深盆气藏异常地层压力产生机制

运用典型深盆气成藏的活塞式原理讨论异常地层压力形式机制，认为：以气水活塞式排驱为特征的深盆气藏在其形成过程中表现为高异常压力；由于天然气的密度小于地层水密度，当天然气柱高度足够大时，深盆气藏内部将出现理论上的正常压力梯度的临界点，越过该点继续向下，深盆气藏压力梯度逐渐降低并出现低异常地层压力；从原始的生成状态到后期保存过程中的各阶段，深盆气藏的异常压力具有自变性特征。

Formation mechanism of abnormal pressures in deep-basin gas accumulation

Abnormal pressure is one of the important characteristics of deep basin gas or basin centered gas. By using the driving principles of piston movements, the paper discussed the pressure laws of typically deep basin gases. As a result, the abnormal pressures of deep basin gases that are of piston -fashioned driving between water and gas are supernormal ones forever. Since the density of gas is much lighter than that of formation water, theoretically critical point of normal pressure will be occurred within the accumulation of deep basin gas when the column of gas is long enough. Down-passing the critical point of normal pressure, the pressures of gas will gradually be subnormal ones. It is proved that the pressures of deep basin gases are of self-interacting from usually supernormal to subnormal during the diversification stages from accumulation to preservation of gases.