The inherent heterogeneity of carbonate rocks suggests that carbonate-hosted fault zones are also likely to be heterogeneous. Coupled with a lack of host–fault petrophysical relationships, this makes the hydraulic behaviour of carbonate-hosted fault zones difficult to predict. Here we investigate the link between host rock and fault rock porosity, permeability and texture, by presenting data from series of host rock, damage zone and fault rock samples from normally faulted, shallowly buried limestones from Malta. Core plug X-ray tomography indicates that texturally heterogeneous host rocks lead to greater variability in the porosity and permeability of fault rocks. Fault rocks derived from moderate- to high-porosity (>20%) formations experience permeability reductions of up to six orders of magnitude relative to the host; >30% of these fault rocks could act as baffles or barriers to fluid flow over production timescales. Fault rocks derived from lower-porosity (<20%) algal packstones have permeabilities that are lower than their hosts by up to three orders of magnitude, which is unlikely to impact fluid flow on production timescales. The variability of fault rock permeability is controlled by a number of factors, including the initial host rock texture and porosity, the magnitude of strain localization, and the extent of post-deformation diagenetic alteration. Fault displacement has no obvious control over fault rock permeability. The results enable better predictions of fault rock permeability in similar lithotypes and tectonic regimes. This may enable predictions of across-fault fluid flow potential when combined with data on fault zone architecture.

中文翻译：

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碳酸盐断层岩渗透率：以马耳他为例

碳酸盐岩固有的非均质性表明碳酸盐岩断层带也可能是非均质的。再加上缺乏宿主-断层岩石物理关系，这使得碳酸盐岩宿主断层带的水力行为难以预测。在这里，我们通过提供来自马耳他正常断层、浅埋石灰岩的一系列主岩、损伤带和断层岩样本的数据，研究了主岩和断层岩孔隙度、渗透率和质地之间的联系。岩心塞 X 射线断层扫描表明，质地非均质的主岩导致断层岩孔隙度和渗透率的更大变化。来自中高孔隙度（>20%）地层的断层岩的渗透率相对于母体减少了多达六个数量级；> 这些断层岩中有 30% 可以在生产时间尺度上充当流体流动的挡板或障碍。源自低孔隙度 (<20%) 藻类灰岩的断层岩的渗透率比其宿主低多达三个数量级，这不太可能影响生产时间尺度上的流体流动。断层岩渗透率的可变性受多种因素控制，包括初始围岩结构和孔隙度、应变局部化的大小以及变形后成岩蚀变的程度。断层位移对断层岩渗透率没有明显的控制。结果能够更好地预测相似岩型和构造体制下的断层岩渗透率。当与断层带结构的数据相结合时，这可以实现跨断层流体流动潜力的预测。