关键词: 深盆气藏, 压力特性, 成因机理, 异常地层压力

Abstract: Deep basin gas is an abnormal gas accumulation with characters of subnormal pressure and gas-water inversion caused essentially by its tight reservoir. Under formation of deep basin gas pool,the formation pressure at any point in the gas reservoir is equal to the sum of hydrostatic pressure above the gas-water interface and the pressure of gas column from the point to the gas-water interface.Since the density of gas is far lower than that of water,the sum pressure mentioned above is smaller than that of two parts being both water,and the deep basin gas pool behaves the underpressure feature.The connectivity,height of gas pillar and distribution range of gas-bearing formation can be determined according to the feature and scale of subnormal pressure.However,under formation of common gas pool,the formation pressure at any point in the gas reservoir is equal to the difference between the hydrostatic pressure above the gas-water interface and the gas column pressure from the point to the gas-water interface.Since the density of gas is lower than that of water,the sum pressure mentioned above is bigger than that of the hydrostatic pressure above the point,and the common gas pool behaves the superpressure feature.Under general geologic conditions, supernormal pressure is of the general feature of common gas pool,and it couldn't be employed as a distinct symbol of deep basin gas pool,except in several special cases.

Key words: deep basin gas pool, pressure features, pressure formation mechanism, subnormal formation pressure