•.
Prepared in cooperation with the University of Minnesota and the Minnesota Geological Survey
Cyclic Injection, Storage, and Withdrawal of Heated Water in a Sandstone Aquifer at St. Paul, Minnesota Analysis of Thermal Data and Non isothermal Modeling of Long-Term Test Cycles 1 and 2
U.S. Geological Survey Professional Paper 1530-C
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,. . ' ~......
U.S. Department of the Interior U.S. Geological Survey
Cyclic Injection, Storage, and Withdrawal of Heated Water in a Sandstone Aquifer at St. Paul, Minnesota
1 2 1 3 By G.N. DEILN , M.C. HOYER , T.A. WINTERSTEIN andR.T. MILLER Analysis of Thermal Data and Non isothermal Modeling of Long-Term Test Cycles 1 and 2
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1530-C
Prepared in cooperation with the University of Minnesota and the Minnesota Geological Survey
1 U.S. Geological Surrvey, Mounds View, Minnesota 2 University of Minnesota, Underground Space Center, Department of Civil Engineering, Minneapolis, Minnesota 3 Groundwater Investigations, Inc., Pine Bush, New York U.S. DEPARTMENT OF THE INTERIOR
Gale A. Norton, Secretary
U.S. GEOLOGICAL SURVEY
Charles G. Groat, Director
Use of brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.
Mound View, Minnesota, 2002
Library of Congress Cataloging in Publications Data Delin, G.N., Hoyer, M.C., Winterstein, T.A., and Miller, R.T Cyclic injection, storage, and withdrawal of heated water in a sandstone aquifer at St. Paul, Minnesota I G.N. Delin, M.C. Hoyer, T.A. Winterstein, and R.T. Miller. 80 p., 28 em.- (Analysis of thermal data and nonisothermal modeling of long-term test cycles 1 and 2) (U.S. Geological Survey Professional Paper; 1530-C) "Prepared in cooperation wth the University of Minnesota and the Minnesota Geological Survey." Includes bibliographic references (p. 79). ISBN 0-607-99152-6 Supt. of Docs. no.: 119.16: 1530-C 1. Hot-air heating. 2. Hot water. 3. Water-storage-Minnesota-St. Paul. 4. Aquifers-Minnesota-St. Paul. I. Univesity of Minnesota. II. Minnesota Geological Survey. Ill. Title. IV. Series. V. Series: U.S. Geological Survey professional paper; 1530-C. TH7602.M55 2002 92-23497 697'.4-dc20 CIP
For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225 CONTENTS
Abstract ...... 1 Introduction ...... 1 Purpose and scope ...... 3 Hydrogeologic setting ...... 3 Aquifer selection ...... 4 Description of test facility ...... 5 Long-term test cycles 1 and 2 ...... 7 Analysis of thermal data for long-term test cycles I and 2 ...... 11 Temperature as a function of time ...... II Temperature profiles ...... 3 8 Discussion of thermal data ...... 45 Nonisothermal modeling of long-term test cycles I and 2 ...... 45 Simulation of model anisotropy ...... 4 7 Discretization of aquifer system ...... :...... 47 Boundary and initial conditions ...... 48 Model calibration ...... 48 Analysis of simulations ...... 52 Summary ...... 78 References ...... 79
Illustrations
Figure I. Map and block diagram showing location and generalized schematic diagram of hydrogeology of the Aquifer Thermal-Energy Storage site ...... 2 2. Map showing plan view of the Aquifer Thermal Energy Storage site ...... 6 3. Schematic diagram of sites A and Bat the Aquifer Thermal-Energy Storage site ...... 7 4. Schematic section showing depths of screened intervals of observation wells, stratigraphy, and location of measurement points of the Aquifer Thermal-Energy Storage site ...... 8 5. Diagram showing model grid and position of observation wells at various depths ...... I 0 Figures 6-22. Graphs showing: 6. Temperatures at the wellhead in production well A during long-term test cycle I, November I984 through May I985 ...... I2 7. Temperatures in observation well AMI during long-term test cycle I, November I984 through May I985 ...... I4 8. Temperatures in observation well ASI during long-term test cycle I, November I984 through May I985 ...... I6 9. Temperatures in observation well AM2 during long-term test cycle I, November I984 through May I985 ...... 18 IO. Temperatures in observation well AM3 during long-term test cycle I, November I984 through May I985 ..... 20 Il. Temperatures in observation well AM4 during long-term test cycle I, November I984 through May I985 ..... 22 I2. Temperatures in production well A during long-term test cycle 2, October I986 through Aprili987 ...... 24 13. Temperatures in observation well AMI during long-term test cycle 2, October I986 through Aprill987 ...... 26 14. Temperatures in observation well AS 1 during long-term test cycle 2, October 1986 through April 1987 ...... 28 15. Temperatures in observation well AM2 during long-term test cycle 2, October 1986 through April1987 ...... 30 16. Temperatures in observation well AM3 during long-term test cycle 2, October 1986 through April1987 ...... 32 I7. Temperatures in observation well AM4 during long-term test cycle 2, October 1986 through Aprili987 ...... 34 I8. Temperatures measured in observation well AMI at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 40 I9. Temperatures measured in observation well AS I at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 41
III Illustrations-Continued
20. Temperatures measured in observation well AM2 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 42 21. Temperatures measured in observation well AM3 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 43 22. Temperatures measured in observation well AM4 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 44 Figures 23-24. Diagrams showing: 23. Model grid and flow net for the Ironton and Galesville Sandstones near production well A for the long-term test cycles ...... 49 24. Model grid and flow net for the upper part of the Franconia Formation near production well A for the long-term test cycles ...... 50 Figures 25-36. Graphs showing: 25. Model-computed and measured temperatures at production well A during long-term test cycle 1 ...... 54 26. Model-computed and average measured temperatures in observation well AMl during long-term test cycle 1 ...... 56 27. Model-computed and average measured temperatures in observation well AS 1 during long-term test cycle 1 ...... 58 28. Model-computed and average measured temperatures in observation well AM2 during long-term test cycle 1 ...... 60 29. Model-computed and average measured temperatures in observation well AM3 during long-term test cycle 1 ...... 62 30. Model-computed and averaged measured temperatures in observation well AM4 during long-term test cycle 1 ...... 64 31. Model-computed and measured temperatures in production well A during long-term test cycle 2 ...... 66 32. Model-computed and averaged measured temperatures in observation well AMl during long-term test cycle 2 ...... 68 33. Model-computed and average measured temperatures in observation well ASl during long-term test cycle 2 ...... 70 34. Model-computed and average measured temperatures in observation well AM2 during long-term test cycle 2 ...... 72 35. Model-computed and average measured temperatures in observation well AM3 during long-term test cycle 2 ...... 7 4 36.Model-computed and average measured temperatures in observation well AM4 during long-term test cycle 2 ...... 76
Tables
Table 1. Summary of duration, average rates of injection and withdrawal, and average temperatures of injection, storage, and withdrawal for long-term test cycles 1 and 2 ...... 11 2. Temperature front arrival time at measurement points in the upper part of the Franconia Formation and in the Ironton and Galesville Sandstones for long term test cyclfs 1 and 2 ...... 36 3. Comparison of model-computed thermal efficiencies of the aquifer and final withdrawal-water temperatures at production well A with corresponding calculated and measured values for long-term test cycles 1 and 2 ...... 46 4. Layer number, thickness, and corresponding stratigraphic/hydrogeologic unit for the three-dimensional model ...... 51 5. Thermal properties used for simulation of the long-term test cycles 1 and 2 ...... 51 6. Hydraulic properties used for simulation of the long-term test cycles ...... 52 7. Summary of long-term test cycles 1 and 2 simulation times, durations, flow rates, and temperatures ...... 53 8. Altitudes of measurement points where temperatures were averaged to correspond with model layers ...... 78
IV CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS
Multiply By To obtain Length meter (m) 3.281 foot Area 2 square meter (m ) 0.0002471 acre Volume cubic meter (m3) 6.290 barrel (petroleum, 1 barrel=42 gal) Flow rate meter per day (m/d)) 3.281 foot per day cubic meter per second (m3 /s) 35.31 cubic foot per second liter per second (Lis) 15.85 gallon per minute cubic meter per day (m3/d) 264.2 gallon per day Mass kilogram (kg) 2.205 pound avoirdupois Pressure kilopascal (kPa) 0.1450 pound-force per inch Density 3 kilogram per cubic meter (kg/m ) 0.06242 pound per cubic foot Energy joule 0.0000002 kilowatt-hour 2 watt per square meter (W/m ) 8.804 x w-5 British thermal unit per square foot per second watt per cubic meter (W/m3) 2.684 x w- 5 British thermal unit per cubic foot per second British thermal unit per foot Celsius per day per joule per meter per day per degree [((J/m)/d)/0 C] 1.605 x w-4 degree Fahrenheit joule per cubic meter per degree [(J/m3)/°C] 1.491 x w-5 British thermal unit per cubic pound avoirdupois per British thermal unit per pound avoirdupois per degree joule per kilogram per degree [(J/kg)/0 C] 2.388 x w-4 Fahrenheit Hydraulic conductivity meter per day (m/d) 3.281 foot per day Hydraulic gradient meter per kilometer (m/km) 5.27983 foot per mile Transmissivity meter squared per day (m2/d) 10.76 foot squared per day
Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F = (1.8 X °C) + 32
Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)-a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.
