- Email: [email protected]
The potential of SF6 as a geothermal tracer
12A
HYDROGEOLOGY:FLUID PRESSURE
The Boundary-Fitted Coordinate (BFC) Transformation method is a very powerful, efficient and accurate method of modeling heat or fluid flow in two- or three-dimensional domains with complex boundary shapes and abrupt changes in internal properties. The BFC transformation method was employed to simulate two hypothetical well-flow scenarios in isotropic and anisotropic domains, and actual groundwater flows in the area of West Lafayette, Indiana. The numerical solutions in those cases were at least as accurate as and/or consistent with those obtained by purely finite difference and finite element methods, but with the added advantage of more accurate representation and implementation of the boundary condition in the region of great sensitivity. (from Authors) 961091 Experimental tests using Rhodamine Wt as tracer A. di Fazio & M. Vurro, Advances in Water Resources, 17(6), 1994, pp 375-378. Tracer tests with fluorescent dyes have been commonly used to describe physical mechanisms and consequently to determine hydrodispersive parameters. The actual bebaviour of these dyes is one of the central issues in the evaluation of tracer tests. This paper describes an experimental set-up designed to investigate the behaviour of Rhodamine Wt. The tests reveal a mild nonlinear sorption behaviour of Rhodamine Wt. The experimental tests have also pointed out the feasibility of the mathematical model used to calibrate the experimental data. (from Authors) 961092 The potential of SF6 as a geothermal tracer R. C. Upstill-Goddard & C. S. Wilkins, Water Research, 29(4), 1995, pp 1065-1068. A novel application of gaseous sulphur hexafluoride (SF6) tracer, in the evaluation of bulk water flow through an artificial geothermal reservoir, the Hot Dry Rock (HDR) reservoir at Rosemanowes quarry, south west England, is described. In a 52 h continuous borehole pumping test in the H D R reservoir, SF6 and sodium fluorescein (N_aFl) were injected simultaneously in a mass ratio of 7.5 x 10.7 SF6:NaFI and analysed in production well waters. Resultant tracer response curves demonstrate conservation of the injected tracer mass ratio throughout the first 25 h of the test. However, substantial divergence of the curves beyond 25 h reflects significant tracer fractionation, most probably a consequence of selective diffusion and enhanced SF6 residence times in some of the longer residence time flow paths of the system. These results indicate the strong potential of SF6 as a water tracer. (from Authors) 961093 Double-diffusion from a vertical surface in a porous region saturated with a non-Newtonian fluid S. K. Rastogi & D. Poulikakos, International Journal of Heat & Mass Transfer, 38(5), 1995, pp 935-946. In this paper, a theoretical study is presented for the problem of double-diffusion from a vertical plate embedded in a porous matrix that is saturated with a non-Newtonian (power law) fluid. The study consists of two parts: In the first part, scaring analysis is utilized to obtain estimates of the quantities of interest and to identify the various possible flow regimes depending on the values of the buoyancy ratio and the Lewis number. In the second part numerical solution of the problem is presented for the general case of a wall with arbitrarily varying temperature and concentration. (from Authors) 961094 Water movement in desert soil traced by hydrogen and oxygen isotopes, chloride, and chlorine-36, southern Arizona Beiling Liu, F. Phillips, S. Hoines, A. R. Campbell & P. Sbarma, Journal of Hydrology, 168(1-4), 1995, pp 91-110. Seasonal soil water movement in the top meter of undisturbed desert soil in the southern Arizona was investigated using 2H, 1So, CI, and bomb-36Cl. Six soil profiles were sampled from a
young terrace (Holocene) during 1991 to 1992 on a seasonal basis. One soil profile was sampled from an older terrace (latest Pleistocene) in October 1992, and one from a yet older fan surface (late Pleistocene) in March 1992. The results indicate that repeated seasonal cyclic movement of soil water in the top 60-80 em active zone tends to produce a consistent stable isotope composition for the soil water below the active zone in different seasons. The correlation between the deep 61SO, the reduction of downward flux and the surface age suggests that increasing soil development has resulted in a significant decrease of soil water infiltration and hence an increase in evaporation and surface runoff. (from Authors) 961095 Relations of borehole resistivity to the horizontal hydraulic conductivity and dissolved-solids concentration in water of elastic coastal plain aquifers in the southeastern United States R. E. Faye & W. G. Smith, US Geological Survey WaterSupply Paper, 2414, 1994, 33 pp. Aquifer bulk resistivity and grain-surface resistivity (inverse of grain-surface conductance) were tested as geoelectdeal analogs to the horizontal hydraulic conductivity of elastic, freshwater aquifers in the Southeastern US. Aquifer bulk resistivity and grain-surface resistivity