Study On The Characteristics Of Coalbed Methane Accumulation And Resource Prediction In Weizhou Mining Area,wuzhong City,Ningxia

The study area is located in the Weizhou mining area of Weizhou Town,Tongxin County,Wuzhong City,South Central Ningxia.The geotectonic location of the study area is located in the Ordos block of the North China block of the Qaidam North China plate.The stratigraphic division of the study area is the North China Qaidam stratigraphic region,the North China stratigraphic region and the table mountain Qinglong mountainous area.Based on the exploration results of 7 coalfields and the data of 4 coalbed methane parameter holes in Weizhou mining area,this paper studies the characteristics of coalbed methane accumulation in Weizhou mining area,delineates the areas where coalbed methane exists and benefits,forecasts the main coalbed methane resources,and has important guiding significance for further coalbed methane exploration and gas prevention in this area.Through the study of the data of the mining area,it is confirmed that the conditions of coalbed methane gas generation in the study area are good.The thickness of main coal seams 12,15 and 17 is about 2m,and the degree of metamorphism is relatively high.The maximum reflectivity(Romax)of main coal vitrinite is more than 2%,and the coal is fat coal,lean coal and anthracite.Coalbed methane is well preserved.After the formation of coal seam,in the process of structural evolution,with a period of time,the crust uplifted and suffered from weathering and denudation,but the overlying non coal measure strata were relatively thick.In addition,there were dense strata such as mudstone in the top and floor of coal seam and overlying strata,which was beneficial to the preservation of coalbed methane.Only the two wings of the syncline are seriously weathered and eroded,the coalbed methane is seriously dispersed,and the deep coalbed methane is well preserved;the lower limit of the gas weathering zone of the main coal seams(12,15,17 coal seams)in the study area is shallower than 400m in the vertical depth,and the buried depth of the deep coal seam of the syncline is more than 1400m,which is conducive to the generation and preservation of coalbed methane;the main structure of the mining area is a series of reverse faults associated with a syncline,forming a closed structure It is very beneficial to the preservation of coalbed methane and the accumulation of coalbed methane in local areas.In the closed syncline structure,the groundwater runoff is slow and the alternating circulation ability of deep groundwater is very weak,which has a favorable impact on the preservation of coalbed methane The storage conditions of coalbed methane in the study area are good.It is confirmed by four parameter wells of coalbed methane that the gas storage capacity of each coal seam in this area is strong,the gas content of main coal seam is 9.22m3/t-11.79m3/t on average,and the methane content of gas component is more than90%.The permeability and storage pressure of coalbed methane are generally low,the main coal seams are in high stress field,and the gas saturation is large.The results show that the areas below the aeolian oxidation zone are all favorable for coalbed methane accumulation,with an area of 255km~2.The predicted coalbed methane resources are 625×10~8m~3.