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Tracer experiments in fractured rocks: matrix diffusion and the validity of models
80A which leads to the exact results in I D and 2D cases but underestimates the nonlinear correction of effective conductivity for the 3D case.
942158 Variation in aperture estimation ratios from hydraulic and tracer tests in a single fracture Cady, C C; Silliman, S E; Shaffern, E Water Resour Res V29, N9. Sept 1993, P2975-2982
942154 Tracer experiments in fractured rocks: matrix diffusion and the validity of models Maloszweski, P; Zuber, A Water Resour Res V29, N8, Aug 1993, P2723-2735
Results from two concurrent hydraulic and tracer tests in the same fracture within a dolomite formation are used to derive aperture estimates. The tests were centred on the same well but performed in different principal directions. The ratio of aperture derived from the tracer test to that from the hydraulic test was greater than 1.0 in the first experiment, less than 1.0 in the second. Such results, not previously reported in the literature, are justified in discussion.
Published tracer test data are re-examined using the single fracture dispersion model, in which the fractured rock is represented by a single fracture and the tracer may diffuse into the matrix. This model is easily calibrated to yield equivalent or better fit to experimental results than does the original model assuming negligible matrix diffusion and requiring many more fitting parameters. Validations based on the values of physical parameters of the SFDM or on tests with two tracers of distinctly different coefficients of molecular diffusion are presented.
942155 Borehole field method to determine unsaturated hydraulic conductivity Shan, C; Stephens, D B Water Resour Res V29, N8, Aug 1993, P2763-2769 A practical field technique to determine unsaturated hydraulic conductivity of soils at discrete intervals over any depth using borehole tests is presented. Water is injected at a point and steady state pressure distribution surrounding the source is monitored. An analysis has been developed which can interpret either steady state pressure heads at several points resulting from one injection or pressure heads at a single point due to multiple injections. Excellent results have been obtained in silt, silt loam, and clay loam soils.
942156 Effect of mud penetration on borehole skin properties Abboud, N M; Corapeioglu, M Y Water Resour Res II29, N8. Aug 1993, P2941-2950 Clay particles from drilling fluids can form a filter cake (skin) on the walls of boreholes and migrate into the formation. Governing equations are developed at the macroscopic scale for concentration of the clay particles in the pore fluid, cake permeability, and sonic velocity. Particle deposition and erosion and effects of mud penetration on permeability surrounding the wellbore are examined.
942157 Micromodel studies of three-fluid porous media systems: pore scale processes relating to capillary pressure-saturation relationships Soil, W E; Celia, M A; Wilson, L J Water Resour Res V29, N9, Sept 1993, P2963-2974 A novel experimental approach using a 2-dimensional porous medium, prepared by etching channels representing the pore space into a set of glass plates, has been used, in conjunction with digital image analysis, to measure the three fluid capillary pressure-saturation relation and examine the flow behaviour at the pore level. The experiments were pressure controlled. Different orders of fluid infiltration with respect to permeability were studied. Results provide information on important pore-scale mechanisms.
942159 Percolation and permeability in partially structured networks Ewing, R P; Gupta, S C Water Resour Res II29, N9, Sept 1993, P3179-3188 Many porous geological materials show nonrandom arrangement of pores or pore domains (structure). The effects of different nonrandom arrangements of pore domains containing the largest pores on the percolation and flow properties of simulated porous media have been examined. The length and shapes of the clusters (structural elements) and the fraction of pore space occupied by them have been varied. Results should provide insight into features of preferential flow through macropores and wormholes.
942160 Permeability, groutability and hydraufic monitoring of large dam foundations Foyo, A Proc EUROCK'93, Lisbon, 21-24 June 1993 VI, P115-120. Publ Rotterdam: A A Balkema, 1993 Low pressure tests (LPT) replaced the conventional Lugeon test in weak, impervious foundations of the Ponga Dam in Spain (laminated slates and sandstones) and the Tepoa Dam in Mexico (inhomogeneous volcanics). Test procedures are described and pressure-flow rate graphs illustrated. Hydraulic fracturing phenomena were seen even at low pressures. Because of this it is suggested that hydraulic monitoring or seepage control by means of a drainage curtain be used for such foundations, with grouting only in local zones if seepage rates become dangerous.
942161 Hydromechanical modelling of rock fracture under normal stress (In French) Lin, J F; Baroudi, H; Piguet, J P Proc EUROCK'93, Lisbon, 21-24 June 1993 VI, P151-157. Publ Rotterdam." A A Balkema, 1993 A hydromechanical coupling model for a rock fracture under normal loading is presented. The geometry of the fracture void space was generated stochastically. Flow through the fracture aperture void is modelled using finite element analysis and the boundary element method is used to compute fracture normal displacement. Simulation results are illustrated.
