ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00773.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTA comparison of the aquifer parameter values obtained through the analysis of a local and a regional aquifer test involving the same area in southeast Georgia is made in order to evaluate the validity of extrapolating local aquifer‐test results for use in large‐scale flow simulations. The case study involves an increase in pumpage of 6.3 Mgal/d (million gallons per day) for the local test and a reduction in pumpage of 66 Mgal/d for the regional test, each involving the same well field. The test involved the Floridan aquifer system, a limestone sequence characterized predominantly by secondary permeability in this area. Time‐drawdown and time‐recovery data were analyzed by using both graphical and least‐squares fitting of the data to the Theis curve. Additionally, directional transmissivity, transmissivity tensor, and angle of anisotropy were computed for both tests. The major and minor axes of the transmissivity ellipse determined from the regional test show general agreement with those determined from the local test. A slightly higher ratio of anisotropy was observed on the regional scale: 2.1:1, than on the local scale: 1.5:1. Regional storage coefficients ranged from 3.4 × 10−4to 7.2 × 10−4as compared with local storage coefficients ranging from 1.8 × 1

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00774.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTMedina gas wells and oil wells in northwestern Pennsylvania, northeastern Ohio, and western New York create a potential for contamination of the fresh‐water aquifers that overlie the production zones of these wells. Most of these wells are constructed in a manner which results in an open annulus which is a few hundred to a few thousand feet long below the surface casing of the well. This annulus is a potential avenue of migration of contaminants from strata of higher hydrodynamic pressure into formations of lower hydrodynamic pressure. If gas from the strata exposed to the annulus is not permitted to escape to the atmosphere, the annulus may become pressurized, and a hydraulic gradient may be created between the potential contaminants in the annulus (e.g., brine and/or natural gas) and the overlying fresh‐water aquifers. If a permeability pathway exists between the pressurized annulus and an overlying fresh‐water aquifer, contamination of the aquifer will result.The risk of contaminating fresh ground water with the contents of a gas‐ or oil‐well annulus could be greatly reduced by filling the annulus with cement. An alternative precaution would be to operate the well in a manner that does not allow the annulus pressure to exceed the normal pressure of the formations exposed to th

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00775.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTOn the leeward side of southeastern Oahu, Hawaii, near‐vertical dikes have intruded the gently dipping and highly permeable lava flows of the Koolau mountain. These dikes bound the study area on the north and west and internally divide it into the Waialae and Wailupe‐Hawaii Kai aquifers. Recharge to these aquifers, 6 and 9 million gallons per day respectively, has created Ghyben‐Herzberg lenses that freely float on sea water and discharge to the sea through coastal sediments. In the Waialae area, where rainfall is high and where thick (poorly permeable) coastal sediments inhibit the discharge of fresh water, heads are 8 to 15 feet above sea level. Lower rainfall and thin coastal sediments that allow easy discharge cause heads to be only 1 to 5 feet in the Wailupe‐Hawaii Kai area.The flow of ground water and the effects of future water development were simulated using AQUIFEM, a two‐dimensional finite‐element flow model, modified for aquifers containing a sea‐water interface. The model provides accurate simulation of observed heads averaged over several years and predicts an additional area‐wide head decline of about 1 foot when three recently drilled wells are put

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00776.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTConceptualization of regional hydrogeologic setup in a hard rock granitic terrain by employing sparse data obtained through conventional methods is usually not possible. In such situations, aquifer simulation could be employed as a useful tool. An attempt was made to evolve the regional pattern of hydrogeologic parameters in a granitic basin. During the process of model calibration, the field estimates of hydrogeological parameters as well as those of recharge and ground‐water extraction were appropriately modified. A first‐order estimate of the effluent outflow from the aquifer to ephemeral streams was made only from the flow model. The calibrated model satisfactorily reproduced the historical response of the aquifer and could be used for progno

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00777.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThough flow nets offer one of the best means of visualizing ground‐water flow fields, accurate construction of flow nets can be very difficult in heterogeneous, anisotropic media or in regional cross sections where vertical exaggeration of scale is great. A method was developed for automatically generating the streamlines of a flow net using conventional ground‐water flow modeling algorithms. The method can be implemented using most any of the existing computer programs for flow modeling, and no modification of the programs is necessary. One need only replace the hydraulic head and conductivity terms in the steady‐state ground‐water flow equation with the stream function and an inverse form of hydraulic conductivity, respectively. Possible boundary conditions include prescribed stream function (Dirichlet type) and prescribed stream function gradient (Neumann type). The former can be determined from prior knowledge of recharge or discharge rates or from boundary fluxes computed in previous simulations of hydraulic head distribution. The latter can be determined from data on hydraulic head along the boundaries, raising the possibility of solving for the streamlines directly without first solving for the head distribution. The method is generally not appropriate when sources or sinks occur inside the flow region, and it will not handle transient conditions. Accuracy of the method is demonstrated in three hypothetical test problems and a vertical‐plane model through the Palo Duro Basin of Texas and N