Altitude, as used in this report, refers to distance above or below sea level.
Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness [(ft3d)/ ft2]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience.
Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (j..LS/cm at 25 °C).
Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (J..lg/L).
2 NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for square hectometer (hm ) is restricted to the mea 3 surement of small land or water areas. Use of liter (L) as a special name for cubic decimeter (dm ) is restricted to the measure ment of liquids and gases. No prefix other than milli should be used with liter. Metric ton (t) as a name for megagram (Mg) should be restricted to commercial usage, and no prefixes should be used with it. v
Cyclic Injection, Storage, and Withdrawal of Heated Water in a Sandstone Aquifer at St. Paul, Minnesota Analysis of Thermal Data and Non isothermal Modeling of Long-Term Test Cycles 1 and 2
3 By G.N. Delin1, M.C. Moyer2, T.A. Winterstein1, and R.T. Miller ABSTRACT model was constructed to simulate the two long-term test cycles. The only model properties varied during In May 1980, the University of Minnesota began a model calibration were longitudinal and transverse project to evaluate the feasibility of storing heated water thermal dispersivities, which, for final calibration, were (150 degrees Celsius) in the Franconia-Ironton simulated as 3.3 and 0.33 meters, respectively. The Galesville aquifer (183 to 245 meters below land model was calibrated by comparing model-computed surface) and later recovering it for space heating. The results to: (1) measured temperatures at selected University's steam-generation facilities supplied high altitudes in five observation wells, (2) measured temperature water for injection. This Aquifer Thermal temperatures at the production well, and (3) calculated Energy Storage system had a doublet-well design in thermal efficiencies of the aquifer. Model-computed which the injection and withdrawal wells were spaced withdrawal-water temperatures were within about 3 approximately 250 meters apart. Water was pumped percent of measured values and model-computed from one of the wells through a heat exchanger, where aquifer-thermal efficiencies were within about 1 heat was added or removed. This water was then percent of calculated values for the long-term test injected back into the aquifer through the other well. cycles. On the basis of these data, the model accurately Two long-term test cycles, consisting of simulates aquifer thermal-energy storage within the approximately equal durations of injection, storage and Franconia-Ironton-Galesville aquifer. withdrawal of about 59 days, were completed. Rates of injection and withdrawal of about 18 liters per second INTRODUCTION were maintained for each long-term test cycle. Injection The University of Minnesota started a project in May temperatures averaged about 108.5 and 117.7 degrees 1980 to evaluate use of a confined, sedimentary Celsius for long-term test cycles 1 and 2, respectively. bedrock (sandstone) aquifer [about 183 m beneath the Withdrawal temperatures averaged about 75 and 85 St. Paul campus] for thermal-energy storage (fig. 1). degrees Celsius, respectively. The project was funded by the U.S. Department of Temperature graphs for selected depths at individual Energy through Battelle Pacific Northwest observation wells indicate that the Ironton and Laboratories. Other participants in the project include Galesville Sandstones received, stored, and yielded the Minnesota Energy Agency, the Minnesota more thermal energy than the upper part of the Geological Survey, National Biocentrics, Inc., Orr Franconia Formation. Vertical-profile plots and time Schelen-Mayeron and Associates, and the U.S. graphs during storage indicate that the effects of Geological Survey. The project was designed to buoyancy flow were minimal within the aquifer. evaluate the feasibility and effects of storing high A three-dimensional, anisotropic, nonisothermal temperature (150°C) water in the Franconia-Ironton ground-water-flow and thermal-energy-transport Galesville aquifer beneath the St. Paul campus and later recovering the heat for water and space heating. The specific objectives of the U.S. Geological Survey 1 U.S. Geological Survey, Mounds View, Minnesota 2University of Minnesota, Underground Space Center, in evaluating Aquifer Thermal-Energy Storage (ATES) Depa1tment of Civil Engineering, Minneapolis, Minnesota were to: (1) develop an understanding of the ground 3Groundwater Investigations, Inc. , Pine Bush, New York water-flow system near the site, (2) identify the
Cl Building
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LOCATION MAP
Figure 1. Location and generalized schematic diagram of hydrogeology of the Aquifer Thermal-Energy Storage (ATES) site.
C2 hydraulic properties of the ground-water-flow system major regional aquifers. The aquifers generally are that are most important with respect to thermal-energy separated by semipermeable sandstone, siltstone, or storage and identify data-collection needs for shale formations. The major aquifers are the St. Peter, monitoring and evaluating aquifer-system Prairie du Chien-Jordan, Franconia-Ironton-Galesville, performance, (3) develop a method to evaluate flow and and Mount Simon-Hinckley-Fond duLac (fig. 1). thermal-energy transport for various cyclic injection The St. Peter aquifer consists of the St. Peter and withdrawal schemes and aid in selection of an Sandstone, which is composed of a light-yellow or efficient well-system design, and (4) assist in the white, massive, quartzose, fine- to medium-grained, collection of hydraulic and thermal data during well-sorted, and friable sandstone. Thin beds of injection-withdrawal tests and design a data-processing siltstone and shale near the base of the St. Peter system that will facilitate entry of the data into computer Sandstone form a lower confining layer. The upper storage. Miller (1984 and 1985) described the confining layer, consisting of the Platteville and anisotropy of the Franconia-Ironton -Gales ville aquifer, Glenwood Formations, overlies the St. Peter Sandstone and preliminary modeling at the ATES site, and is in contact with glacial drift. At the test site, the respectively. Miller and Voss (1986) described the St. Peter aquifer is approximately 57 m below land design of the finite-difference grid at the ATES site. surface and is 50 m thick. Transmissivity ranges from Miller and Delin (1993) described (1) analysis of field 220 to 280 m2/d and the storage coefficient ranges from observations for aquifer characterization and 5 3 observation-network design, (2) preliminary model 9.0 x 10 to 9.75 x 10 . Porosity ranges from 0.28 to analysis to determine model sensitivity to hydraulic and 0.30. The hydraulic gradient was estimated to be 0.006 thermal characteristics and to facilitate final model and the pore velocity was estimated to be 0.18 m/d by design, and (3) model simulations of the aquifer's Norvitch and others (1973). thermal efficiency. Miller and Delin ( 1994) described The Prairie du Chien-Jordan aquifer consists of the analysis of the thermal data and nonisothermal Prairie du Chien Group and the Jordan Sandstone (fig. modeling for the short-term test cycles. Walton and 1). The Prairie du Chien Group is predominantly a light others ( 1991) described the geologic and hydrologic brownish-gray or buff, sandy, thin- to thick-bedded setting of the ATES site, the ATES system and its dolomite that is vuggy and fractured and contains thin operation during the short-term test cycles, and layers of interbedded grayish-green shale. The presented the water chemistry, system flow, and underlying Jordan Sandstone is a white to yellow, temperature results for the short-term test cycles. Hoyer quartzose, fine-to coarse-grained sandstone that is and others (1991 a and 1991 b) describe additions to and massive or thick to thin bedded and varies from friable operation of the ATES system during the first and to well cemented. Despite the differing lithologies, the second long-term test cycles, and present the water Prairie du Chien Group and Jordan Sandstone function chemistry, system flow, and temperature results for the as one aquifer because there is no regional confining first and second long-term test cycles. unit between them. At the test site the aquifer is Purpose and Scope approximately 107 m below land surface and is 69 m thick. The average transmissivity is approximately This report describes (1) the collection of hydraulic 1,235 m2/d, with a porosity of 0.30. The hydraulic and thermal data for two long-term test cycles of heated gradient was estimated to be approximately 0.005 and water injection, storage, and withdrawal; and (2) the the pore velocity was estimated to be 0.30 m/d by analysis and nonisothermal modeling for the two Norvitch and Walton (1979). cycles. This report is one in a series that describes the potential for thermal-energy storage within the The St. Lawrence Formation acts as a confining layer Franconia-Ironton-Galesville aquifer beneath the St. between the Prairie du Chien-Jordan and the Franconia Paul campus of the University of Minnesota. Ironton Galesville aquifers. The St. Lawrence Formation is about 176m below land surface and is Hydrogeologic Setting approximately 7 m thick at the test site. It is a gray and The St. Paul metropolitan area is underlain by a greenish-gray, laminated, thin-bedded, dolomite stratified sequence of Proterozoic and early Paleozoic siltstone, silty dolomite, and shale. The porosity ranges sedimentary formations consisting of porous sandstone from 0.15 to 0.20 and transmissivities range from 1 to 10 2 and fractured dolomite, which can be grouped into four n1 /d.
