Jurassic coal bed methane characteristics and gas-bearing property evaluation in Iqe Coalfield, northern Qaidam Basin

The northern margin of the Qaidam Basin is rich in coal and coal bed methane resources. The Iqe Coalfield is a typical area rich in coalbed methane, which mainly occurs in the Shimengou and Dameigou formations in the Middle Jurassic. Gas contents vary in different areas of the Iqe Sag influenced by regional tectonics. The M5 coal seam of the Shimengou Formation and the M7 coal seam of the Dameigou Formation show a good resource prospect. The relationship between depth and gas-bearing properties shows a gas-bearing gradient and the discreteness of the relationship between depth and gas-bearing property is small in the Erjingtian area. The gas-bearing capacity of M7 coal seam decreases first and then increases with burial depth, and increases first and then decreases in the Caxiu, Yangshuihe and Yuka areas. The gas-bearing properties of M7 coal seam of Jurassic in the Iqe Sag vary greatly in different tectonic units and show obvious heterogeneity. On the whole, the gas-bearing capacity of coal seams in the western Iqe Sag is significantly higher than that of the eastern part, and slightly better in the north than in the south, which shows a trend of decreasing first and then increasing from south to north. There are two relatively high gas content areas in a small anticline structure in the north of the Iqe Coalfield, controlled by F2 and F10 faults, and the coal seam gas content gradually increases from south to north. While the gas content is generally lower in the Beishan and Erjingtian areas in the east of the Iqe Coalfield.