Oil Shale Characteristics And Metallogenic Conditions Of The Bayingebi Formation In The Lower Cretaceous In The Northeastern Margin Of Yin'e Basin

The study area is the Bagemaode oil shale mining area,which including the Huheqiabu exploration area.Bagemaode exploration area and Chagantaohaiaobaodong exploration area)in the northeast margin of Yin'e basin.There are abundant and relatively large oil shale,and the oil shale mainly occurs in the lower cretaceous Bayingebi formation.Based on field exploration,core observation,borehole data and a large number of relevant test data.This paper studies the characteristics of oil shale and organic matter enrichment of the target horizon in the mining area,and discusses the main factors of oil shale mineralization.According to the observation and test results of the open pit and core of oil shale,The average oil content of oil shale in the Bayingebi formation is 5.83%,the average ash content is 76.55%,and the average calorific value is 3.65MJ/kg,which is a medium ash and low-calorific oil shale of medium quality.The TOC content in oil shale is relatively high and has a high linear correlation with oil content,ash volatiles and calorific value.The mineral composition of oil shale and surrounding rock in oil-bearing shale section is mainly composed of terrigenous clastics with quartz as the main component and clay minerals with illite and i'meng mixed layers as the main component.TOC content with pyrolysis parameters can be used in the reaction of organic matter type and hydrocarbon generation potential of oil shale.The main hydrocarbon source rocks such as comparative study of the shale,oil shale has the highest degree of organic matter enrichment.There are?₁ and?₂ organic matter since is the result of lower aquatic organisms such as bacteria and algae.They are immature and low mature stage,and hydrocarbon generation potential is extremely good.Bayingebi formation mainly developed fan delta facies and lake facies,further divided into 4 types of subfacies and 7 kinds of microfacies.In the open shale pit and the core,there are a large number of leaf segments interface fossils,suggests that the lake deposition during the period of thriving.In addition,also identify marked by ostracod layer ostracod rapidly event deposits.Bayingebi formation was divided into four system domains,namely LST,TST,HST and RST.The LST stage was dominated by the fan delta plain and the front subfacies.The TST stage was dominated by the shallow lake and the semi-deep lake subfacies.The HST stage was dominated by the semi-deep lake and the deep lake subfacies.And the RST stage was dominated by the shallow lake and the water-entering delta facies.According to the geochemical parameter analysis of oil shale Rb/Sr,Sr/Cu,V/?V+Ni?,Ni/Co,Cu/Zn and other characteristics,the sedimentary period of the oil-bearing shale system was a hot and dry climate environment with alternation of semi-warm and semi-humid and a strong reducing water environment with alternation of semi-salty water and salty water.Oil shale can be formed in warm and humid freshwater-brackish water environment and hot and arid saline water environment,in which hot and arid saline water environment is conducive to the enrichment of organic matter and the formation of high-quality oil shale.Oil shale in the study area is mainly development in sequence of TST,HST,TST and HST early development the first?seam shale,formed in the great lakes near the surface,thickness of oil shale is relatively thin,oil content between 3.5⁵.8%,HST early development of the first?seam shale oil rate is between 3.5⁸.3%,oil content variation is smaller.HST during the middle-late development the first?seam and?seam shale and shale with a thickness is larger and stable,the first?seam shale oil rate is between 3.9¹0.0%,the first?seam shale oil rate is between 3.8¹0.3%,the oil content varies greatly.Hot-arid and semi-warm and semi-humid climatic conditions alternate,resulting in alternation of brackish water and saline water and algae blooms with high salinity tolerance,high input of nutrients in lakes and adequate supply of provenances.Organic matter was best preserved and enriched to form thick oil shale deposits in strong reduction conditions during semi-deep and deep lakes period.