C3 The Franconia-Ironton-Galesville aquifer consists of The Eau Claire Formation is a confining layer the Franconia Formation, and the Ironton and Galesville between the Franconia-Ironton Galesville and the Sandstones. The Franconia Formation is divided into Mount Simon-Hinckley-Fond duLac aquifers. The Eau four members: Reno, Mazomanie, Tomah, and Claire Formation consists of interbedded siltstone, Birkmose (Walton and others, 1991). The Reno shale, and fine silty sandstone with a few thin layers of Member in the upper part of the Franconia is a fine- to dolomite. The depth of the formation beneath the site is very fine-grained, quartz, and glauconitic sandstone. about 245 m and its thickness is about 29 m. 2 The Reno is divided into two sections and is located Transmissivity ranges from 0.5 to 5 m /d and porosity approximately between 180 and 183 m and between 193 ranges from 0.28 to 0.35 (Norvitch and others, 1973). and 206 m below land surface. The Mazomanie The Mount Simon-Hinckley-Fond duLac aquifer member is in the upper part of the Franconia between consists of the Mount Simon and Hinckley Sandstones the depths of 186-193 m. The Mazomanie also is a fine and the Fond du Lac Formation. The Mount Simon to very-fine grained, quartz sandstone, but has minor Sandstone is fine- to coarse-grained, contains very thin glauconite content. The Tomah Member in the lower beds of shale, and commonly is gray, white, or pink. part of the Franconia is an interbedded sequence of fine The Hinckley Sandstone is fine- to coarse-grained and to very fine-grained, silty sandstone with interbedded pale red to light pink. The Fond du Lac Formation siltstone or shale. The Tomah is located between 206 contains lenticular beds of fine- to medium-grained and 219 m below land surface. The Birkmose Member arkosic sandstone interbedded with mudstone and is in the lower part of the Franconia is a dolomitic siltstone dark red to pink. The top of the aquifer is approximately with some shale and fine- to very fine-grained 274m below land surface and the aquifer is approximately 60 m thick. The transmissivity is glauconitic sandstone interbedded. Based on laboratory approximately 250 m2/d and the storage coefficient is permeability tests (Walton and others, 1991), the about 6 x 105 (Norvitch and others, 1973). The porosity horizontal hydraulic conductivity of the upper part of averages 0.25, the hydraulic gradient is 0.0025, and the the Franconia is about 158 times greater than the pore velocity is approximately 0.03 m/d (Norvitch and hydraulic conductivity of the lower part of the others, 1973). Franconia. Analysis of results of packer tests indicate two hydraulic zones within the Franconia Formation Aquifer Selection (Miller and Delin, 1993). Based on the distinct The selection of an aquifer for thermal-energy testing differences in grain size, geophysical logs, and was based on the following criteria: (1) minimal use of hydraulic properties between the upper and lower parts water from the aquifer in the Twin Cities area, (2) ability of the Franconia Formation, the upper 14 m of the of the confining units above and below the aquifer to Franconia was considered an aquifer and the lower 25 m contain the injected heated water, and (3) the of the Franconia was considered a confining unit. The hydrogeologic properties and natural gradients within· Ironton Sandstone is white, medium-grained, the aquifer and their effect on the transfer of heat. moderately well-sorted quartz arenite that contains some silt -sized material. The Galesville Sandstone Description of Test Facility consists of a white to light-gray slightly glauconitic, The University of Minnesota test facility was a well- to moderately well-sorted, mostly medium doublet well system in which production wells A and B grained quartzose sandstone. The depth of the were spaced approximately 250m apart (fig. 2). During Franconia-Ironton -Galesville aquifer beneath the site is heat injection, water was pumped from the Franconia about 183 m and its thickness is about 62 m. The total Ironton-Galesville aquifer through production well B 2 transmissivity is 97.5 m /d and the storage coefficient is (fig. 2), transported through the ion-exchange water 5 2.75 x 10- . Transmissivity of the Franconia-Ironton softener where hardness was reduced, passed through a Galesville aquifer is anisotropic, with the principal axis heat exchanger where the water was heated, and of transmissivity oriented about 30 degrees east of injected back into the Franconia-Ironton-Galesville north. Average porosity ranges from 0.25 to 0.31 with aquifer through production well A (fig. 3). During heat a hydraulic gradient of 0.002 and an estimated pore withdrawal, water was pumped from the Franconia velocity of 0.05 m/d. The ambient temperature of the Ironton-Galesville aquifer through production well A ground-water system is typically about 11 °C. (fig. 2), transported through a radiator where the water
C4 Site C CM1
Site A
N AC1 AM3 (See Insert) A
U) ffi 1- UJ ::;;; 0 100 200 300 FEET 0 20 40 60 80 100 METERS
EXPLANATION • AM2 Observation well and identifier
Production well B
BS1 _j• ~ BC1 Site B
Figure 2. Plan view of the Aquifer Thermal-Energy Storage (ATES) sites.
cs was cooled, and then injected back into the aquifer figure 4. Individual thermocouples were coated with through production well B (fig. 3). The system also Teflon for resistance to heat, and each 4 or 8 included piping between the production wells, steam thermocouple string was covered with a stainless steel and condensate piping to the campus steam plant, heat overbraid to add rigidity and to protect each string as it exchangers, water treatment facility, observation wells, was lowered into the steel casing. During installation, and instrumentation (fig. 3). The production wells were however, the overbraid tended to twist and kink causing screened from about 40 to 61 m (Ironton and Galesville excessive wear to the thermocouple wire where the Sandstones) and from about 90 to 104m (upper part of kinks rubbed on the side of the well casing. Several the Franconia Formation) above sea level, respectively thermocouples failed because of electrical shorts in (fig. 4; Miller and Delio, 1993). For the long-term test thermocouple wires at these points of excessive wear. cycles an ion-exchange water softener was added to the Temperatures measured by the thermocouples probably system (fig. 3). were slightly less than the actual temperatures in the The ion-exchange water softener was added to the aquifer because of conductive heat losses to the well ATES system to prevent calcium carbonate casing; however, these temperature losses were precipitation in the storage well and aquifer, replacing minimal and measured temperatures were considered the above-ground precipitation filters that had been representative of temperatures in the aquifer. used during the short-term cycles (Walton and others, Submersible pressure transducers were installed to 1991 ; Miller and De lin, 1994 ). l'he ion-exchange water measure pressures in the observation wells. Pressures softener reduced the hardness of the ground water from 0 to 1,724 kPa could be measured in a temperature before it was heated, reducing the degree of scaling in range of 10-121 °C. Measurement accuracy was ±2 the heat exchangers and in the storage well (Hoyer and percent of the full-scale output over the compensated others, 199la and 199lb). Use of the water softener temperature range, or a maximum of ±34 kPa at 121 °C. allowed the uninterrupted operation of the ATES system The pressure transducers in most observation wells during heat injection (Hoyer and others, 1991 a and failed shortly after being installed. Several pressure 1991 b). During the short-term test cycles, the transducers were replaced more than once, only to fail precipitation filters and the heat exchangers required again. Only one pressure transducer functioned during cleaning after one or two days of injection (Walton and long-term test cycle 1 and none functioned during long others, 1991; Miller and Delio, 1994). term test cycle 2. Consequently, water levels were Temperature and pressure measurements were made measured periodically in the observation wells during in observation wells AMI, AM2, AM3, AM4, and AS I the long-term test cycles. Water-level data are reported (figs. 2 and 3). Observation well AM4 was installed in Hoyer and others (1991a and 199lb). 30.5 meters from production well A before the long term test cycles began to record temperatures near the All temperature and pressure-transducer data were anticipated maximum extent of the thennal front for the transmitted through buried cables to a central data long-term test cycles. Separate wells were installed for logger that measured data on electrostatic paper and temperature and pressure measurements at each nine-track computer tape. The operation of the data location (fig. 4). The altitudes of individual logger and the computer programs written to reduce the measurement points for the observation wells are also stored data are described in detail by Czarnecki (1983). shown in figure 4. Minor modification of the data-logger entries and the data-reduction program were required with the addition Temperature measurements at production well A of observation well AM4 for the long-term test cycles. were made by use of a type-T (copper-constantan) Some data were lost during the test cycles as a result of thermocouple installed within the injection/discharge occasional failure of individual data-logger channels. pipe at the wellhead. Temperature measurements within each of the observation wells (fig. 4) were made Individual data-collection points will be referred to in by use of as many as 12 type-T thermocouples as this report by their observation-well location with described in detail by Miller and Del in (1993). The respect to production well A and by their vertical thermocouples were in 1 or 2 manufactured strings (one position within each observation well as referenced to containing 8 thermocouples and one containing 4) in sea level. Reference to sea level as a datum is justified protective 3.2-cm- or 5.1-cm- diameter steel casings because over the very small area of the site, the within the observation wells at the altitudes shown in formations are essentially flat-lying.
