The characteristics and formation mechanism of coalbed methane reservoir pressure in Henan

Coalbed methane(CBM) reservoir pressure is one of the specific forms of the coal seam energy and the force for CBM migration and production.It affects not only the gas content and occurrence,but also the permeability of coal,thereby constraining CBM development.Based on well testing data of 9 CBM pilot wells,and combined with borehole pumping test data in the stage of coal exploration,the reservoir pressure characteristics in Henan have been systematically descripbed.The results indicated that CBM reservoir pressure varied in a wide range,from under pressure to over pressure.The reservoir pressure is caused by recharge,migration,and stagnation of groundwater.The under pressure is commonly formed in the runoff zone,and the normal pressure and over pressure in the weak runoff zone and the deep stagnant zone.CBM migration with groundwater has not only been proved by hydrodynamics,but also verified from the gas composition and genesis.The formation mechanism of this kind of reservoir pressure is similar to commercial development CBM reservoir under commercial development at home and abroad.The abnormal high pressure area is CBM-enriched and favorable development area.