942158 Variation in aperture estimation ratios from hydraulic and tracer tests in a single fracture Cady, C C; Silliman, S E; Shaffern, E Water Resour Res V29, N9. Sept 1993, P2975-2982
942154 Tracer experiments in fractured rocks: matrix diffusion and the validity of models Maloszweski, P; Zuber, A Water Resour Res V29, N8, Aug 1993, P2723-2735
Results from two concurrent hydraulic and tracer tests in the same fracture within a dolomite formation are used to derive aperture estimates. The tests were centred on the same well but performed in different principal directions. The ratio of aperture derived from the tracer test to that from the hydraulic test was greater than 1.0 in the first experiment, less than 1.0 in the second. Such results, not previously reported in the literature, are justified in discussion.
Published tracer test data are re-examined using the single fracture dispersion model, in which the fractured rock is represented by a single fracture and the tracer may diffuse into the matrix. This model is easily calibrated to yield equivalent or better fit to experimental results than does the original model assuming negligible matrix diffusion and requiring many more fitting parameters. Validations based on the values of physical parameters of the SFDM or on tests with two tracers of distinctly different coefficients of molecular diffusion are presented.
942155 Borehole field method to determine unsaturated hydraulic conductivity Shan, C; Stephens, D B Water Resour Res V29, N8, Aug 1993, P2763-2769 A practical field technique to determine unsaturated hydraulic conductivity of soils at discrete intervals over any depth using borehole tests is presented. Water is injected at a point and steady state pressure distribution surrounding the source is monitored. An analysis has been developed which can interpret either steady state pressure heads at several points resulting from one injection or pressure heads at a single point due to multiple injections. Excellent results have been obtained in silt, silt loam, and clay loam soils.
942156 Effect of mud penetration on borehole skin properties Abboud, N M; Corapeioglu, M Y Water Resour Res II29, N8. Aug 1993, P2941-2950 Clay particles from drilling fluids can form a filter cake (skin) on the walls of boreholes and migrate into the formation. Governing equations are developed at the macroscopic scale for concentration of the clay particles in the pore fluid, cake permeability, and sonic velocity. Particle deposition and erosion and effects of mud penetration on permeability surrounding the wellbore are examined.
942157 Micromodel studies of three-fluid porous media systems: pore scale processes relating to capillary pressure-saturation relationships Soil, W E; Celia, M A; Wilson, L J Water Resour Res V29, N9, Sept 1993, P2963-2974 A novel experimental approach using a 2-dimensional porous medium, prepared by etching channels representing the pore space into a set of glass plates, has been used, in conjunction with digital image analysis, to measure the three fluid capillary pressure-saturation relation and examine the flow behaviour at the pore level. The experiments were pressure controlled. Different orders of fluid infiltration with respect to permeability were studied. Results provide information on important pore-scale mechanisms.
942159 Percolation and permeability in partially structured networks Ewing, R P; Gupta, S C Water Resour Res II29, N9, Sept 1993, P3179-3188 Many porous geological materials show nonrandom arrangement of pores or pore domains (structure). The effects of different nonrandom arrangements of pore domains containing the largest pores on the percolation and flow properties of simulated porous media have been examined. The length and shapes of the clusters (structural elements) and the fraction of pore space occupied by them have been varied. Results should provide insight into features of preferential flow through macropores and wormholes.
942160 Permeability, groutability and hydraufic monitoring of large dam foundations Foyo, A Proc EUROCK'93, Lisbon, 21-24 June 1993 VI, P115-120. Publ Rotterdam: A A Balkema, 1993 Low pressure tests (LPT) replaced the conventional Lugeon test in weak, impervious foundations of the Ponga Dam in Spain (laminated slates and sandstones) and the Tepoa Dam in Mexico (inhomogeneous volcanics). Test procedures are described and pressure-flow rate graphs illustrated. Hydraulic fracturing phenomena were seen even at low pressures. Because of this it is suggested that hydraulic monitoring or seepage control by means of a drainage curtain be used for such foundations, with grouting only in local zones if seepage rates become dangerous.
942161 Hydromechanical modelling of rock fracture under normal stress (In French) Lin, J F; Baroudi, H; Piguet, J P Proc EUROCK'93, Lisbon, 21-24 June 1993 VI, P151-157. Publ Rotterdam." A A Balkema, 1993 A hydromechanical coupling model for a rock fracture under normal loading is presented. The geometry of the fracture void space was generated stochastically. Flow through the fracture aperture void is modelled using finite element analysis and the boundary element method is used to compute fracture normal displacement. Simulation results are illustrated.