The Sedimentary Facies Analysis Of Jiufotang Formation In Naiman Depression Of Inner Mongolia

Naiman Depression is located in the Inner Mongolia Autonomous Region Tongliao City Naiman County territory,it is a secondary negative tectonic unit in the southwest side of Kailu Basin,its area is about 800 square kilometers.In this article,we take the Jiufotang Formation of Naiman Depression as a research object by using sedimentology,sequence stratigraphy,petrology,logging geology,petroleum geology and other theoretical knowledge,combining with the core drilling,logging data,seismic data and other data.we studied sedimentary facies and microfacies of Jiufotang Formation and analysed the sedimentary facies and the sedimentary microfacies,cleared the sedimentary system distribution,and combined with the regional tectonic basin to establish the sedimentary model of the basin evolution and forecast the interested zone.(1)The strata from the bottom boundary of Jiufotang Formation to the top boundary of Fuxin Formation are divided into a first grade sequence,and the sequence stratigraphic framework of the study area has been established.We think the lower Jiufotang Formation is Lowstad Systems Tract,and the upper Jiufotang Formation is Transgressive Systrems Tract.(2)Based on the observation of lithology and sedimentary structure of 12 coring wells in the study area,the rocks are divided into six categories,combined with the identification of the characteristics of logging curves,seismic feature identification and auxiliary analysis and tests,it is concluded that the Jiufotang Formation mainly developed the fan delta depositional system and we identified the three subfacies and five microfacies.(3)According to “points-lines-systems” thinking,we think the provenance is mainly from eastern and western of the study area.The large fan delta deposit develop and these sand bodies are contiguous distribution,mainly with the flower shape.In the lower Jiufotang Formation period,there is a small stock source in the northern depression,braided river delta and salt rock deposits.In the upper Jiufotang Formation,the small turbidite fan is developed in the central part of the lake basin.(4)According to the tentonic characteristics,lithologic charactese,dimentary iconographies and the statistics of the oil testing results,we conclude that the beneficial zone is Shuanghe Anticline,which is located in the central sag of Naiman Depression.