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超压可由下列作用所产生:①压应力增加,②孔隙流体或岩石基质体积变化,③流体流动或浮力。埋藏过程中的负载由于不平衡压实作用(尤其在低渗透性沉积物的快速沉降过程中)可以产生严重的超压现象。水平应力的变化在构造活动区可以迅速地产生和耗散大量的超压。涉及体积变化的超压机制必须具有良好的封闭条件才能成为有效。与水热膨胀和粘土脱水作用有关的流体增加太小,不足以产生显著的超压现象,除非存在极佳的封闭条件。生烃作用和油裂解成气可能产生超压现象,这取决于干酪根类型、有机质丰度、温度史以及岩石的渗透率。但是,这些作用过程在一个封闭体系中可能受自我限制,因为压力的增加可能会进一步抑制有机质变质作用。生烃作用和热裂解产生超压的潜力目前尚未得到证实。在埋藏较浅并“具有良好水管系统”的盆地中,由于水头而产生的流体流动可以产生严重的超压现象。计算结果表明,油气浮力和渗透作用只能产生少量的局部超压现象。不可压缩流体中的气体向上运动也可以产生显著的超压现象,但对此需做进一步的研究。在许多沉积盆地中,最可能产生超压的机制往往与应力有关。
Overpressure can be caused by the following effects: (1) increased compressive stress, (2) changes in pore fluid or rock matrix volume, (3) fluid flow or buoyancy. Buried loads can cause severe overpressurization due to unbalanced compaction, especially during rapid settling of low permeability sediments. Changes in horizontal stress in the tectonic activity zone can quickly generate and dissipate a large amount of overpressure. Overpressure mechanisms involving volume changes must have good containment conditions to be effective. The increase in fluid associated with hydrothermal expansion and clay dehydration is too small to produce significant overpressure unless there is excellent containment. Hydrocarbon generation and oil cracking into the gas may produce overpressure, depending on the type of kerogen, abundance of organic matter, temperature history, and permeability of the rock. However, these processes may be self-limiting in a closed system because the increased pressure may further inhibit the metamorphism of the organic matter. The potential for overpressure due to hydrocarbon generation and pyrolysis has not yet been demonstrated. In basins that are shallow buried and have a “good plumbing”, fluid flow due to the head can create severe overpressurization. The calculation results show that the buoyancy and infiltration of oil and gas can only produce a small amount of local overpressure. Upward movement of gas in an incompressible fluid can also cause significant overpressure, but further research is required. In many sedimentary basins, the mechanism most likely to generate overpressure is often stress related.