facies,namely delta and lake,three subfacies,and seven sedimentary microfacies.Using logging data and other information,throughΔlgR method improved by normalization,according to the division of different zones,the evaluation model of organic carbon in source rocks is established.Comparing the calculated TOC value with the measured TOC value,it is found that the fitting degree is high,and using the calculated TOC value to draw TOC plane distribution maps for different horizons,laying a foundation for subsequent high-quality hydrocarbon source rock evaluation.Dark mudstone is developed in the study area.Based on core observation,the boundary between mudstone and non mudstone is determined to be 70%by logging methods.The thickness of mudstone in Chang7 group of the study area is calculated and contour maps of mudstone thickness at different layers are drawn.The basic geochemical characteristics of hydrocarbon source rocks in Wuqi area were studied using geochemical methods such as pyrolysis parameter analysis and kerogen microscopic analysis.It is found that the abundance of organic matter in source rocks is high,and the types of organic matter in source rocks are Type Ⅱ₁and Type Ⅱ₂.The maturity of organic matter in source rocks is high.Through comparative analysis,with TOC>2.0%,S1+S2≥20mg/g,and chloroform asphalt"A"content≥0.2%as the main reference parameters,the evaluation criteria for high-quality hydrocarbon source rocks in the study area have been established,and the distribution characteristics of high-quality hydrocarbon source rocks in each layer have been discussed.The high-quality source rock of Chang 7₂has the thickest thickness and the widest distribution,followed by Chang 7₃and Chang 7₁.Based on the analysis of hydrocarbon generation and expulsion characteristics in the study area,the resource amount of each layer and block in the study area is calculated,and the distribution map of hydrocarbon generation intensity at different layers is drawn,so as to optimize the favorable exploration target areas of Class Ⅰ and Ⅱ in the study area.