The Sinian Stratigraphic Sequences And Petroleum Geology In Yalu River Basin

The Yalu River Basin is distributed in Baishan,Songshu Town and Linjiang Area in southern Jilin Province.Based on the Sinian data exposed in the Yalu River basin and the core data of the Songdi 4 well in the Jilin oilfield,the author determined the strata sequences of the Sinian in the Yalu River basin and correlated the two sequences.Based on the characteristics of lithologic changes in the Songdi 4 Well and combined with the characteristics of outcrop lithology in the field,the sedimentary facies identification method was used to identify the type of sedimentary facies and the sedimentary facies model of Songdi 4 Well.By analyzing the distribution of field strata and combining the vertical development characteristics revealed by geological drilling,a tectonic evolutionary model of the Yalu River Basin was established to reveal the structural characteristics of the basin.On this basis,the Yalu River basin was divided into 4 primary structural units and 11 Secondary structural units.Through the evaluation of the Sinian source rocks in the well Songdi 4 in the Yalu River Basin,the results show that the basin has a certain exploration potential,and then determine favorable exploration zones in the basin.The Sinian stratigraphic sequences of the Yalu River Basin were divided into the Wanlong Formation,the Badaojiang Formation and the Qinggouzi Formation.The Wanlong formation of the lower Sinian is a set of marine carbonate rocks,whose lithology is dominated by wormlike limestone,gray limestone and dolomitic limestone,with shale intercalation,and this group is characterized by a significant vermicular structure in the limestone.The Badaojiang formation of the middle Sinian is also a set of marine carbonate rocks,whose lithology is dominated by stromatolitic limestone,and this group is characterized by stromatolitic limestone.The Qinggouzi formation of the upper Sinian is shale in shallow water environment,and its lithology is mainly black shale and gray limestone.This group is characterized by the development of obvious black shale formation.The Sinian of the Songdi 4 well in the the Yalu River basin is the platform facies.It can be divided into 3 subfacies: open platform,local platform and tidal flat.The Wanlong formation is mainly the open platform subfacies.The Qinggouzi formation is mainly local platform subfacies.The Badaojiang formation is mainly the tidal flat subfacies,it can be divided into intertidal microfacies.The Yalu River Basin is formed by the uncoordinated overlap of Neoproterozoic-Paleozoic Craton internal down-warped basin and Mesozoic upper continental rift and fault basin.The first-level tectonic units of the basin include the western downfaulted zone,the eastern downfaulted zone,the Hunjiang-Songshuzhen synclinorium,and the Yalu River north bank syncline.The sub-tectonic units of the basin include Guosong fault depression,Liudaojiang fault depression,Shiren fault depression,Fusong fault depression,Yihe fault depression,Sidaogou fault depression,Maanshan fault depression,Hunjiang syncline,Dayangcha hemi syncline,Wangou syncline and Songshu town syncline.The test data of the Sinian source rocks in Sogdi 4 well of the Yalu River basin show that the abundance of organic matter of the limestone source rocks in the Wanlong formation and the Badaojiang formation is better,the type of organic matter is type II and the maturity of the source rock is mostly in the mature stage.The source rocks of Qinggouzi formation are mainly black shale,the abundance of organic matter of the source rocks is poor,the type of organic matter is type II,and the maturity of the source rock is mostly in the low mature and mature stage.The fractured carbonate rocks are good reservoirs of Sinian,and the reservoir properties are characterized by extremely low porosity and ultra-low porosity.The source-reservoir-cap assemblage is mainly composed of self-generation and self-reservoir,upper-generation and lower-reservoir,lower-generation and upper-reservoir.Comprehensive analysis of the structural characteristics of the study area and the Sinian source rock evaluation results confirm that the favorable exploration zones of the Sinian oil and gas in the study area are mainly distributed in the mid-deep layer of syncline in the Songshu town,the northwest wing of the Wangou syncline,and the deep layer of the Hunjiang syncline core and its northwest wing.