A continuum model for water movement in an unsaturated fractured rock mass

The movement of fluids in a fractured, porous medium has been the subject of considerable study. This paper presents a continuum model that may be used to evaluate the isothermal movement of water in an unsaturated, fractured, porous medium under slowly changing conditions. This continuum model was developed for use in evaluating the unsaturated zone at the Yucca Mountain site as a potential repository for high-level nuclear waste. Thus its development has been influenced by the conditions thought to be present at Yucca Mountain. A macroscopic approach and a microscopic approach are used to develop a continuum model to evaluate water movement in a fractured rock mass. Both approaches assume that the pressure head in the fractures and the matrix are identical in a plane perpendicular to flow. Both approaches lead to a single-flow equation for a fractured rock mass. The two approaches are used to calculate unsaturated hydrologic properties, i.e., relative permeability and saturation as a function of pressure head, for several types of tuff underlying Yucca Mountain, using the best available hydrologic data for the matrix and the fractures. Rock mass properties calculated by both approaches are similar.

[1]  R. L. Williams,et al.  Three-dimensional model of reference thermal/mechanical and hydrological stratigraphy at Yucca Mountain, southern Nevada , 1985 .

[2]  Daniel Hillel,et al.  Introduction to soil physics , 1982 .

[3]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[4]  Allen F. Moench,et al.  Double‐Porosity Models for a Fissured Groundwater Reservoir With Fracture Skin , 1984 .

[5]  H. J. Ramey,et al.  Unsteady-State Pressure Distributions Created by a Well With a Single Horizontal Fracture, Partial Penetration, or Restricted Entry , 1974 .

[6]  L. A. Richards.  Capillary conduction of liquids through porous mediums , 1931 .

[7]  J. R. Erickson,et al.  Identification and characterization of hydrologic properties of fractured tuff using hydraulic and tracer tests, test well USW H-4, Yucca Mountain, Nye County, Nevada , 1985 .

[8]  A. S. Odeh,et al.  Unsteady-State Behavior of Naturally Fractured Reservoirs , 1965 .

[9]  J. R. Gilman.  An Efficient Finite-Difference Method for Simulating Phase Segregation in the Matrix Blocks in Double-Porosity Reservoirs , 1986 .

[10]  J. O. Duguid,et al.  Water movement through saturated-unsaturated porous media: a finite- element Galerkin model , 1975 .

[11]  D. T. Snow,et al.  The frequency and apertures of fractures in rock , 1970 .

[12]  T. N. Narasimhan,et al.  A PRACTICAL METHOD FOR MODELING FLUID AND HEAT FLOW IN FRACTURED POROUS MEDIA , 1985 .

[13]  D. Mctigue,et al.  An Effective Stress Principle for Partially Saturated Granular Media , 1982 .

[14]  L. Gournay,et al.  Pore Size Distribution of Petroleum Reservoir Rocks , 1950 .

[15]  L. K. Thomas,et al.  Fractured Reservoir Simulation , 1980 .

[16]  G. I. Barenblatt,et al.  Basic concepts in the theory of seepage of homogeneous liquids in fissured rocks [strata] , 1960 .

[17]  J. E. Warren,et al.  The Behavior of Naturally Fractured Reservoirs , 1963 .

[18]  J. Sharp,et al.  Fluid flow through fissured media , 1970 .

[19]  I. J. Hall,et al.  Fracture and matrix hydrologic characteristics of tuffaceous materials from Yucca Mountain, Nye County, Nevada , 1984 .

[20]  W. E. Wilson,et al.  Conceptual hydrologic model of flow in the unsaturated zone, Yucca Mountain, Nevada , 1984 .

[21]  Doe.  ENVIRONMENTAL ASSESSMENT OVERVIEW YUCCA MOUNTAIN SITE, NEVADA RESEARCH AND DEVELOPMENT AREA, NEVADA , 1986 .

[22]  A. Corey.  Mechanics of Immiscible Fluids in Porous Media , 1986 .

[23]  T. N. Narasimhan,et al.  Hydrologic mechanisms governing partially saturated fluid flow in fractured welded units and porous non-welded units at Yucca Mountain , 1986 .

[24]  E. A. Klavetter,et al.  Estimation of hydrologic properties of an unsaturated, fractured rock mass , 1986 .

[25]  Humberto L. Najurieta,et al.  A Theory for Pressure Transient Analysis in Naturally Fractured Reservoirs , 1980 .

[26]  Y. Mualem.  A New Model for Predicting the Hydraulic Conductivity , 1976 .

[27]  T. D. Streltsova-Adams.  Well Hydraulics in Heterogeneous Aquifer Formations , 1978 .

[28]  Benjamin Ross.  A conceptual model of deep unsaturated zones with negligible recharge , 1984 .

[29]  T. N. Narasimhan,et al.  Hydrologic Mechanisms Governing Fluid Flow in a Partially Saturated, Fractured, Porous Medium , 1985 .

[30]  N. T. Burdine.  Relative Permeability Calculations From Pore Size Distribution Data , 1953 .

[31]  W. R. Purcell,et al.  Capillary Pressures - Their Measurement Using Mercury and the Calculation of Permeability Therefrom , 1949 .

[32]  T. N. Narasimhan,et al.  Physics of saturated-unsaturated subsurface flow , 1982 .

[33]  James O. Duguid,et al.  Flow in fractured porous media , 1977 .