Fluid flow water/rock interactions

Hydrothermal alteration is reflected by the changes in many variables (temperature, water/rock ratio, extent of water-rock interaction (reaction progress), reaction rate, flow rate of fluids etc.) (Fujimoto, 1987). Theoretical and experimental works on hydrothermal alteration were reviewed by Meyer and Hemley (1967), and Rose and Burt (1979). 

Fig. 2.11. Configurations of reactive transport models of water-rock interaction in a system open to groundwater flow (a) linear domain in one dimension, (b) radial domain in one dimension, and (c) linear domain in two dimensions. Domains are divided into nodal blocks, within each of which the model solves for the distribution of chemical mass as it changes over time, in response to transport by the flowing groundwater. In each case, unreacted fluid enters the domain and reacted fluid leaves it.

Marked differences in whole-rock 5 0 values are acquired during water/rock interaction due to variation in temperature (Fig. 1). Contour maps of whole-rock 5 0 record cumulative paleo-heat and fluid flow. 

The long time scales (104 to 10s m.y.) involved in deformation and synkinematic isotope exchange in white mica provide a robust, long-term average of meteoric water-rock interaction, characteristic for the time scales of major readjustments in surface elevation. Thus the hydrogen isotope record in recrystallized muscovite provides a direct link between the tectonic and fluid flow history in the shear zone and temporal variations in meteoric water composition due to changing surface elevation. 

Oil or water chemistry can be determined from fluid samples or from core extracts. Oil or gas variations may be inherited from the filling history, or be modified by in-reservoir processes such as described above for density. Water variations relate to either water-rock interaction (e.g. dissolution of salt or feldspars), or to regional flow patterns (e.g. influx of meteoric water). 

In this book we considered mass transfer and elemental migration between the atmosphere, hydrosphere, soils, rocks, biosphere and humans in earth s surface environment on the basis of earth system sciences. In Chaps. 2, 3, and 4, fundamental theories (thermodynamics, kinetics, coupling model such as dissolution kinetics-fluid flow modeling, etc.) of mass transfer mechanisms (dissolution, precipitation, diffusion, fluid flow) in water-rock interaction of elements in chemical weathering, formation of hydrothermal ore deposits, hydrothermal alteration, formation of ground water quality, seawater chemistry. However, more complicated geochemical models (multi-components, multi-phases coupled reaction-fluid flow-diffusion model) and phenomenon (autocatalysis, chemical oscillation, etc.) are not considered. 

A modelling approach that could fulfil this need is based on the stationary-state approximation to coupled fluid flow and water-rock interaction (Lichtner 1985, 1988). This model represents the chemical evolution of an open, flow-through system as a sequence of relatively long-lived stationary states of the system, which are linked in time by short-lived transients. The basis for the model is the observation that within a representative elemental volume of a rock-water system, the aqueous concentration of any particular species is generally much less than its concentration in minerals. Long periods of time are therefore necessary to dissolve, or precipitate, minerals such that the spatial distribution of mineral abundances, surface area, porosity and permeability is altered significantly. Each time interval represents a stationary state of the system, in which fluid composition, reaction rates and the distribution of primary and alteration minerals vary only as a function of position in the flow path, not of time. 

Bj0rlykke K. and Lynch F.L. (1997) Mineral/water interaction, fluid flow, and Frio sandstone diagenesis evidence from the rocks—Discussion and Reply. Am. Assoc. Petrol. Geologists Bull. 81, 1534-1537. 

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... 

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). 

Abstract Accidents of some arch dams show that dam failures are mainly caused by crack or failure of their foundation rocks, which are directly related to water seepage in the rock. This kind of fluid-rock interaction has an important influence on deformation and stress characters of the dam-rock system. In this paper, the stress and flow fields of dams and their foundation rocks are studied as a coupled system, using visco-elastic constitutive models and finite element solution method. The developed models and FEM technique were applied for analysing the continuous displacement of the 13 dam section of the Longyangxia Dam, and the calculated results agree well with the measured ones. 

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. 

It may be necessary to iterate through the sequence of these steps a number of times before a model can be considered to be validated. The aim of the modelling described in this paper is to predict the effect of the cementitious pore-water from a repository on the surrounding rock. It should be noted that several of the quantities that the models predict (such as porosity, mineral masses dissolved or precipitated as a function of position in the column) are not readily measured accurately, and may be only available as a qualitative description. Other quantities that can be measured relatively accurately, such as the chemical composition of the out-flowing fluids, are values that represent an integration of the interactions taking place along the whole column. 

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