Stylolites in limestones: Barriers to fluid flow?

Abstract

International audienceStylolites--products of intergranular pressure-solution--are laterally extensive, planar features. They are a common strain localization feature in sedimentary rocks. Their potential impact on regional fluid flow has interested geoscientists for almost a century. Prevalent views are that they act as permeability barriers, although laboratory studies are extremely rare. Here we report on a systematic laboratory study of the influence of stylolites on permeability in limestone. Our data demonstrate that, contrary to conventional wisdom, the studied stylolites do not act as barriers to fluid flow. In detail, when a stylolite occurs perpendicular to the direction of flow, the permeability simply follows the same power law permeability-porosity trend as the stylolite-free material. We show, using a combination of high-resolution (4 µm) X-ray computed tomography, optical microscopy, and chemical analyses, that the stylolites of this study are not only perforated layers constructed from numerous discontinuous pressure solution seams, but comprise minerals of similar or lower density to the host rock. The stylolites are not continuous high-density layers. Our data affirm that stylolites may not impact regional fluid flow as much as previously anticipated

A new stylolite classification scheme to estimate compaction and local permeability variations

“…The most important ingredient is the 535 collection of sealing material in the stylolite. If the material is not sealing (as was 536 the case in the study of Heap et al, 2014) the stylolites or part of them cannot be 537 local barriers to fluid flow. In general stylolites can perform three different 538 structural changes to produce barriers: (i) they can collect impermeable material 539 and thus build up a barrier, (ii) they can intensify the existing sealing properties 540 of layers and (iii) they can offset existing barriers ( fig.…”

“…If we perform 564 a two--dimensional analysis of the stylolites shown in figure 1a and b, stylolite 1b 565 has a sealing capability of only 15%, whereas stylolite 1a has a local sealing 566 capability of around 75%. Further research is needed in this direction in order 567 to quantify sealing qualities and local versus larger--scale permeabilities of these 568 complex structures following the work of Heap et al (2014 by the dissolution rate of each particle (1 represents 0 pinning strength). For the 856 matrix 10% of particles dissolve a factor x times the dissolution--rate of the 857 matrix.…”

“…This weakness of the stylolite plane and its tendency to fracture may be 91 enough to enhance fluid flow along the stylolite plane. In addition, accumulation 92 of materials, such as clays, on the stylolite plane may reduce the permeability 93 perpendicular to the stylolite plane (Dunnington, 1967;Nelson, 1981 Other studies found no effect of stylolites on a rock's overall permeability (Lind 99 et al, 1994; Heap et al, 2014 We use the software "ELLE -Latte" ( springs are used to calculate the local stress field at a particle and its elastic 239 energy !" from the strain tensor !"…”

Sinkholes and the Engineering and Environmental Impacts of Karst: Proceedings of the Fourteenth Multidisciplinary Conference

“…There are many stylolites found within the limestone beds as well, along the planes of which additional points of weakness exist. These lateral stylolitic seams can enhance fluid flow and dissolution along their path, where delamination and cracking can occur (Heap et al 2013), as was observed in the cave. Over time, a breakout dome formed and migrated upward, thinning the bedrock support and creating a situation wherein structural failure and the sinkhole collapse was imminent.…”

Reconstruction of the pre-compactional thickness of the Zechstein Main Dolomite in northwest Poland

“…First, it records the intensity of compaction and reflects the expulsion of reservoir fluids during primary migration and, second, it controls the transformation of reservoir from porous to dual, porous-fractured. The systems of tectonic fractures together with the systems of stylolite seams both influnce the migration of reservoir fluids (Stockdale, 1926;Ramsden, 1952;Radlicz, 1966;Dunnington, 1967;Semyrka, 1985;Strzetelski, 1977;Koepnick, 1988;Aydin, 2000;Agosta et al, 2009;Agosta et al, 2010;Heap et al, 2014).…”