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00778.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTApproximately half of the perimeters of Wyoming foreland artesian basins are characterized by structural continuity of the Paleozoic aquifers between the recharge areas and the interior parts of the artesian basins. A significant percentage of the ground water which circulates through such recharge areas is rejected through springs because there is a marked decrease in transmissivity basin‐ward from the recharge areas. The transmissivity contrasts have developed since the recharge areas became morphologically differentiated from the basin interiors during post‐Laramide time. Secondary enhancement of permeabilities is occurring in the recharge areas through dissolution of the rock matrix and cement, and in some locations the rocks were tectonically fractured. In contrast, the rates of dissolution within the basin interiors are substantially decreased, or processes of recrystallization, cementation, or compaction are operating to destroy permeability. The result is that in the case treated here, net recharge to the basin interior is a small fraction of measured stream losses in the headwaters of the recharge a

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00779.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTSamples for analysis of volatile organic compounds were collected from 315 wells in the Potomac‐Raritan‐Magothy aquifer system in southwestern New Jersey and a small adjacent area in Pennsylvania during 1980–82. Volatile organic compounds were detected in all three aquifer units of the Potomac‐Raritan‐Magothy aquifer system in the study area. Most of the contamination appears to be confined to the outcrop area at present. Low levels of contamination, however, were found downdip of the outcrop area in the upper and middle aquifers.Trichloroethylene, tetrachloroethylene, and benzene were the most frequently detected compounds. Differences in the areal distributions of light chlorinated hydrocarbons, such as trichloroethylene, and aromatic hydrocarbons, such as benzene, were noted and are probably due to differences in the uses of the compounds and the distribution patterns of potential contamination sources.The distribution patterns of volatile organic compounds differed greatly among the three aquifer units. The upper aquifer, which crops out mostly in less‐developed areas, had the lowest percentage of wells with volatile organic compounds detected (10 percent of wells sampled). The concentrations in most wells in the upper aquifer which had detectable levels were less than 10 /μg/1. In the middle aquifer, which crops out beneath much of the urban and industrial area adjacent to the Delaware River, detectable levels of volatile organic compounds were found in 22 percent of wells sampled, and several wells contained concentrations above 100 μ/1. The lower aquifer, which is confined beneath much of the outcrop area of the aquifer system, had the highest percentage of wells (28 percent) with detectable levels. This is probably due to (1) vertical leakage of contamination from the middle aquifer, and (2) the high percentage of wells tapping the lower aquifer in the most heavily developed areas o

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00780.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTWhen other wells are pumping from an aquifer in which a pumping test is being carried out, they can interfere with the observed data. Even if the interfering wells are several kilometers away, they can have a significant effect on test results. The effect of the interfering wells on the drawdown can be misinterpreted .as boundary effects. By combining the series expansions for the Theis expression for the pumped and interfering wells, it is shown that the magnitude of the interference depends primarily on the length of time for which the interfering well pumps before the start of the test. An important finding of the analysis is that the distance between the test and interfering wells has a small effect. A method of correcting for the effect of an interfering well during both pumping and recovery phases is introduced.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00781.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTWhile drillstem tests have been used extensively in the petroleum industry to obtain reliable measurements of hydraulic parameters in single boreholes, the technique has been used only to a limited extent in ground‐water investigations. This is due in part to the limited availability and high cost of suitable equipment for small‐diameter boreholes. In this study, drillstem tests were performed in exploratory boreholes to evaluate the hydraulic characteristics of a proposed compressed air energy storage site in central Illinois. The tests were conducted in small‐diameter coreholes (vertical and inclined) at depths up to 610 meters (2000 ft) using a drillstem tool designed and field‐tested by the authors. Field data were analyzed using semilog and curve‐matching techniques. Values of hydraulic conductivity obtained by the two methods were generally in very good agreement. The curve‐matching method allowed for calculation of wellbore storage and an estimation of well‐bore damage (skin effect). Test results indicate that exploratory boreholes were severely damaged by the coring process. In the presence of wellbore damage, slug test hydraulic conductivities were significantly lower than those given by drillstem tests conducted in the same zones. The sole use of slug tests would have underestimated hydraulic conductivity and led to erroneous conclusions regarding site conditions. The drillstem test methodology described herein offers a cost‐effective technique for measuring representative values of hydraulic conductivity in s

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb00782.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY