The Research On The Distribution Of Upper Paleozoic Source Rock In The South Of North China Basin

The upper Paleozoic sedimentary strata in the southern part of North China Basin are mainly coal-bearing strata.Source rocks are mainly developed in three types: carbonate rocks,dark mudstone and coal rocks.In this paper,the Paleozoic coal-bearing sedimentary strata in the southern part of North China Basin are studied as the research subjects,and four typical areas(Luoyang Region,Yuzhou Region,Ping Dingshan Region and Yongcheng Region)are selected as the key anatomical regions.By careful observation of the surface outcrop and all core drillings of four typical regions,combinating with rock slice observation and analysis of XRD,particle size,organic geochemistry and well logging curves.Furthemore,under the guidance of the high resolution sequence stratigraphy,establishing high-resolution sequence stratigraphic framework in research region to discuss vertical and lateral distribution of the upper Paleozoic source rocks and the development of favorable area on the plane.The comprehensive analysis showed that the coal-bearing strata are developed on the basis of the unified Late Paleozoic epicontinental basin of North China Basin.Benxi Formation,Taiyuan Formation and under the mainly coal-bedding of Shanxi Formation are mainly develop barrier-free clastic and tidal flat sedimentology system,the Upper Shanxi Formation and Upper,Lower Shihezi Formation are mainly develop delta system affected by indirect transgressions.The Benxi Formation,Taiyuan Formation,Shanxi Formation and Upper,Lower Shihezi Formation of the upper Paleozoic in the southern part of North China Basin can be unified classificating into two super long-term and eight long-term stratigraphic base-level circles.The results show that the Upper Paleozoic sedimentary strata in the southern part of North China Basin indicate a regression sequence on the whole,the super-long-term stratigraphic base-level circles are all whole transgressive-regressive cycles and the long-term stratigraphic base-level circles are often show characteristics of fast transgression and slow regression.On the basis of testing the TOC(Total Organic Carbon)content of the whole core drilling hole,putting the test results into the isochronal high-resolution stratigraphic sequence framework,combined with the change of depositional environment,the following conclusions can be drawn by this paper:(1)In the vertical direction,it is the most favorable period of the hydrocarbon source rocks that is in the middle and late stages of the rising half cycle of the Super long-term stratigraphic base-level circle and the late stage of the rising half cycle and the early stage of descending half cycle of the long-term stratigraphic base-level circle.There be high abundance of organic matter in the hydrocarbon source rocks in the vicinities of base level rotation represent by the mudstone rocks and coal rocks of tidal flat facies,diversion bay facies and swamp facies.The favorable hydrocarbon source rocks is mainly developed in the lower part and the upper part is only locally developed.(2)In the horizontal direction,the thickness of source rocks in the South East is relatively large,It shows that the whole late Paleozoic sedimentary period is in the background of water retreat,the sea water is gradually receding Probably to the south and the East;In the direction of water receded,hydrocarbon source rocks of the sequence increase gradually and also show a strong heterogeneity in the horizontal direction,favorable hydrocarbon source rocks of the long-term base level cycle sequence number and thickness increase gradually in the overall direction of regression,which reflects the characteristics of transgression frequency difference on the plane.(3)The variation law of hydrocarbon source rocks in the horizontal and vertical is summarized:The development of favorable hydrocarbon source rocks of Upper Paleozoic coal bearing strata in the southern part of North China Basin is closely related to transgression,The transgression fundamentally restricts the development of favorable hydrocarbon source rock;On the whole,the favorable source rocks of the upper Paleozoic in the southern part of North China Basin are thicker to the south and east.