were moderately correlated to horizontal hydraulic conductivity (70 and 72% correlation coefficients, respectively). Apparent formation factor, defined as the ratio of aquifer bulk resistivity to aquifer water resistivity, was shown to be poorly correlated with horizontal hydraulic conductivity (38% correlation coefficient). Aquifer bulk resistivity was shown to be highly correlated with dissolved-solids concentration and aquifer water resistivity (88 and 93% correlation coefficients, respectively). Regression models using bulk resistivity amd aquifer water resistivity as independent variables were applied at four locations in South Carolina and Louisiana to predict dissolved-solids concentrations in aquifer water. (from Authors) 961096 Estimation of vertical water and heat fluxes in the semiconfined aquifers in Tokyo metropolitan area, Japan S. Dapaah-Siakwan & I. Kayane, Hydrological Processes, 9(2), 1995, pp 143-160. Heat transport in groundwater systems is considered to be a coupled process and the theory based on this was used to analyse temperature profiles of 30 thermally stable observation wells in a deep, semi-confined aquifer system in the Tokyo Metropolitan area. Vertical water fluxes in the semiconfined aquifers and the associated upward heat fluxes were estimated from a heat flux equation that describes convection and conduction processes of heat transport in one dimension. The water flux generally decreased with increasing depth for observation wells which intercepted more than one semiconfined layer. The heat flux was highest in Tachikawa terrace where a major fault, the Tachikawa fault, is located. Generally, the estimated heat flux was higher in the semiconfining layers than in the aquifers. (from Authors) 961097 Thermal venting to recovery less-volatile hydrocarbons from the unsaturated zone, 1. Theory J. J. Kaluarachchi & K. M. M.-U. Islam, Journal of Contaminant Hydrology, 17(4), 1995, pp 293-311. Thermal venting is a remediation technique suitable to the liquid unsaturated zone to enhance recovery of less-volatile residual hydrocarbon contaminants. Thermal venting is different to traditional soil venting because heated air instead of air at ambient conditions is applied to the contaminated zone. The vapor pressure of a less-volatile contaminant is typically increased by temperature causing the gas-phase concentrations to increase by three-to five-fold over a temperature increase of 20-30°C. The work described in this first paper provides the theoretical framework of analysis related to thermal venting. The analysis included noniso-
HYDROGEOLOGY:FLUID PRESSURE
The Boundary-Fitted Coordinate (BFC) Transformation method is a very powerful, efficient and accurate method of modeling heat or fluid flow in two- or three-dimensional domains with complex boundary shapes and abrupt changes in internal properties. The BFC transformation method was employed to simulate two hypothetical well-flow scenarios in isotropic and anisotropic domains, and actual groundwater flows in the area of West Lafayette, Indiana. The numerical solutions in those cases were at least as accurate as and/or consistent with those obtained by purely finite difference and finite element methods, but with the added advantage of more accurate representation and implementation of the boundary condition in the region of great sensitivity. (from Authors) 961091 Experimental tests using Rhodamine Wt as tracer A. di Fazio & M. Vurro, Advances in Water Resources, 17(6), 1994, pp 375-378. Tracer tests with fluorescent dyes have been commonly used to describe physical mechanisms and consequently to determine hydrodispersive parameters. The actual bebaviour of these dyes is one of the central issues in the evaluation of tracer tests. This paper describes an experimental set-up designed to investigate the behaviour of Rhodamine Wt. The tests reveal a mild nonlinear sorption behaviour of Rhodamine Wt. The experimental tests have also pointed out the feasibility of the mathematical model used to calibrate the experimental data. (from Authors) 961092 The potential of SF6 as a geothermal tracer R. C. Upstill-Goddard & C. S. Wilkins, Water Research, 29(4), 1995, pp 1065-1068. A novel application of gaseous sulphur hexafluoride (SF6) tracer, in the evaluation of bulk water flow through an artificial geothermal reservoir, the Hot Dry Rock (HDR) reservoir at Rosemanowes quarry, south west England, is described. In a 52 h continuous borehole pumping test in the H D R reservoir, SF6 and sodium fluorescein (N_aFl) were injected simultaneously in a mass ratio of 7.5 x 10.7 SF6:NaFI and analysed in production well waters. Resultant tracer response curves demonstrate conservation of the injected tracer mass ratio throughout the first 25 h of the test. However, substantial divergence of the curves beyond 25 h reflects significant tracer fractionation, most probably a consequence of selective diffusion and enhanced SF6 residence times in some of the longer residence time flow paths of the system. These results indicate the strong potential of SF6 as a water tracer. (from