Controlling factors of coalbed methane and accumulation areas in Galilee basin in Australia

Galilee basin is the main coal basin in eastern Australia and also the important area of coalbed methane exploration and development. Through the coal quality, gas source, structure evolution, sealing conditions and hydrology conditions, main gas control factors and accumulation areas were studied. The researches show that coal quality and the ability of generating gas are not variable, coal began generating gas continuously from Mid-Creta-ceous; the tectonic movement in Late Cretaceous destroyed the gas accumulation; mudstone is more developed in the area between the fluvial fans, forming good cap; water retention area was formed near the center of the basin, the salinity is higher and the formation water is mainly of calcium chloride type, which are benefit for the gas preservation; the nitrogen proportion of the desorbed gas and gas content also show that the gas-bearing property is better. Development of good local cap and water retention environment are the main gas controlling factors of coalbed methane accumulation. The gas accumulation conditions are better in the northeast of Hulton-Road structure, the east of Marathon monoclinic and the north of Berly uplift in the central basin are the coalbed methane accumulation areas.