A constitutive model for water flow in unsaturated fractured rocks

Guarracino, Luis; Quintana, Fernando A.

doi:10.1002/hyp.7169

Cited by 13 publications

(9 citation statements)

References 23 publications

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“…In view of all this, it is reasonable to represent fractures as parts of the poroelastic continuum. Indeed, this conceptualization is consistent with the models proposed by Liu et al [2000] for describing the effective elastic properties of fractured rocks and is commonly employed to simulate groundwater flow in fractured media [e.g., Liu and Bodvarsson, 2001;Guarracino and Quintana, 2009].…”

Section: Discussionmentioning

confidence: 99%

Seismoacoustic signatures of fracture connectivity

et al. 2014

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Wave-induced fluid flow (WIFF) between fractures and the embedding matrix as well as within connected fractures tends to produce significant seismic attenuation and velocity dispersion. While WIFF between fractures and matrix is well understood, the corresponding effects related to fracture connectivity and the characteristics of the energy dissipation due to flow within fractures are largely unexplored. In this work, we use oscillatory relaxation simulations based on the quasi-static poroelastic equations to study these phenomena. We first consider synthetic rock samples containing connected and unconnected fractures and compute the corresponding attenuation and phase velocity. We also determine the relative fluid displacement and pressure fields in order to gain insight into the physical processes involved in the two manifestations of WIFF in fractured media. To quantify the contributions of the two WIFF mechanisms to the total seismic attenuation, we compute the spatial distribution of the local energy dissipation. Finally, we perform an exhaustive sensitivity analysis to study the role played by different characteristics of fracture networks on the seismic signatures. We show that in the presence of connected fractures both P wave attenuation and phase velocity are sensitive to some key characteristics of the probed medium, notably to the lengths, permeabilities, and intersection angles of the fractures as well as to the overall degree of connectivity of the fracture network. This, in turn, indicates that a deeper understanding of these two manifestations of WIFF in fractured media may eventually allow for the extraction of some of these properties from seismic data.

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Section: Discussionmentioning

confidence: 99%

Seismoacoustic signatures of fracture connectivity

et al. 2014

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“…The porosity and permeability of the porous media are estimated using an equivalent medium theory. This geometrical description of the porous media and upscaling procedure has been successfully used to describe water flow in fractured media (Guarracino, 2006;Guarracino & Quintana, 2009), the evolution of multiphase flow properties during mineral dissolution (Guarracino et al, 2014), and relations between hydraulic parameters (Guarracino, 2007). On the other hand, the effective excess charge in a single tube can be calculated from the radial distributions of excess charge and water velocity.…”

Section: 1002/2017jb014873mentioning

confidence: 99%

A Physically Based Analytical Model to Describe Effective Excess Charge for Streaming Potential Generation in Water Saturated Porous Media

2018

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Among the different contributions generating self‐potential, the streaming potential is of particular interest in hydrogeology for its sensitivity to water flow. Estimating water flux in porous media using streaming potential data relies on our capacity to understand, model, and upscale the electrokinetic coupling at the mineral‐solution interface. Different approaches have been proposed to predict streaming potential generation in porous media. One of these approaches is the flux averaging which is based on determining the excess charge which is effectively dragged in the medium by water flow. In this study, we develop a physically based analytical model to predict the effective excess charge in saturated porous media using a flux‐averaging approach in a bundle of capillary tubes with a fractal pore size distribution. The proposed model allows the determination of the effective excess charge as a function of pore water ionic concentration and hydrogeological parameters like porosity, permeability, and tortuosity. The new model has been successfully tested against different set of experimental data from the literature. One of the main findings of this study is the mechanistic explanation to the empirical dependence between the effective excess charge and the permeability that has been found by several researchers. The proposed model also highlights the link to other lithological properties, and it is able to reproduce the evolution of effective excess charge with electrolyte concentrations.

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“…The water relative permeability (k rw ) for the fractured rock can be predicted from a simple relation derived by Liu and Bodvarsson. However, the conceptual model 21 contains three empirical constants which are only valid under given assumptions. In addition, Kuang and Jiao 22 proposed a model for predicting relative nonwetting phase permeability from soil water retention curves.…”

Section: Introductionmentioning

confidence: 99%

A Fractal Model for Water Flow Through Unsaturated Porous Rocks

et al. 2018

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In this work, considering the effect of porosity, pore size, saturation of water and tortuosity fractal dimension, an analytical model for the capillary pressure and water relative permeability is derived in unsaturated porous rocks. Besides, the formulas of calculating the capillary pressure and water relative permeability are given by taking into account the fractal distribution of pore size and tortuosity of capillaries. It can be seen that the capillary pressure for water phase decreases with the increase of saturation in unsaturated porous rocks. It is found that the capillary pressure for water phase decreases as the tortuosity fractal dimension decreases. It is further seen that the capillary pressure for water phase increases with the decrease of porosity, and at low porosity, the capillary pressure increases sharply with the decrease of porosity. Besides, it can be observed that the water relative permeability increases with the increase of saturation in unsaturated porous rocks. This predicted the capillary pressure and water relative permeability of unsaturated porous rocks based on the proposed models which are in good agreement with the experimental data and model predictions reported in the literature. § Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1840015-1 B. Xiao et al.The proposed model improved the understanding of the physical mechanisms of water flow through unsaturated porous rocks.

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A constitutive model for water flow in unsaturated fractured rocks

Cited by 13 publications

References 23 publications

Seismoacoustic signatures of fracture connectivity

Seismoacoustic signatures of fracture connectivity

A Physically Based Analytical Model to Describe Effective Excess Charge for Streaming Potential Generation in Water Saturated Porous Media

A Fractal Model for Water Flow Through Unsaturated Porous Rocks

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