Research Of Sedimentary Facies Control Gas Of Chengzihe Formation In Muling Mining Area In Southern Jixi Basin

Jixi Basin is located in the east of Heilongjiang Province,covering Jixi City,Linkou County,Muling County,Jidong,and Mishan County with an area of 3780 km~2.Muling mining area is located in the south of Jixi Basin and is the peripheral region of Daqing exploration area.With the deepening exploration of Daqing Oilfield,the exploration has gradually expanded to more complex areas.Jixi and other peripheral basins have gradually attracted people's attention.Based on previous studies,sedimentology,well logging geology,and coal geology were applied to study the classification and distribution of sedimentary facies in Chengzihe Formation in Muling minning area in the southern Jixi Basin,and to divide the coalbed methane favorable zone in Muling mining area combined the distribution of dominant types of coal seam roofs.The Chengzihe Formation of southern Muling mining area in was mainly developed with terrestrial deposit,including underwater fans,fluvial,delta and lacustrine facies.The fluvial and delta facies were the most important sedimentary types during the early period of Chengzihe Formation,and the delta plain subfacies was the main coal forming environment in this period.In the middle period,the delta advanced eastward;the delta front enlarged;the lake bay swamp developed;the delta plain and the lake bay marsh subfacies were the main coal forming environments.In the late deposition period of the Chengzihe Formation,the scale of the delta began to shrink,while the lake basin expanded.The lake-bay swamp subfacies of the was the main coal-forming environment during this period.The main coal-forming period of the Chengzihe Formation in Muling mining area is early and middle stage.The coal thickness of the Chengzihe Formation in Muling mining area is relatively thin,about 6~10m.The main coal seam is No.14,with a thickness of2.67~4.0m and a burial depth of 791~853m.Coal seam ranks mainly include long-flame coal,gas coal and fat coal,followed by lean coal and poor coal.The degree of coal metamorphism in the region is slightly high,and is characterized by high in the west and low in the east,so it has good gas potential.The main tectonic styles in Muling mining area are graben-horst structure,monoclinic fault block,tilted fault block,and thrust-folded structure.The first three structures will cause the coal bed gas to escape through cracks.Therefore,the impact of tectonic action must be taken into account in evaluating the potential of coal bed methane.The coal seam of Chengzihe formation in Muling mining area is deep,and the content of coalbed gas increases with the increase of coal-bed depth.Therefore,the Chengzihe formation in Muling mining area has good conditions for the preservation of coalbed methane.Through analysis,three favorable zones for exploration and development of coalbed methane were identified:the south of Pinggang Coal Mine,the cooperation zone,and the eastern part of Dahengshan Coal Mine.