Study On Sequence Stratigraphy And Coal Accumulation Law Of Middle-Lower Jurassic Coal Measures In AKT Coal-bearing Basin,Southwest Of Tarim Basin

Based on previous research,this paper takes AKT coal-bearing basins as the main research object,and using the drilling cores,logging data collected in the field and coal-phase laboratory data to systematic study the Jurassic coal-bearing strata in the AKT coal-bearing basin.Multidisciplinary methods such as chemistry,coal petrology,and paleontology are used as theoretical guidance.In finally,a high-resolution sequence stratigraphic framework was established,and the further research were carried out on sedimentary facies,high-resolution sequence stratigraphy,coal accumulation law and its controlling factors.The main coal-bearing strata in the study area are the Lower Jurassic Kangsu Formation(J1K1-J1K2),and the Yangye Formation contains less coal.The study area is dominated by delta-shore shallow lake facies,and the analysis of single well and continuous well sedimentary facies has clarified the spatial combination rule of each sedimentary facies.It is found that the overall direction of the provenance in the study area comes from the south and the range of different periods is different.There have been changes and migrations,but there is a certain degree of inheritance as a whole.Based on the ?-level sequence divided by the predecessors,the coal-bearing strata of the Middle and Lower Kangsu Formation in the Jurassic system were finely divided into IV-level sequence and V-level sequence according to the logging curve characteristics.Among them,SQ2-1,SQ2-2 represents two grade ?sequence strata in the lower and upper sections of the Kangsu Formation,and SQ3-1,SQ3-2,and SQ3-3 represent three grade ? sequence strata in the middle and upper sections of the Yangye Formation.Through the chemical analysis of coal samples in the study area,it is found that the study area is a continental sedimentary environment from north to south,but it shows a trend of closer to the marine transition from south to south.The salinity of the sedimentary water medium is generally stable and less affected by seawater.hrough the analysis of coal seam thickness plane and coal seam cross-sectional profile,combined with formation thickness sandstone thickness contour map,it is found that the correlation between formation thickness and coal seam thickness is good,indicating a good match between settlement and supply.Based on the above,the coal accumulation law of the upper section of the Kangsu Formation shows a trend of rapid thinning from northeast to southwest.The coal mines that mainly exploit the coal seams of the Kangsu Formation are basically concentrated in areas of medium thickness.In the northwest of the North Line Goudong Coal Mine,the coal seam thickness decreases until the coal seam no longer develops.The development of the coal seam is related to structural subsidence,sedimentary system and system domain.The coal seam is mainly developed in the delta-shore shallow lake facies.The thickness of the coal seam in the low-level system domain is thin,and the lake intrusion system domain is favorable for coal development.