Water-rock interactions, fractured rocks

Lipfert, G., and Reeve, A (2004). Fracture-related geochemical controls on As concentrations in ground-water. In Proceedings of the 11th International Symposium on Water Rock Interaction (R. Wanty and R. Seal, eds.), Vol. 2. pp. 431-434. Balkema, New York. 

Marshall D. D., Whelan J. F., Peterman Z. E., Futa K., Mahan S. A., and Struckless J. S. (1992) Isotopic studies of fracture coatings at Yucca Mountain, Nevada, USA. In Proceedings 7th Water—Rock Interaction Symposium Park City, UT (eds. Y. K. Kharaka and A. S. Maest). A. A. Balkema, Roterdam, pp. 737—740. 

TuUborgE. L. (1989) S Oand S C in fracture calcite used for interpretation of recent meteoric water circulation. In Proc. 6th Int. Symp. Water-Rock Interaction (ed. D. L. Miles). Malvern, UK Balkema, Rotterdam, The Netherlands, pp. 695-698. 

Characterizing the chemical containment properties of the deep geosphere water-rock interactions in relation to fracture systems within deep crystalline rock in the Tono area, Japan... 

Water-rock interactions in the fractures and fracture zones... 

Lu Zude. 2010. Experimental and theoretical analysis on mechanical properties of fractured rock under water-rock interaction[D]. Wuhan Chinese Academy of Science, (in Chinese). 

In shales, mud weight is usually sufficient to balance formation stress, as these wells are usually stable. With water based mud, chemical differences can cause interactions between mud and shale that lead to softening of the native rock. Highly fractured, dry, brittle shales can be extremely unstable (leading to mechanical problems). 

A third explanation is that the different rates could reflect differences in the pH of the waters. The rate of feldspar dissolution is enhanced at pH > 7 (e.g. Knauss Wolery 1986). This fact might explain the observation that the alteration is more intense at DH-3/26 m where the sampled water had a pH of 8.9-9.3, than at DH-4/80 m where the water had a pH of 6.8. Knauss Wolery (1986) found a rate of albite dissolution some five times faster at the higher pH levels. However, it follows from this hypothesis that waters in different fractures have acquired distinct pH values. Once again, this observation may reflect the differing natures of water/rock interactions in different fractures, which may in turn be linked to variable hydraulic properties of different fractures. 

In porous or fractured water-bearing rock, the electrolytic conductivity of the water and interactions between solid and fluid components create an enhanced electrical conductivity. 

In oceanic fracture zones as well as in actively-upwelling forearc mud volcanoes, seawater or other marine fluids interact directly with mantle rock (Bonatti 1976 Fryer 1985). Serpentinization of mantle rocks at temperatures broadly <350°C involves influx of water, as well as general increase in Li concentration in the newly-formed hydrous assemblage. Considering the low temperatures involved, Li isotope exchange during seawater-mantle... 

In terms of Li content and isotopic signature, the Yellowknife mine waters are similar to waters from Sudbury (Ontario) area mines (0.05 to 2.9 ppm Li and 5T i = +27.9 to +42.6 Bottomley et al. 2003). Composihons of the Sudbury brines are consistent with predominance of preserved marine Li. These waters contrast with samples from mines in central Manitoba, which are dilute (Li concentration < seawater) and show a wide range of 5 Li (+15.0 to +46.9 Bottomley et al. 2003). These waters are plausibly mixtures of isotopically heavy brine (developed through fluid-rock interachon in fracture zones) and waters that had interacted with isotopically hght cormtry rocks. 

The rate of flow between fluids in fractures and in the rock matrix is a crucial factor for transport and reaction in fractures. For consistency with the formulation for flow between fractures and matrix used in the Yucca Mountain Project, the reactive surface area for minerals in unsaturated fractures has been related to the fracture-matrix interaction area based on a modified form of the Active Fracture Model (Liu et al., 1998 Sonnenthal el al., 2003). In this way, the wetted surface area for mineral-water reactions is consistent with that for flow and diffusion. 

We envisage that the fluid flow takes place in a 3-dimensional network of fractures (or channels) with a stochastic distribution of conductances (Moreno and Neretnieks 1993). In each channel the stream of water will be in contact with the rock surfaces. Intuitively it is conceived that the larger the contact surface there is for a given stream of water the stronger will be the interaction between flowing water and rock. This is the key issue in the paper. Several models have been proposed that account for the matrix diffusion effects. In all, the ratio of FWS to flowrate q enters as a key entity. In this paper we use a 3-dimensional fracture network model that is simplified by letting each fracture... 

On the other hand, overlooking interactions may have severe consequences in modelling utility. For example, in hydropower tunnels hydraulic fracturing may be an issue (if the water pressures are high in relation to the rock stress), but the failure consequence would be overlooked unless this process were to be included in the description of the mechanical system (Stille et al., 2003). 

The efficiency of a rock formation as a transport barrier depends on fluid flow and on radionuclide retention in the rock due to a variety of physical and chemical processes. Open fissures or fractures in the rock provide pathways through which water and radionuclides may travel. Although most radionuclides have a strong tendency to sorb to mineral grains in the rock, tracers first have to diffuse from fractures into the rock matrix in order to access the extensive pool of sorption sites (Neretnieks, 1980). Diffusion in turn depends on mass transfer properties of the rock matrix and on the hydrodynamics of fracture networks, emphasizing the interaction between water flow, advective transport and retention processes. Although models for reactive transport in discrete fracture networks have been around for some time, it is only recently that a theoretical framework is available for systematic studies of the hydrodynamic impact on retention (e.g., Cvetkovic et al., 1999, 2002). 

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