Geological Structure Characteristics of No.1 Well in Dahuangshan and Its Influence on Coal Seam Gas Storage
In order to anlysis the influence of geological structure and its evolution on the gas occurrence in the coal seam of Dahuangshan No.1 Well in Xinjiang,this paper study the geological structure and evolution characteristics of the mine field,burial uplift history of coal bearing strata,metamorphism of coal seams,and gas generation and occurrence characteristics,so as to provide theoretical guidance for the prevention and control of gas disasters in Dahuangshan No.1 Well.The research shows that the mine field is located in the piedmont arcuate thrust fold belt of the thrust nappe structural belt on the northern edge of Bogeda mountain,controlled by high angle imbricate thrust fault and north-south structural compression stress,and the main structure of the mine field is shown as an arc-shaped closed reverse steering slope with southward dipping axial plane cut by NE and NW conjugate strike slip translational faults on the north and south wings.The coal bearing strata in the mine field have undergone two main stages since sedimentation.The first stage is the rapid subsidence and the maximum burial depth of about 4 000m in the Late Jurassic.The deep thermal metamorphism caused the coal seams to reach the gas coal metamorphic stage and the peak of thermal gas and gas appeared;The second stage is the continuous compression and uplift deformation of the coal bearing strata,resulting in a large amount of coal seam gas escape.Controlled by the active folding effect of tangential strain,the compression stress on the coal seams in the north and south wings of the mine field syncline towards the core is increasing,resulting in smaller porosity and permeability coefficients of the coal seams,and higher gas content and pressure in the coal seams.Controlled by the background of the east-west differential compression arc structure,the gas content and pressure in the western coal seam of the northern wing are generally higher than those in the eastern part,and show a gradually decreasing trend from west to east.Controlled by strike slip and displacement faults,local high values of gas content and pressure in coal seams near the faults occur.
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