C6 SITE A
AMl• TRAILER (/) cc LJ.J Data recording, r- Production LJ.J fie ld laboratory, :;',! Well A ..... and fie ld office 14 METERS AM21< ~ >0. • <--- - <- --- ')~
~> ~1 ~ ..;, r- U' - ,-----c:j" LJ.J :;',! Jos (/) ,_ ASl . lt-?f'}'-6 1 cc f\ CJ2 <(O LJ.J ACl ;9s f-C!l g~ <(Z • r-~ LJ.J<( <(CJ :I: :I: LJ.J<( u (/) X cc :I:~ LJ.J LJ.J r- LJ.J :;',! - ~ -it 1' ..... AM3 v Water ~ • Softener "'c:: Q) AM4• "0 c:: If\ 0 ~Steam To Site B via I u~ steam tunnel Tunnel --- -> Aquifer Water ----> ~
0 10 20 30 40 50 FE ET
0 10 20 METERS
EXPLANATION SITE B • AM2 Observation well and identifier To Site A via steam tunnel Value LO~ Aquifer water movement direction ~Production we ll B ----> Withdrawal step, from production well A to B BSl BCl Injection step, from production • • well B to A
Figure 3. Schematic diagram of sites A and Bat the Aquifer Thermal-Energy Storage (ATES) site. (Modified from Walton and others, 1991). Downhole gyroscopic surveys were conducted in horizontal deviations were considered during several observation wells to determine deviations of interpretation of temperature data. each well bore with respect to land surface position LONG-TERM TEST CYCLES 1 AND 2 (Hoyer and others, 199la; Miller and De lin, 1993). The bottoms of some wells deviate from their land-surface Following completion of the ATES short-term test locations by as much as 8 m horizontally (fig. 5). These cycles (Walton and others, 1991; Miller and Delin,
C7 Glacial Drift ~~~ ~~~~ Q:IQ)Q)Q) !:!~~ QJ~QJQ) "'"'"'E E E EEEE Pfatteville Formation ",P"+J".t=i ·.;::; ·+=i·.;::;·.;::; c::c::c:: c::c::c:c:: Glenwood ~ormation Cl,)Q)Q)Q) ~~~ uuuu ~~"! Ll':ILnN.- 225 MMM NNMLri
St. Peter .....1 Sandstone L.U 200
>L.U .....1 <( L.U U) 175 Prairie du s 0 Chien .....1 L.U Group r:D 0z <( L.U Jordan > 0 Sandstone r:D 125 <( U) a: St. Lawrence Formation L.U f- L.U 2 100 Franconia z Formation L.U' Cl :::::l 75 f- i= .....1 Ironton and <( Galesville 50 Sandstones
Eau Claire Formation 25
Mount Simon Sandstone
-25 PRODUCTION ACl ASl AMl AM2 AM3 AM4 WELL A SITE A
EXPLANATION
Screened interval in production well
49.7-48.8 • Altitude range of screened interval, in meters
f- 110 Temperature measurement point and altitude, in meters (refer to well AM3 for measurement altitudes)
Figure 4. Depths of screened intervals of observation wells, Thermal-Energy Storage (ATES) site. (Horizontal
C8 275 Glacial Drift 250
Platteville Formation Glenwood Formation 225
St. Peter Sandstone 200 u::l >w _J <( -182 w 175 C/') Prairie du 5 Cl _J Chien w Group co 150 ~ <( w > Jordan Cl Sandstone co <( C/') 111-4-1_11.3 r:r: St. lawrence Formation w f w :a:: Franconia z Formation 75
65 Ironton and Galesville Sandstones 4if.5:-4f6 41 I 42 36.3-35.4 Eau Claire Formation ------25
~1 L3-10.4
Mount Simon Sandstone
-25 BCl BSl PRODUCTION CMl WELL B SITE 8 SITE C
stratigraphy, and location of measurement points of the Aquifer arrangement of wells is arbitrary and not to scale.)
C9 Production well A
0 10 20 30 40 50 60 70 80 90 100 FEET
0 10 20 30 40 METERS
EXPLANATION
Position of observation well
AM4 ~ Land surface and we ll number
Model-layer 1 (St. Lawrence Formation) I Model-layer 6 (Eau Claire Formation)
Figure 5. Model grid and position of observation wells at various depths.
1994), addition of an ion-exchange water softener, and The first long-term test cycle was conducted from addition of observation well AM4, testing of the ATES November 1984 through May 1985; the second long system continued with two long-term test cycles of term test cycle from October 1986 through April 1987. heated-water injection, storage, and withdrawal. Each The duration, average rate of injection and withdrawal, cycle was planned to be approximately 180 days long; and average temperature of injection and withdrawal for the injection, storage, and withdrawal periods for each long -term test cycles 1 and 2 are shown in table 1. A third cycle each were to be approximately 60 days in duration. long-term test cycle, not described in this report, during
ClO which recovered water was sent to a heat exchanger in data are presented in graphs having temperature plotted a campus building for use, was conducted from October as a function of time and in graphs of temperature 1989 through March 1990 (Hoyer and others, 1994 ). profiles of observation wells at the start and end of each phase of the cycles. Discussion and possible Table 1. Summary of duration, average rates of injection and explanations are given for measured trends at individual withdrawal, and average temperatures of injection, storage, and observation wells and measurement points. withdrawal for long-term test cycles 1 and 2 Temperature as a Function of Time Average flow Average Phase duration rate (liters per temperature Graphs of temperature as a function of time since each (days) second) (degrees Celsius) test cycle began were used to evaluate temperature front Long-term test cycle 1 arrivals, temperature trends, maximum temperatures, 1 Injection 59.1 18.0 108.5 and transient thermal effects at specific points within the Storage 61.0 aquifer. These graphs were particularly useful at points 2 Withdrawal 58.0 18.4 74.7 where aquifer properties change between measuring Long-term test cycle 2 points. Temperatures measured at the wellhead in 3 Injection 59.3 18.3 117.7 production well A and in observation wells AM 1, AS 1, Storage 59.1 AM2, AM3, and AM4 are presented. Figures 6 through 4 Withdrawal 59.7 17.9 85.1 11 present temperatures for periods of injection, storage, 10ver a period of 76 days. and withdrawal for long-term test cycle 1; figures 12 20ver a period of 58.8 days. 3 through 17 present temperatures for injection, storage, 0ver a period of 65.0 days. and withdrawal periods for long-term test cycle 2. 40ver a period of 59.8 days. Relatively small temperature fluctuations, which Operation of the ATES system during long-term test represent intermittent failure of thermocouples due to cycles 1 and 2 was relatively trouble free. Unlike the insulation wear at kinks in the thermocouple wires or short-term test cycles, when injection was interrupted to electronic noise in the data logger, are evident in some of clean the filters after 1 or 2 days, flow was maintained for the graphs for the observation wells and should be many days at relatively constant temperatures during the ignored. An example of this type of noise is evident in long-term test cycles with few interruptions. The source the graph of the 73.1-m thermocouple between days 3 water temperature varied smoothly and the temperature and 10. Temperatures are not plotted for thermocouples of the injected water was controlled by the temperature that failed during the long-term test cycles. controller, or varied as a response to the capacity of the Temperatures for production well A were measured at heat exchanger (Hoyer and others, 1991a and 1991b). the wellhead, not within the Franconia-Ironton Injection was interrupted eight times during long-term Galesville aquifer. Therefore, temperatures for test cycle 1, and five times during long -term test cycle 2. production well A indicate when injection or withdrawal Withdrawal was interrupted once during each cycle by of heated water took place, and when injection or an electrical outage. Interruptions during the injection withdrawal was interrupted (figs. 6 and 12). When water phases resulted from malfunctioning of the ion was not flowing through the wellhead, as during periods exchange water softener, freezing of pressure shutoff of storage and during interruptions to injection or valves, and shutdowns for repairs. A detailed withdrawal, temperatures in production well A rapidly description of the operation of the long-term test cycles decreased to the air temperature at the time, below 50°C. is given in Hoyer and others (1991a and 1991b). Temperatures measured during storage periods, therefore, represent air temperatures and are not ANALYSIS OF THERMAL DATA FOR LONG representative of temperatures in the Franconia-Ironton TERM TEST CYCLES 1 AND 2 Galesville aquifer. A temperature front is hereinafter defined as the first The following sections of the report summarize and temperature increase or decrease measured at a interpret the thermal data for the long-term test cycles thermocouple, which defines the beginning of a trend of and describe the movement of heat and the changes in increasing or decreasing temperatures. Identifying the temperature in relation to the hydraulic and thermal first arrival time of a temperature front was imprecise properties of the aquifer and confining units. Thermal when the temperature changes were small and when the
Cll Cl) ::::> Cl) .....1 w u 80 Cl) w w a: (!) w Cl 70 ~ w~ a: ::::> I- <( a: w 60 a.. 2: w I-
50
Injection l temporarily stopped 40
\ ~ Injection J temporarily stopped
10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION
Figure 6. Temperatures at the wellhead in production well A
C12 Injection J temporarily started
100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION
during long-term test cycle 1, November 1984 through May 1985.
Cl3 100 St. Lawrence Formation INJECTION STORAGE 80
60
40
20 ' _j 0 140 Upper part of Franconia Formation 120
100
80
60
40
20 (I) ::> (I) 0 ~ L.LJ 100 u (I) L.LJ L.LJ 80 a: (.!) L.LJ 60 Cl z _j L.LJ- 40 a: ::> f- 20
00 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION
Figure 7. Temperatures in observation well AM1 during
C l4 I 1- STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude t- --- Temperature at 104.2 meter altitude L
r L
t- L
Ir t- --- Temperature at 93.0 meter altitude L --- Temperature at 88 .4 meter altitude r I I 1- -~ I t- I L I I I I 1- I r I I L I I I I I
I I 1- I t- : Temperature at 73.1 meter altitude L I F.======-----====:--======~ Temperature at 65.5 meter altitude r= jl -=~:::::: · ==~~~~~~~= L I I ----==- : = 1- I I t- I L I I I I
I 1- t- L
t- L I 1- t- L I 1- t- L I 1-
I 1- t- L
I t- L I 1- t- L
100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 1, November 1984 through May 1985.
