Geological And Geochemical Characteristics And Hydrocarbon Generation Potential Of The Carboniferous Source Rocks In Santanghu Basin

In this paper,the source rocks of the Upper Carboniferous Haerjiawu and Kalagang formations in Santanghu Basin are taken as the main research objects.The Carboniferous crude oil was classified by the parameters which can reflecting the source material and formation environment,and the accuracy was verified by the cross plot of various parameters.Finally,comparing the source rocks with crude oil based on the characteristics of GC-MS and the biomarker parameters determine the effectiveness of main source rocks of Carboniferous.On the basis of lithology description and experimental analysis,combined with various logging curves,the lithology of the Carboniferous logging is corrected in more than 70 wells,and the thickness of the Carboniferous source rocks in wells is recalculated.Geochemical experiments such as pyrolysis,extraction and separation of organic matter,vitrinite reflectance measurement,X-ray diffraction and gas chromatographic analysis of saturated hydrocarbons have been carried out.To study and compare the differences of geochemical characteristics of source rocks from different stratas and lithologies in mineral composition,organic matter enrichment degree,parent material type,thermal evolution degree and biomarker compounds.The condition of source rocks formation environment of Haerjiawu Formation and Kalagang Formation has been determined by means of trace element geochemistry.It is found that there are three sets of source rocks developed in the Upper Carboniferous of Santanghu Basin can be used as effective source rocks.Among them,the organic matter abundance of the source rocks in the Harjiawu Formation is the highest,the lower is slightly higher than the upper,the carbonaceous mudstone is slightly higherthan the Tuffy mudstone.The organic matter abundance center of the Harjiawu Formation is concentrated in the Niudong 201-Ma33-Ma71 well area,and the parent material type is either type II₁ or II₂,which is in mature evolution as a whole.The maturity gradually increases from north to south and from east to west.Fromed in marshy lagoon environment with low salinity and weak oxidation-reduction.The organic matter abundance of source rocks in Kalagang Formation is low,and concentrates in Ma 33-Ma71 well area.The organic matter abundance is tuffaceous mudstone,dolomitic mudstone and deep gray mudstone from large to small,and the organic matter type is II₁ or II₂.,which is in immature stage,formed in a lake environment with high salinity and strong reductivity.Based on the above work,the main source rocks of Carboniferous in Santanghu Basin are finally determined to be carbonaceous mudstones and tuffaceous mudstones of Haerjiawu Formation,which lay a solid foundation for the next exploration of Carboniferous.