Research On Sedimentary Facies And Coalbed Methane Exploration Potential Of Chengzihe Formation In Jixi Basin

The Jixi basin is mainly developed delta facies and lacustrine facies,and the river facies developed in some areas of the northern part of the basin.In the early stage of the deposition of the Chengzihe Formation,the northern delta and the southern delta of the basin are integrated as one whole.The eastern part of the basin is the shallow lake,the deep lake and the semi-deep lake subfacies.In the middle stage of the Chengzihe Formation the northern delta and the southern delta is separated,and the middle of the basin is developed lacustrine facies.In the eastern part of the basin,a large-scale lake and marsh swells are developed in the eastern part of the basin,and alluvial plains are developed in the northwest and southeastern fronts of the basin.The scale of the two northern and northern deltas is further expanded in the late Chengzihe Formation,and the scale of the alluvial plain is expanded,Thus the lake in the middle of the basin scale reduced.The favorable coal-forming environment in the Chengxihe Formation of the Jixi Basin is favorable for the sub-phase of the two delta plains in the north and south and the lagoon marsh subfacies developed in part.The types of lithologic assemblages of the main coal seam roofs in the Chengzihe Formation of the Jixi Basin can be divided into three types: the shale-type dominated roof,the hard rock type dominated roof and the broken roof,and the shale-type roof is the rich Set and save the most favorable.The sedimentary facies of the sediments in most areas of the basin are formed in the upper part of the basin,and the dominated top plate of the hard rock is developed only in the area of the basin.It can be seen that the exploration potential of coalbed methane in Jixi basin is large.The main coal seam in Chengzihe Formation of Jixi Basin is mainly composed of vitrinite and low content of chitin group,which is a high ash and low sulfur coal.The main types of coal slabs are dominated by bright coal,followed by semi-bright coal and semi-dark coal.The main coal seam coal to coal,coking coal,followed by long flame coal,and a small amount of fat and lean coal.Jixi basin coal seam coal metamorphism is high,with good gas potential,favorable area of coalbed methane development.The geological structure of The Jidong depression in the north of the Jixi basin and the Muling Depression in the south of the Jixi basin are dominated by the large-scale reclining of the extrusion,which is favorable for the enrichment and preservation of the coalbed methane.The coalbed gas content in the basin has the rule as the burial depth of the coal seam increases,and the coal seam in the north belt of the basin is larger than that of the south coal seam.In the southern part of the basin and the northern part of the basin is relatively simple hydrological conditions,through the water block and water control gas control is basically conducive to the preservation of coalbed methane.The watershed near the Dunmi fault zone near the fault development,aquifer rich water and good contact with the coal seam hydraulic,groundwater in the process of carrying the coal in the movement of gas migration and escape.According to various geological conditions,two coalbed methane zones in Jixi Basin are divided into: Langling-Donghai coalbed methane favorable area and Hezuo coalbed methane favorable area.