CIS 100 I -I 80 ---j _j I 60 - I -; 40 _j
20 _j 0 140 I - 1 120 ---j _j 100 -; 80 _j I - I 60 ---j ~'\ / _j Pump I 40 temporarily - 1 stopped -; 20 _j I U) ::l I U) 0 -' LLJ 100 u 1 I I I I I I I I I - 1 U) Lower pa ~ of Fran con ia Formation LLJ - ---j LLJ 80 0: _j (.!) _ I LLJ 60 - Cl I z -"' 40 - _j uJ 0: ~ ::l ~ ~ t- 20 =- / ---j 80 _j I - 1 60 ---j _j 40 - 1 -; 20 _j I I 0 100 I - 1 80 ---j _j 60 _ I -; 40 _j 20 ---j _j 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 8. Temperatures in observation well AS1 during CJ6 I 1- STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude r- --- Temperature at 104.2 meter altitude L I - I r- L I 1- L I I 1- --- Temperature at 99 .1 meter altitude r-- - -- Temperature at 93.0 meter altitude L --- Temperature at 88 .4 meter altitude r- L I 1- r- L I 1- r- L I 1- I I 1- I r-- I I Temperature at 73 .1 meter altitude L I I Temperature at 65.5 meter altitude 1- 1-" L ------~ r- L I 1------Temperature at 58.2 meter altitude } r-- Ironton L ----- Temperature at 51 .5 meter altitude jeo======±==::=------...... ~------Temperature at 44.8 meter altitude } Galesville L I 1- r-- L I 1- r- L I 1- I 1- r- L r- L I 1- r- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 1, November 1984 through May 1985. C I7 St. Lawrence Formation INJECTION l STORAGE 80 I I I I 60 I - 40 - 1 120 ---1 100 - I 80 _J I - 1 60 ---1 ...J I 40 - 1 4 _j I - 1 (I) ~ 100 r---,----,----,---,----,----,----,---,----,----,----r---.----,----,---,---,----,----,---.---- I I u - 1 (I) I w I ---1 w 80 I a: I ...J (!) I I w 60 I - Cl z ------+---I 4 I _j I _I I ---1 ...J I - 1 ---1 ...J I - 1 4 80 _j -I 60 ---1 ...J I 40 - 1 4 20 _j I I oL---~--~--~--~---L ___L __ _L __ _L __ ~--~--~--__j ____L- __L_ __ il_ __ L_ __ ~--~--~--- 10or---.---,----r---,---,----,---~--~---.---.---.----.---~--.---~---r---,---,----,---- I - 1 80 ---1 ...J I 60 -1 4 _j 40~------+------~ 20 ---1 ...J 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 9. Temperatures in observation well AM2 during CI S I 1- STORAGE I WITHDRAWAL - - - Temperature at 109.7 meter altitude t- I I --- Temperature at 104.2 meter altitude L I I I I c ~ r L ~----~-~~·----I ----~--~ I I I I I t- L I 1- t- --- Temperature at 93.0 meter altitude I --- Temperature at 88.4 meter altitude 1- L I 1- t- L I I r L I 1- I 1- t- Temperature at 73 .1 meter altitude L I_ Temperature at 65.5 meter altitude r L t- L I 1- t- I 1- r L I 1- t- L I 1- r L I I I 1- t- L I 1- r L I I t- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 1, November 1984 through May 1985. Cl9 100 80 60 40 20 0 140 120 100 80 60 _j 40 20 (/) ::::> (/) 0 ...J LU 100 u I . I . I I I I I l I I (/) Lower part of Franconia Formation LU 1- LU 80 0: ~ LU 60 1- ! Cl z 1- LU• 40 0: ::::> 1- 1- 20 iol 100 80 60 40 20 0 100 80 _j 60 40 20 _j 0 0 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 10. Temperatures in observation well AM3 during C20 STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude - -- Temperature at 104.2 meter altitude L I r- --- Temperature at 93.0 meter altitude --- Temperature at 88.4 meter altitude I I r L I 1- r L I I r L I_ I 1- --- Temperature at 58.2 meter altitude } r- Ironton L --- Temperature at 51.5 meter altitude ;r ======f:::::====:::::::-Temperature at 44.8 meter altitude } Galesville L I 1- r- L I 1- r L I 1- I 1- r- L 1- r L I 1- r- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 1, November 1984 through May 1985. C21 20 I - 1 -I _I I 100 - 1 -; 80 _j I - 1 60 -I _j 40 _ I 20 _j Cl') :=J Cl') 0 -' UJ 100 u - I Cl') UJ -I UJ c: _I (.!) I UJ 60 - 1 Cl z -; UJ- 40 --"'-- I c: --"'-- - - - 1 :=J - --- f- 20 -I <( c: UJ c... 0 2 UJ 140 f- I - I 120 -I _I I 100 - 1 -; 80 _j - - I ------1 ~- -- 60 -I _j I 40 - I -; _j I - 1 0 100 I - 1 80 -I _j 60 - I -; 40 _j I - 1 20 _j 00 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 11. Temperatures in observation well AM4 during C22 I I STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude --- Temperature at 104.2 meter altitude L --- Temperature at 93.0 meter altitude Temperature at 88.4 meter altitude L Temperature at 73.1 meter altitude L I Temperature at 65.5 meter altitude I _ ------~---.,.,-- 1 I 1- --- Temperature at 58.2 meter altitude } t- Ironton L --- Temperature at 51.5 meter altitude I 1- Temperature at 44.8 meter altitude } Galesville I t- I L I I _J..--- 1- 1 -~- I t- I L I I I I I I t- I I L I I I I I I 1- t- L I 1- t- L L 100 110 140 150 160 170 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 1, November 1984 through May 1985. C23 Cl) :::1 Cl) --' UJ n)ectlon u 'I·. temporarily Cl) UJ stopped UJ a: ~ UJ Cl z w ' a: :::1 f <( a: UJ 60 c... ::2! UJ f- 50 40 30 20 10 ~ Injection ....---"? temporarily stopped o ~--~--~--~--~--~---'----L---L--~--~--~--~--~~LuL-WLL-~C---~--~~~~~ 0 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 12. Temperatures in production well A during C24 100 110 120 130 140 150 160 170 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2, October 1986 through April1987. C25 100 I St. Lawrence Formation INJECTION STORAGE - 1 80 ---j I 60 - 1 "1 40 _j I - 1 20 ---j _j I 0 140 I - 1 120 ---j _j 100 - I "1 80 _j I - 1 60 ---j _j I - 40 I "1 20 _j I (I') - 1 ::> Ci3 0 --'w 100 u I - 1 (I') w ---j w 80 c::: _j (!) w 60 0 z "1 _j w· 40 c::: ::> I- 20 ---j <( c::: _j w c... 0 ~ 140 w I I- - 1 120 ---j 100 - I "1 80 _j I -I 60 ---j _j I 40 -1 "1 20 _j I - 1 0 100 I - 1 80 _j I 60 - 1 "1 40 _j I - 1 20 -, _j 00 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 13. Temperatures in observation well AM1 during C26 STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude --- Temperature at 104.2 meter altitude r L r- L I 1- r- --- Temperature at 93.0 meter altitude L --- Temperature at 88.4 meter altitude 1- r L I 1- r- L I 1- r L I 1- I I 1- I r- I Temperature at 73.1 meter altitude L ~~~~~- -= ~~~-~:~~=~-~~~-~~~~~~~~~~~~~~~~~~Te;m;p;e;r;at;u;~~~6~5mMera~rude r i L I I I I I I r- I L I I I 1- --- Temperature at 58.2 meter altitude } t- Ironton --- Temperatu re at 51.5 meter altitude I I I=--- Temperature at 44.8 meter altitude } Galesville r -----r---- 1 L I I I 1- I I t- I L I I I_ I I I r I I L I I I I I I 1- L r L I 1- r- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2. October 1986 through April1987. C27 100 80 60 40 20 0 140 120 100 80 60 40 20 (/) :=! (/) 0 w...J 100 u (/) w w 80 a: (.!J w 60 Cl z u1 40 a: :=! f- 20 100 80 60 40 20 0 100 80 60 40 20 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 14. Temperatures in observation well AS1 during C28 STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude --- Temperature at 104.2 meter altitude L I_ r L --- Temperature at 93.0 meter altitude --- Temperature at 88 .4 meter altitude Temperature at 73.1 meter altitude t: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~T:em~pe:r:a:tu:r :eu~.5m~eraH~de ~ ~ : r- I L : --- Temperature at 58.2 meter altitude } Ironton --- Temperature at 51.5 meter altitude --- Temperature at 44.8 meter altitude } Galesville I 1- r- L I 1- r L I I I 1- r- L 1- r L I 1- r- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2, October 1986 through April1987. C29 100 80 60 40 20 0 140 120 100 Water sampling 80 60 40 20 U) ::l U) 0 -' UJ 100 u 1 I I I I I I I I - 1 U) Lower pa ~ of Fran coni a Formation t.::" Water sampling UJ - -1 UJ 80 eve nt c: _J ~ I UJ 60 - Cl I -; z ~ A.-._... _j 40 rtl'--1"-1'-- w· PC:=J"='"'= '="'=\A: c: I ::l 1- 20 - -1 Figure 15. Temperatures in observation well AM2 during C30 1- r- --- Temperature at 93.0 meter altitude L I - -- Temperature at 88.4 meter altitude L ~ I - - - 1- r- L I 1- r L I I I Temperature at 80.8 meter altitude 1- r- Temperature at 73.1 meter altitude L I ----r--_,..----~------~-----__:_T ::_:em~pe~r.::a ~tu:.:_re::__-:at 65.5 meter altitude 1- r L r- L I 1- --- Temperature at 58.2 meter altitude } Ironton L --- Temperature at 44.8 meter altitude } Galesville I 1- r L I 1- r- L I 1- r L I 1- I 1- r- L I Data lost because of equ ipm ent malfunction 1- r L I 1- r- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2, October 1986 through April1987. C3 1 100 80 60 40 20 _J a 140 Upper part of Franconia Formation 120 100 80 60 40 20 C/) :::::l C/) a _J UJ 100 u I - 1 C/) Lower part of Franconia Formation UJ _, UJ 80 a: _J ~ UJ 60 Cl z ""1 40 __J UJ- _I a: :::::l I- 20 _, 100 - I ""1 80 _I I - I 60 _, _J 40 - I ""1 20 __J I -1 a 100 I - 1 80 _, I 60 - 1 ""1 40 __J I I 20 _, _J a a 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 16. Temperatures in observation well AM3 during C32 I 1- STORAGE WITHDRAWAL --- Temperature at 109.7 meter altitude t- --- Temperature at 104.2 meter altitude L I_ I 'L 1- L I I 1- t- --- Temperature at 93 .0 meter altitude L I_ --- Temperature at 88.4 meter altitude ' I 1- t- L I I L I 1- I 1- t- Temperature at 73.1 meter altitude L Temperature at 65.5 meter altitude 'L I - : t- L I 1- t- L 1- 'L I 1- t- L I 1- 'L I 1- I 1- t- 'L I 1- t- L 100 110 130 140 150 160 170 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2, October 1986 through April1987. C33 100 80 60 40 20 