[科学探索]地层压力下降会导致骨架颗粒膨胀吗？ [复制链接]

Reservoir Characteristics
Oil is present in three members of the Cambrian
Sandstone Formation but the principal reservoir is
the R-a Zone (“Zone anisométrique”). All members
are more or less fractured, which locally improves
the producibility of the reservoir, but the matrix
porosity and permeability are still of prime
importance for the long-term performance of the
field (Massa et al., 1972). However, the presence of
significant faults means that the reservoir is
subdivided into separate compartments, within
which minor permeability barriers may be present
due to mineralised fractures, microbreccias and
stylolites.
能够改善产能，不能说裂缝没有一定的开启度。

Type of fracture - Massa et al. (1972) have studied
the fractures in the Cambrian sandstone, both at
outcrop in the Tassili N Ajjer Hills (northern Hoggar
Range) to the south of Hassi Messaoud, and also in
over 100 cored wells in the field itself. They have
described a series of macrofractures (visible in
hand specimen or core) and microfractures (visible
mainly in thin-section) in the sandstone.
Macrofractures are either vertical to sub-vertical
(Fig. 13A), or inclined at 75o, and generally occur as
an orthogonal set, with macrofractures in one
direction being much more abundant than the other.
The principal set of macrofractures are most
abundant in the upper part of the Cambrian
sandstones where the density of the fractures is
generally 6 to 20 per metre in the top 15 m, although
it can exceptionally be as high as 50 to 100
fractures/metre. The macrofractures become less
common with depth, where generally there are only
0.3 to 0.6 fracture/metre. The orthogonal set of
macrofractures are less abundant and have
frequencies which vary from 10 per metre at the top
of the reservoir, to 0.5 per metre at depth. Massa et
al. (1972) also noted a reduction in fault density with
a reduction in hardness of the sandstones
essentially caused by a reduction in the amount of
siliceous cement.
低渗透油藏断层附近有时在钻井过程中存在微弱泥浆漏失现象。

Microfractures seen in thin-section can vary in
aperture from several tens of microns to several
millimetres and can be either open, partly
mineralised or completely mineralised (Fig. 13B, C
and D). The commonest minerals in the
microfractures are anhydrite, barite, siderite, dickite,
other clay minerals, quartz and pyrite (Massa et al.,
1972). It can be shown that dickite crystallised first
in the microfractures, while anhydrite is a late-stage
mineral.
局部充填的裂缝在低渗油藏中非常重要。

Origin of fracture porosity - The macrofractures
described by Massa et al. (1972) are believed to
have originated at the same time as the faults
affecting the field, that is, principally during the
Hercynian orogeny. Both the faults and many of the
macrofractures have a strong strike-slip component
and have originated in a compressive regime (Fig.
14).
地下的裂缝是有一定的孔隙度的，只是很小，但对渗透率的贡献很大，裂缝不开启恐怕无法形成裂缝孔隙度。

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这篇文献的31页对有部分矿物充填的裂缝有较好的描述。

A novel technique for modeling
fracture intensity: A case study
from the Pinedale anticline
in Wyoming
上面是一篇文献名，可以解释为什么裂缝在地下可以张开，局部的变形给其张开提供了空间，而裂缝两侧的岩石（fracture wall）提供了来自上方压力的支撑。

传统教材是不是把内压和地层压力混淆了，或者说他们认为地层压力是外压

真理不容易啊。

无论地层压力下降还是升高，岩石骨架颗粒几乎不会膨胀，也几乎不会压缩。在地层压力变化时，岩石骨架颗粒的体积不变的假定。完全能够满足你们油藏工程的要求。因为那点体积变化对你们的原油产量影响太小了。众所周知，水都可以假定是不可压缩的，为什么固体的岩石骨架那么一点点微小压缩或膨胀还要考虑呢？？？？？？这不是笑话吗？岩石骨架体积几乎是不变的，但是不等于在地层压力作用下岩石骨架不变形，这是两个不同的物理概念。在地层压力降低很大时，虽然岩石骨架体积几乎不变，但是由于岩石孔隙度减小，宏观表现为地层会沉降，渗透率会下降。反之亦然，在地层压力升高很多时，虽然岩石骨架体积几乎不变，但是由于岩石孔隙度增加甚至是裂缝增加，宏观表现为地层会上升，渗透率会升高。根据岩石骨架体积不变的假设，我已经推到出了岩石初始孔隙度（无载荷）和任意载荷下孔隙度与岩石表观体积应变之间的关系。经过实验验证是正确的。有兴趣者可以与我联系。

wks9998:无论地层压力下降还是升高，岩石骨架颗粒几乎不会膨胀，也几乎不会压缩。在地层压力变化时，岩石骨架颗粒的体积不变的假定。完全能够满足你们油藏工程的要求。因为那点体积变化对你们的原油产量影响太小了。众所周知，水都可以假定是不可压缩的，为什么固体的岩石骨架那么一点点微 .. (2016-03-28 09:30) 

阿亮教授，岩石骨架体积不变，怎么能够说岩石就是刚体呢？我们假设橡胶体积不变，不等于它不发生变形呀？？？？？岩石骨架体积不变与岩石骨架不变形（刚体）是两个概念。