| The study area is located in the southern part of the Songliao Basin.It is located in Jilin Province and contains abundant oil shale resources.It is mainly developed in the section of the Qingshankou Formation and the first and second sections of the Nenjiang Formation of the Upper Cretaceous.Previously,oil shale in this area was evaluated for oil shale ground retorting technology,and oil shale geological evaluation for in-situ mining technology was lacking.Therefore,by studying the geological characteristics of each oil shale deposit in this area and analyzing the geological factors affecting the in-situ exploitation of oil shale,this paper makes a preliminary geological evaluation of in-situ exploitation of oil shale in this area,which provides a scientific basis for in-situ development of oil shale in this area.In this paper,through the section survey,core observation and log analysis,it is believed that the Qingshankou Formation and the Nenjiang Formation of the study area mainly develop three sedimentary facies of delta,lake and lake bottom fan.It is further divided into four sub-phases and eight micro-facies,such as delta front,shallow lake,semi-deep lake-deep lake and outer fan.The oil shale is mainly distributed in the semi-deep lake-deep lake environment.There are 12 oil shales in the Qingshankou Formation and 6 oil shales in the first and second sections of the Nenjiang Formation.Among them,Qingshankou Formation QS3,QS4 and Nenjiang Formation NJ5 oil shale are the best ore layers,showing a stable layered distribution in the whole area,with a buried depth of 0-1200m.The average oil content of oil shale in QS3,QS4and NJ5 reservoirs is 5.8%,5.1%and 4.8%respectively.The organic matter type is mainly type I,followed by type II,which is in the stage of immature and low maturity evolution.It is medium-low quality,high ash content,medium calorific value and ultra-low sulfur oil shale.The oil shale of Qingshankou Formation and Nenjiang Formation in the study area has the characteristics of high natural gamma ray,high resistivity,high acoustic time difference and low density logging response,and the correlation between organic carbon and resistivity and density logging curves is the best.Based on the experimental results of organic carbon,the△logR model of oil shale of Qingshankou Formation in the study area is established.The results are reasonable and the continuous values of organic carbon of oil shale can be obtained.In this paper,the oil shale in the study area was evaluated according to different horizons and different depths of the same horizon.The results show that the QS3,QS4 in the Qingshankou Formation and NJ5 in the Nenjiang Formation have the most oil shale resources.Among them,QS3 oil shale resources are 1422775.01×10~4tons;QS4 oil shale resources are 1410644.28×10~4tons;NJ5 oil shale resources are 3260832.45×10~4tons.The resources were further evaluated at different depths of 0-100m,100-300m,300-500m,and 500-1000m.Finally,by analyzing the in-situ geological parameters of oil shale,it is considered that the QS3 and the QS4 ore of Qingshankou Formation and NJ5 of Nenjiang Formation in the study area are favorable for oil shale in situ mining.And through the four indicators of oil content,thickness,resource abundance and area,four favorable target areas suitable for oil shale in situ mining are selected in the favorable layer.Among them,the I selected area of QS3 ore of Qingshankou Formation is most suitable for oil shale in situ mining,followed by I selected area of QS4 ore of Qingshankou Formation,and I selected area andⅡselected area of NJ5 of Nenjiang Formation. |
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