0 140 120 100 80 60 . / Water sampling 1::: event _j 40 20 :: _J (/) :::l (/) 0 -' UJ 100 u I I I I I I I I I I - 1 (/) Lower part of Franconia Formation UJ 1- -j UJ 80 cr: _j (!) I UJ 60 1- - 1 Cl z 40 - l'i-- _J UJ- I I cr: I :::l f- 20 ~~ I 100 - 1 -1 80 :=J - I 60 -j _j I 40 - 1 -1 20 _J I - 1 0 100 I - 1 80 -j _j _ I 60 I -1 40 _J 20 -j _j 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 17. Temperatures in observation well AM4 during C34 I 1- STORAGE WITHDRAWAL - - - Temperature at 109.7 meter altitude t- --- Temperature at 104.2 meter altitude L I 1- r L ~ I 1- t- --- Temperature at 93.0 meter altitude L I --- Temperature at 88.4 meter altitude 1- r L I 1- t- : : l I~ 1- I 1- t- Temperature at 73.1 meter altitude L I Temperature at 65.5 meter altitude 1- :: ::...:..:. k tlL 1- --- Temperatu re at 58.2 meter altitude } t- Ironton - -- Temperature at 51 .5 meter altitude I 1- --- Temperature at 44.8 meter altitude } Galesville r I 1- t- L I 1- r L I 1- I 1- t- L I 1- r L t- L 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION long-term test cycle 2, October 1986 through April1987. C35 measured temperatures were fluctuating. The arrival of wells for both cycles typically were at the 58.2-m temperature fronts at the observation wells can be seen altitude in the upper part of the Ironton Sandstone (figs. in the graphs for the observation wells. Figure 8, for 7-11 and 13-17; table 2). The second measured arrival example, shows the arrival of a temperature front in times typically were at the 51.5-m altitude, although the observation well AS 1 less than 1 day into the injection second arrival time occurred at the 44.8-m altitude for phase of long-term test cycle 1 in the Ironton and well AS 1 (fig. 8). The rate of temperature rise was Galesville Sandstones part of the aquifer. A greatest at the 52.8-m altitude. For observation AM4 temperature front arrived in the upper part of the during the second cycle (fig. 17), the temperature Franconia Formation in observation well AS 1 after change initially was very slow; about 4 days into the about 3.5 days (fig. 8). cycle the rate of temperature change suddenly For the Ironton and Galesville Sandstones, the increased. The initial arrival may have been residual earliest arrival times for the temperature front in all heat from the previous cycle; the increase in rate may Table 2. Temperature front arrival time at measurement points in the upper part of the Franconia Formation and in the Ironton and Galesville Sandstones for long term test cycles I and 2 [m, meters; --, no data or temperature front not detected; do., ditto] Time of temperature front arrival (days since start of Well number and Altitude of measurement injection) distance from injection point (meters above sea well Stratigraphic unit level) Cycle 1 Cycle2 AMI Upper part of the Franconia Form. 99.1 3.1 1.7 7m do. 93.0 3.1 1.7 do. 88.4 4.7 1.7 Ironton and Galesville Sandstones 58.2 0.1 0.2 do. 51.5 0.1 0.8 do. 44.8 1.6 2.7 ASl Upper part of the Franconia Form. 99.1 5.0 3.5 7m do. 93.0 3.9 3.0 do. 88.4 3.9 3.0 Ironton and Galesville Sandstones 58.2 0.6 0.4 do. 51.5 1.5 1.2 do. 44.8 1.3 1.0 AM2 Upper part of the Franconia Form. 99.1 9.5 10.0 14m do. 93.0 9.5 10.0 do. 88.4 4.5 2.0 Ironton and Galesville Sandstones 58.2 3.6 1.5 do. 51.5 do. 44.8 4.8 4.0 AM3 Upper part of the Franconia Form. 99.1 12.0 10.0 14m do. 93.0 11.3 8.7 do. 88.4 Ironton and Galesville Sandstones 58.2 3.2 1.5 do. 51.5 5.0 3.2 do. 44.8 5.8 4.4 AM4 Upper part of the Franconia Form. 99.1 50.0 45.0 30m do. 93.0 40.0 35.0 do. 88.4 55.0 50.0 Ironton and Galesville Sandstones 58.2 7.0 4.5 do. 51.5 8.0 8.5 do. 44.8 12.0 12.5 C36 have been the actual arrival from the second cycle. temperature was reached at the end of the injection Multiple cycles somewhat complicate data phase. Similar observations were made for the first interpretation. cycle except at wells AS1 and AMl. For well AM4, a For the upper part of the Franconia, temperature front high temperature of between 40 and 50°C was reached arrival times were considerably slower than in the at the end of the injection phases of both test cycles. Ironton and Galesville Sandstones (figs. 7-11 and 13- Temperatures measured at several thermocouples 17; table 2). This delay is not surprising because the changed immediately at the end of injection periods and permeability of the upper part of the Franconia at the beginning of withdrawal periods. These Formation is about one-half that of the Ironton and temperature changes of generally less than 5°C, some Galesville Sandstones. The earliest arrival times for the incteases and some decreases, may be attributed to the temperature front at observation well AM 1 were at the pressure changes caused by interruptions or startups. 93.0-m and the 99.1-m altitudes during the first long The changes caused water in the piezometer tubes term test cycle (fig. 7), and at all three thermocouples adjacent to the thermocouples to move past the (88.4-m, 93.0-m, 99.1-m) during the second long-term thermocouples, moving water of a different temperature test cycle (fig. 13). The temperature front reached to the level of the thermocouple. observation well AS 1 in the upper part of the Franconia Some of the temperature-versus-time graphs for Formation first at the 93.0-m and 88.4-m, and last at the observation wells AM2 (fig. 15) and AM4 (fig. 17) 99.1-m altitudes (figs. 8 and 14). The first arrivals at show the effect of sampling the wells during the test well AM2 were at the 88.4-m altitude (figs. 9 and 15). cycles. These sampling periods are evident as sharp The first arrivals at wells AM3 (figs. 10 and 16) and vertical spikes in the graphs, such as those for the upper AM4 (figs. 11 and 17) were at the 93.0-m altitude. The part of the Franconia Formation at AM2 during the first initial arrival may have been residual heat from the 13 days of cycle 2 (fig. 15). Water samples were previous cycle; the increase in rate may have been the actual arrival from the second cycle. obtained by pumping water from the observation wells at a rate of approximately 0.06 L/s. The effect is shown The highest temperatures measured during both most frequently during the second long-term test cycle cycles in every observation well were at either the 51.5 atwellAM2(fig.15). Thepumpingcausedthesampled or 58.2 m altitudes, corresponding to the Ironton water to flow past thermocouples at all overlying Sandstone, which is the most permeable part of the temperature measurement points. When the sampled Franconia-Ironton-Galesville aquifer (Walton and water had a temperature greater (or less) than the others, 1991; Miller and Delin, 1993). The Ironton temperature detected by the thermocouples, a sudden Sandstone part of the aquifer is approximately four increase (or decrease) was measured. When sampling times as permeable as the Galesville Sandstone part of was completed, temperatures measured at the affected the aquifer, represented by the 44.8-m thermocouple. thermocouples returned to pre-sampling temperatures. Highest temperatures measured at the 44.8, 51.5, and 58.2-m thermocouples were measured during the During storage periods, when water was not added to injection phase. At all observation wells, the maximum or removed from the storage zone around production temperatures in the Ironton and Galesville Sandstones well A, temperatures in the observation wells changed were reached before the end of the injection phase, slowly. In most wells, temperature changes at the same probably due to the temperature of the injected water altitudes were generally in the same direction, either being lower toward the end of the injection phase (figs. decreasing or increasing, and of similar magnitude 6 and 12). After reaching their maximums, during both test cycles. temperatures in the Ironton and Galesville Sandstones During storage periods, heat was conducted from the at observation wells AM 1, AS 1, AM2, and AM3 upper part of the Franconia Formation both into the St. decreased similar to the trend of the injected-water Lawrence Formation and into the lower part of the temperatures. Franconia Formation. Heat was also conducted from The highest temperatures in the upper part of the the Ironton and Galesville Sandstones both into the Franconia Formation at observation wells AM 1, AS 1, lower part of the Franconia Formation and into the Eau AM2, and AM3 during the second cycle were only a few Claire Formation. Temperatures for the beginning of degrees lower than those measured in the Ironton and withdrawal periods generally were lower than the Galesville Sandstones. However, the highest temperatures at the end of the injection periods at all C37 temperature measurement points opposite the screened completed in two different units. Intra-aquifer intervals of production well A. The greatest drop in [interformational] flow during storage periods, temperature was measured at the lowest thermocouple described earlier, resulted in a slight cooling of water in in the upper part of the