Sedimentation And Geochemistry Of Potential Source Rocks In Pt_2-3-?₁ Around Ordos Region

With the discovery of original oil and gas resources from the Middle-Upper Proterozoic to Lower Cambrian around the world,the source rocks have become the research object with great attention.The Middle-Upper Proterozoic to Lower Cambrian strata with rich organic matter have been discovered in the Ordos surrounding areas.However,whether they are oil and gas source rocks? Whether they are distributed in the Ordos basin? This requires basic research.This paper focuses on development characteristics of the Middle-Upper Proterozoic to Lower Cambrian potential source rocks in the Ordos surrounding areas,including lithology and lithologic association characteristics and sedimentary environment.Also to study the geochemical characteristics combining trace and ree elements,residual organic carbon and pyrolysis experiments.Furthermore,compare comprehensively different potential source rocks in different areas.Finaly,explore the possibility of their distribution in the basin and hydrocarbon potential.The ultimate goal is to provide the basis for further research.Through exploring seven field sections in the western part of inner mongolia outside the northern margin of the basin and laboratory analysis,it is discovered that the black carbonaceous slate in Agulugou formation of Zhaertaishan group of Changchengian system is potential high-quality source rocks whose residual TOC can reach 12.81%,which was deposited in deep water trough.We find that the black carbonaceous phyllite in Baishugou formation and “bone coal” in Meiyaogou formation of Qingbaikouan system is also potential high-quality source rocks with highest residual TOC(38.02%),which are deposited in the bay and lagoon environment with occluded water,through exploring twelve field sections in Luanchuan area outside the southern margin of the basin and laboratory analysis.The black shale in Gaoshanghe formation of Changchengian system in Xunjian town,Luonan county and the black carbonaceous shale in Sandaozhuang formation of Lower Cambrian in Jingcun town are potential good source rocks whose residual TOC can reach 1.52%,which have also gas generating potential.After the survey of the mudstone in Zhengmuguan formation of Sinian and the carbonate in Suyukou formation and Wudaotang formation of Lower Cambrian in Suyukou field section in the western margin of the basin,we did not find potential source rocks,because their residual TOC is less than 0.1%.Through the analysis of the lithofacies palaeogeography and possible hydrocarbon generation history of the Middle-Upper Proterozoic to Lower Cambrian strata in the Ordos Basin,we discover that sediments almost deposited in all Ordos Basin and an inland rift has developed during the Changchengian Period.Therefore,similar source rocks found outside the north of the basin should be have deposited which may be in the high mature stage at present and can generate a large number of natural gas.As a consequence,the direction of exploration should be along the rift extension.