准噶尔盆地南缘煤储层多尺度孔缝结构差异及影响因素OA

Coalbed methane resources are abundant in the southern margin of the Junggar Basin(hereafter referred to as the southern Junggar Area),and are mainly hosted in the Jurassic Badaowan Formation and Xishanyao Formation.To clarify the differences in pore-fracture development characteristics and their influencing factors for coal reservoirs in the Badaowan Formation of the Fukang mining area and in the Xishanyao Formation of the Qigu fault-fold belt in the southern Junggar area,CT scanning,scanning electron microscopy(SEM),high-pressure mercury intrusion,low-temperature nitrogen adsorption and carbon dioxide adsorption ex-periments were conducted,and a full-aperture stitching technique was applied for analysis.The results show that the coals in the study area are all bituminous coals with similar reflectance and medium coal rank.The coal quality of the Fukang mining area(vitrinite content of 81%-88%)is slightly better than that of the Qigu fault-fold belt(vitrinite content of 70%-78%),while the coalification degree in the Qigu area is slightly higher.In the Fukang mining area,the coal reservoirs have few developed fractures;pores are dominated by tissue pores,with a small number of gas pores locally developed.The theoretical adsorption capacity is stronger with an average Langmuir volume of 18.75 cm3/g and an average specific surface area of 74.13 m2/g;however,affected by coal quality,the infilling effect of ash re-duces the total pore volume pores are dominated by gas pores with higher proportions of mesopores and macropores.In the Qigu fault-fold belt,the average Lang-muir volume is 10.83 cm3/g and the average specific surface area is 68.05 m2/g.Intensive tectonism provides conditions for fracture development;cleats and frac-tures are well developed overall,resulting in the advantageous reservoir physical properties of high porosity and permeability and low damage.Comprehensive analy-sis indicates that the Fukang mining area has better adsorption and high gas content,but fractures are not well developed,free gas is difficult to accumulate,and gas desorption is difficult;the Qigu Area has longer-term and more stable development potential.These results provide a theoretical basis for efficient exploration and development of coalbed methane in the study area.