An Analysis of the Roles of Stress, Temperature, and pH in Chemical Compaction of Sandstones
An Analysis of the Roles of Stress, Temperature, and pH in Chemical Compaction of Sandstones
复制标题
应力、温度和 pH 在砂岩化学压实作用中的作用分析
DOI：
10.1306/070802730064
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发表时间：
2003
影响因子：
2
通讯作者：
M. Cheadle
中科院分区：
文献类型：
--
作者：
H. Sheldon;J. Wheeler;R. Worden;M. Cheadle
摘要 化学压实，也称为压力溶解，涉及沿颗粒接触的溶解以及溶质通过扩散输送到相邻孔隙空间。扩散的驱动力是化学势梯度，因此化学压实需要沿颗粒接触的化学势梯度持续存在，以连续驱动扩散。由于颗粒表面应力的不均匀分布，多孔岩石中存在这种梯度。化学压实的速率取决于应力、流体压力、温度和孔隙流体的成分，而孔隙流体本身又取决于添加或去除溶质的各种过程。另一种化学压实模型利用片状硅酸盐对 pH 值的影响来解释与缝合线相邻的颗粒的局部溶解，或者片状硅酸盐沿着颗粒接触面存在的情况。在此模型中，化学压实速率与应力和流体压力无关，仅取决于温度。该模型是站不住脚的，因为所提出的机制无法产生驱动扩散所需的持续化学势梯度。然而，片状硅酸盐可能会增加化学压实的速率，因为它们对溶解和扩散速率有影响。化学压实导致的各向异性组构的发展，以及碳酸盐岩和砂岩中广泛存在的缝合线，与pH模型不一致，为化学压实中应力的作用提供了有力的支持。
ABSTRACT Chemical compaction, also known as pressure solution, involves dissolution along grain contacts and transport of solute to the adjacent pore space by diffusion. The driving force for diffusion is a gradient in chemical potential, therefore chemical compaction requires persistent gradients in chemical potential along grain contacts, in order to drive diffusion continuously. Such gradients exist in porous rocks because of the heterogeneous distribution of stress over the grain surfaces. The rate of chemical compaction depends on stress, fluid pressure, temperature, and the composition of the pore fluid, which itself depends on various processes that add or remove solute. An alternative model of chemical compaction invokes the effect of sheet silicates on pH to account for localized dissolution of grains adjacent to stylolites, or where sheet silicates are present along grain contacts. In this model, the rate of chemical compaction is independent of stress and fluid pressure, depending only on temperature. This model is untenable because the proposed mechanism cannot give rise to the persistent gradient in chemical potential required to drive diffusion. However, sheet silicates may increase the rate of chemical compaction because of their influence on dissolution and diffusion rates. The development of anisotropic fabrics as a result of chemical compaction, and the widespread occurrence of stylolites in carbonates as well as sandstones, are inconsistent with the pH model and provide strong support for the role of stress in chemical compaction.