Franconia Formation (88.4-m the well bore as it flowed from the upper part of the altitude) and the thermocouple in the Galesville Franconia Formation into the Ironton and Galesville Sandstone (44.8-m altitude). Thermally-induced Sandstones. At the beginning of withdrawal periods, convection during storage periods may have caused the water withdrawn from the Ironton and Galesville some of the measured temperature changes. Sandstones was cooled further as it traveled up the well In addition to the heat conduction described above, bore past the unscreened lower part of the Franconia heat was also transported down the well bore of Formation. The water also lost heat through conduction production well A from the upper part of the Franconia to the well bore and casing at the beginning of Formation to the Ironton and Galesville Sandstones withdrawal periods that also caused an initial warming during storage periods. This heat transport occurred of the lower part of the Franconia Formation in the because production well A was open to both formations vicinity of the well bore. Consequently, thermal and because hydraulic heads decreased with depth, equilibrium at the wellhead, and thus the highest allowing ground water to flow down and out of the well temperatures, were not reached until12 to 24 hours into bore during storage periods. Thus, heat was transported each withdrawal period (figs. 6 and 12). from the Franconia Formation to the Ironton and Temperature Profiles Galesville Sandstones because of the convective flow of heated water through the well bore of production well Temperature profiles as a function of depth at A. individual observations wells are useful in: ( 1) Temperatures measured during withdrawal periods determining whether density-driven buoyancy flow of support the concept that transport of heat within the heated water occurs (Miller and Delin, 1994), (2) aquifer was a function of permeability; the maximum examining temperature variations in relation to decrease [cooling] of aquifer temperature occurred in hydraulic and thermal properties of the aquifer, and (3) the Ironton and Galesville Sandstones. At the start of determining possible long-term trends of vertical heat withdrawal periods, temperatures in the Ironton and loss from the aquifer. Temperature profiles are Galesville Sandstones and in the upper part of the presented for the beginning and the end of each injection Franconia Formation were somewhat lower than at the period, and for the end of each storage and recovery beginning of storage periods. Temperatures measured period for each cycle at each observation well (figs. 18 in the lower part of the Franconia Formation and in the through 22). The temperature-measurement altitudes St. Lawrence Formation and Eau Claire Formation were for each of the observation wells are shown in figure 4. somewhat higher than at the beginning of storage The temperature profiles were constructed by periods. During withdrawal periods, temperatures connecting the successive temperature-measurement initially decreased rapidly in the upper part of the values with straight lines. Where thermocouples failed, Franconia Formation, then decreased more slowly. successive operating temperature-measurement values During withdrawal periods, temperatures in the Ironton were connected with straight lines. This linear and Galesville Sandstones decreased slowly. interpolation may not accurately represent temperatures Temperatures of the withdrawal water more closely between the temperature-measurement points, resembled the temperatures in the Ironton and especially where temperatures are interpolated across a Galesville Sandstones than in the upper part of the major hydraulic or thermal boundary such as near Franconia Formation. Thus, the Ironton and Galesville confining layers or the unscreened lower part of the Sandstones contributed a majority of the water and heat Franconia Formation. Contrasts in temperatures across during withdrawal periods. The withdrawal plots (figs. major hydraulic boundaries were large (about 20 to 7-17) illustrate that, as expected, the injected heat was 40°C) following injection. The contrast in the advective not fully recovered by the end of the withdrawal heat-transport rate in the most permeable part of the periods. aquifer and the conductive heat-transport rate in the Water temperatures reached a maximum at least permeable parts of the aquifer and in the confining production well A about 12 to 24 hours after withdrawal layers was noticeable at all wells. The contrast in began (figs. 6 and 12), likely because the well was temperatures across major hydraulic boundaries is best C38 illustrated by the thermal separation, both in time and perhaps, accurately represents the potential long-term space, measured at well AM4, the most distant well effects of buoyancy flow for the Franconia-Ironton from production well A (figs. 11, 17, and 22). Although Galesville aquifer at the end of injection and storage detail is lacking for temperature variation at the periods (fig. 22). The general lack of noticeable hydraulic and thermal boundaries, the linear buoyancy flow in the test results probably was due to (1) interpolation method did not serious! y hinder use of the an insufficient density of temperature-measurement temperature profiles in describing the energy-transfer locations, and (2) vertical changes in hydraulic processes within the aquifer and confining units. properties caused by the presence of generally The shape of the temperature profiles in figures 18 continuous, thin, horizontally bedded silt, shale, and through 22 generally reflects the permeability clay stringers within the Franconia-Ironton-Galesville distribution described by Miller and Delin (1993) for aquifer (Walton and others, 1991; Miller and Delin, the Franconia-Ironton-Galesville aquifer. Highest 1994 ). These stringers could have reduced the effects of temperatures were measured in the Ironton and buoyancy flow by acting as barriers to convective flow Galesville Sandstones and in the upper part of the induced by density differences in the water. Franconia Formation, the most permeable parts of the Earlier model-sensitivity analyses (Miller and Delin, aquifer. Lowest temperatures were measured in the 1993) indicated that the decreases in temperature within lower part of the Franconia Formation, the least the upper part of the Franconia Formation near permeable part of the aquifer. Maximum temperatures production well A could be due to interformation flow in the Ironton and Galesville Sandstones and in the within the well bore of production well A. Similar upper part of the Franconia Formation at radial decreases were observed during the storage periods of distances of 7 m and 14 m from production well A, as cycles 1 and 2 (figs. 18 through 22). Temperatures in the expected, were similar to the injected water Ironton and Galesville Sandstones and the upper part of temperatures of 108.5°C (cycle 1) and 117. 7°C (cycle 2) the Franconia Formation decreased at most observation (figs. 18 through 22). The lowest temperatures were measured in the lower part of the Franconia Formation, points in all observation wells. The decrease in the St. Lawrence Formation, and in the Eau Claire temperature in the upper part of the Franconia Formation, which are confining units. By the end of the Formation at the observation wells likely resulted from withdrawal periods, temperatures in all formations were both conduction of heat to the St. Lawrence Formation within about l5°C of each other. and the lower part of the Franconia Formation and from interformation flow through production well A. The The convection of ground water created by decrease in temperature in the Ironton and Galesville differences in density between the ambient-temperature Sandstones likely resulted from conduction of heat to aquifer water and the warmer injected water is termed the Eau Claire Formation and to the lower part of the buoyancy flow (Hellstrom and others, 1979). Franconia Formation. Buoyancy flow causes thermal stratification and tilting of the thermal front (Miller and De lin, 1994 ). If The above-described interformation flow, which was buoyancy flow occurred it would be most readily confirmed by use of a flow meter, resulted from a observed near the top of an aquifer at the end of storage natural downward vertical gradient between the upper periods. part of the Franconia Formation and the Ironton and The effects of buoyancy flow were not readily Galesville Sandstones during periods of storage. This noticeable in the temperature profiles at the test facility interformation flow caused advective flow of water in (figs. 18 through 22). The effects of buoyancy flow the upper part of the Franconia Formation past the were most noticeable in the Ironton and Galesville observation wells toward production well A. Water Sandstones in observation well AM4 at the end of from the upper part of the Franconia Formation was injection and storage periods for cycle 2 (fig. 22). The cooled as it traveled down production well A past the measured buoyancy flow was small in comparison to cooler, unscreened lower part of the Franconia the buoyancy flow as described by the sensitivity Formation. This cooled water mixed with warmer water analysis for the Franconia-Ironton-Galesville aquifer in the Ironton and Galesville Sandstones and (Miller and Delin, 1993). Although the magnitude of maintained a positive advective flow outward into the buoyancy flow was small, it was likely realistic for an sandstones. This flow of water into the Ironton and operational thermal-energy storage system and, Galesville Sandstones tended to increase, or maintain, C39 115 (,) c:: "'c:: 0 "' ·- 110 ~ 10 I I _,"' .....E 0 I I ._;L.L I I (/) 105 ------+------1--- 1 I c:: I I 0 100 I I 0 · ~ I t:: E I "' 0 I I O.l.L ..... "' 95 ~ · c I I o.O I I :::> ~ I I ..t"' 90 I I _, -- --- ~ ------~ ------w 1 >w 1 _, 85 I I 80 0 -~ Cl I I co I t:: E I I f- 65 ~ \ I I I "' I I (.!)"' 