Authors) 961093 Double-diffusion from a vertical surface in a porous region saturated with a non-Newtonian fluid S. K. Rastogi & D. Poulikakos, International Journal of Heat & Mass Transfer, 38(5), 1995, pp 935-946. In this paper, a theoretical study is presented for the problem of double-diffusion from a vertical plate embedded in a porous matrix that is saturated with a non-Newtonian (power law) fluid. The study consists of two parts: In the first part, scaring analysis is utilized to obtain estimates of the quantities of interest and to identify the various possible flow regimes depending on the values of the buoyancy ratio and the Lewis number. In the second part numerical solution of the problem is presented for the general case of a wall with arbitrarily varying temperature and concentration. (from Authors) 961094 Water movement in desert soil traced by hydrogen and oxygen isotopes, chloride, and chlorine-36, southern Arizona Beiling Liu, F. Phillips, S. Hoines, A. R. Campbell & P. Sbarma, Journal of Hydrology, 168(1-4), 1995, pp 91-110. Seasonal soil water movement in the top meter of undisturbed desert soil in the southern Arizona was investigated using 2H, 1So, CI, and bomb-36Cl. Six soil profiles were sampled from a
young terrace (Holocene) during 1991 to 1992 on a seasonal basis. One soil profile was sampled from an older terrace (latest Pleistocene) in October 1992, and one from a yet older fan surface (late Pleistocene) in March 1992. The results indicate that repeated seasonal cyclic movement of soil water in the top 60-80 em active zone tends to produce a consistent stable isotope composition for the soil water below the active zone in different seasons. The correlation between the deep 61SO, the reduction of downward flux and the surface age suggests that increasing soil development has resulted in a significant decrease of soil water infiltration and hence an increase in evaporation and surface runoff. (from Authors) 961095 Relations of borehole resistivity to the horizontal hydraulic conductivity and dissolved-solids concentration in water of elastic coastal plain aquifers in the southeastern United States R. E. Faye & W. G. Smith, US Geological Survey WaterSupply Paper, 2414, 1994, 33 pp. Aquifer bulk resistivity and grain-surface resistivity (inverse of grain-surface conductance) were tested as geoelectdeal analogs to the horizontal hydraulic conductivity of elastic, freshwater aquifers in the Southeastern US. Aquifer bulk resistivity and grain-surface resistivity were moderately correlated to horizontal hydraulic conductivity (70 and 72% correlation coefficients, respectively). Apparent formation factor, defined as the ratio of aquifer bulk resistivity to aquifer water resistivity, was shown to be poorly correlated with horizontal hydraulic conductivity (38% correlation coefficient). Aquifer bulk resistivity was shown to be highly correlated with dissolved-solids concentration and aquifer water resistivity (88 and 93% correlation coefficients, respectively). Regression models using bulk resistivity amd aquifer water resistivity as independent variables were applied at four locations in South Carolina and Louisiana to predict dissolved-solids concentrations in aquifer water. (from Authors) 961096 Estimation of vertical water and heat fluxes in the semiconfined aquifers in Tokyo metropolitan area, Japan S. Dapaah-Siakwan & I. Kayane, Hydrological Processes, 9(2), 1995, pp 143-160. Heat transport in groundwater systems is considered to be a coupled process and the theory based on this was used to analyse temperature profiles of 30 thermally stable observation wells in a deep, semi-confined aquifer system in the Tokyo Metropolitan area. Vertical water fluxes in the semiconfined aquifers and the associated upward heat fluxes were estimated from a heat flux equation that describes convection and conduction processes of heat transport in one dimension. The water flux generally decreased with increasing depth for observation wells which intercepted more than one semiconfined layer. The heat flux was highest in Tachikawa terrace where a major fault, the Tachikawa fault, is located. Generally, the estimated heat flux was higher in the semiconfining layers than in the aquifers. (from Authors) 961097 Thermal venting to recovery less-volatile hydrocarbons from the unsaturated zone, 1. Theory J. J. Kaluarachchi & K. M. M.-U. Islam, Journal of Contaminant Hydrology, 17(4), 1995, pp 293-311. Thermal venting is a remediation technique suitable to the liquid unsaturated zone to enhance recovery of less-volatile residual hydrocarbon contaminants. Thermal venting is different to traditional soil venting because heated air instead of air at ambient conditions is applied to the contaminated zone. The vapor pressure of a less-volatile contaminant is typically increased by temperature causing the gas-phase concentrations to increase by three-to five-fold over a temperature increase of 20-30°C. The work described in this first paper provides the theoretical framework of analysis related to thermal venting. The analysis included noniso-