45 I I I I -- -- ~------·--~ ------.:::"' c0 40 co 1 1 '+= u-"' E ::l ..... w"' l.L0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 TEMPERATURE, IN DEGREES CELSIUS CYCLE 1 CYCLE 2 EXPLANATION ---- Temperature at beginning of injection --- Temperature at end of injection --- Temperature at end of storage - - - Temperature at end of withdrawal Figure 18. Temperatures measured in observation well AM1 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2. C40 115 u c "'c 0 110 "' ·- I I ~ ~ -'"' E~ I 0 I .... ~ I (/) 105 I --- - - ~ ---- ·------+------I I 100 I I I I I I 95 I I I I I I 90 I I I I -- -- -r ------r------'w > w 85 I I -' I I EXPLANATION ---- Temperature at beginning of injection --- Temperature at end of injection - -- Temperature at end of storage - -- Temperature at end of withdrawal Figure 19. Temperatures measured in observation well AS1 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2. C4 1 115 Q) u c c 0 Q) · - 110 ~ to I ~ ro E -' ~ 0 I ,._;U.. I C/) 105 ~~~~ I ------I 100 I I ( I I I 95 I I I \ I \ \ 90 \ \ ~~~ ~~~~ ~ ~~~ ~~~~~~~~ ~ t ~ -'w > I I w 85 -' I I I co \ f- \ i= 65 I I -' I I - (I) I Q) I ro I I ~ 45 I I I I ~ ~~~ ~~~~ ~ ~~ ~ T ~ ~ ~~ ~ ~ ~ ~~ ~ ~ ~ ~~~ ~ ~ ~ ~ ~ ~ Q) c 0 40 ·=C'C ·.;::~ I - ro I / u E :J ~ ro o w u.. 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 TEMPERATURE, IN DEGREES CELSIUS CYCLE 1 CYCLE 2 EXPLANATION - --- Temperature at beginning of injection --- Temperature at end of injection --- Temperature at end of storage --- Temperature at end of withdrawal Figure 20. Temperatures measured in observation well AM2 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2. C42 115 "'u c c 0 ·- 110 "' I I ~ ~ _J"' E~ 0 I I ,._;U... I I C/l 105 --+ ------1---- 1 1 I 100 I I I I I 95 I I I I I \ I \ 90 \ Ir ------I _J w > 1 I w 85 _J I I EXPLANATION ---- Temperature at beginning of injection ----- Temperature at end of injection ---- Temperature at end of storage ----- Temperature at end of withdrawal Figure 21. Temperatures measured in observation well AM3 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2. C43 115 Q) u c c 0 Q) · - 110 ~ ~ --'"' E~ 0 ._;L.L Cl) 105 c 0 ·.;::: 100 o E t ~ "'0.. L.L0 ~ 95 ~·c"' o_O ::> g E 90 L.L --' UJ >UJ --' 85 <{ UJ Cl) UJ > 80 0 CD <{ Cl) a: 75 UJ t- UJ ~ z 70 UJ- Cl ::> t- i= 65 --' <{ 60 en Q) c 0 -otl 55 C-o "' c oCI)c "' t=~ 0 50 ~ ==> - en ~ (!)"' 45 Q) c - ~ 0 40 co ·~ u-"' E ::::J ~ UJ"' L.L0 35 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 TEMPERATURE, IN DEGREES CELSIUS CYCLE 1 CYCLE 2 EXPLANATION ---- Temperature at beginning of injection --- Temperature at end of injection --- Temperature at end of storage --- Temperature at end of withdrawal Figure 22. Temperatures measured in observation well AM4 at the beginning of injection and at the end of injection, storage, and withdrawal for long-term test cycles 1 and 2. C44 the temperatures measured at the observation wells well AM 1 being 7 m closer to production well A than completed in these formations. the bottom of well AS 1 (fig. 5). Because water temperatures were greater at well AM1, greater heat Discussion of Thermal Data conduction losses to the Eau Claire confining unit Temperatures should have been similar at the same probably occurred at that well. depths and radial distances from production well A if Time-lag heat conduction was not as apparent during the hydraulic and thermal properties were similar in all the long-term test cycles as it was in the short-term test directions. Although observation wells AM2 and AM3 cycles (Miller and Delin, 1994). The relatively long were both 14 m from production well A at land surface injection periods with few interruptions likely limited (fig. 2), the temperatures at well AM2 were noticeably time-lag heat conduction during the long-term test greater than temperatures at well AM3 (figs. 9, 10, 15, cycles. and 16). Although temperatures in the Ironton and Temperatures in the Ironton and Galesville Galesville Sandstones were similar in both wells, Sandstones generally followed the trend of the injected temperatures in the upper part of the Franconia water temperatures. Injected water temperatures were Formation were 10°C to 75°C less in well AM3 than in highest during the early part of the injection periods. well AM2. The measured ten1perature differences Therefore, maximum temperatures occurred early in the likely resulted from (1) the bottom of observation well injection periods in the Ironton and Galesville AM2 being about 16 m from production well A and the Sandstones at wells 7 and 14m from production well A. bottom of observation well AM3 being about 19m from Conversely, maximum temperatures occurred at the end production well A, and (2) anisotropy of the aquifer. of the injection periods in the upper part of the Observation well AM2 was aligned more closely with Franconia Formation at all observation wells, and in the the axis of maximum transmissivity than was Ironton and Galesville Sandstones at well AM4, located observation well AM3 (Miller, 1984). Increased 30.5 m from production well A. Results of the long ground-water flow and heat transport likely occmTed in term test cycles suggest that aquifer clogging either did association with the axis of maximum transmissivity, not occur or was insignificant. therefore resulting in higher temperatures at well AM2 than at well AM3. A significant amount of heat remained both in the aquifer and in the confining units when the long-term Although observation wells AM 1 and AS 1 were both test cycles ended. Temperatures at the end of the first 7 m from production well A at land surface (fig. 2), long-term cycle averaged about 40°C at the upper part arrival times for well AM1 were earlier than for well of the Franconia Formation and about 45°C at the AS 1. Earlier arrival times at well AM 1 were probably Ironton and Galesville Sandstones in observation wells, due to the bottom of well AS 1 being about 7 m farther similar to temperatures of water withdrawn at the end of from production well A (fig. 5). storage. Temperatures in the immediately overlying Interpretation of the temperature graphs indicates and underlying confining units were greater than those that significant heat loss occurred through conduction in the permeable part of the aquifer. A similar picture from the injection zones to the overlying St. Lawrence emerged at the end of the second long-term cycle, at confining unit (altitude 109.7 m), the underlying Eau somewhat higher temperatures. About 62 percent of the Claire confining unit (altitude 38.1 m), and the heat stored in the aquifer was recovered during each of unscreened lower part of the Franconia Formation the two long-term cycles (table 3). (altitudes 8 to 65.5 m). Heat-conduction losses were greatest to the lower part of the Franconia Formation NONISOTHERMAL MODELING OF LONG and the Eau Claire confining unit. Some of the TERM TEST CYCLES 1 AND 2 temperature increases measured in well AM1 may have been due to horizontal heat convection, because the A three-dimensional, anisotropic, nonisothermal, screened interval of production well A extended into the ground-water-flow and thermal-energy-transport top 1.5 m of the Eau Claire Formation (Miller and Delin, model was used to simulate the two long-term test 1993). Although observation wellsAM1 andAS1 were cycles. The model is similar to the three-dimensional, both 7 m from production well A at land surface, heat isothermal ground-water-flow model described by conduction losses were greater for well AM1. These Miller and Delin (1993). Miller and Voss (1986) greater heat losses probably were due to the bottom of describe discretization of the model and the sensitivity C45 2 of the lateral boundary conditions for various rates of p =pressure [M/(L-T )] (Pa), heated-water injection. q'= mass rate of flow per unit volume from sources or The finite-difference, ground-water-flow, and sinks [M/(T-L3)] (kg/m3-s), thermal-energy-transport model used in this study was t =time [T] (s), developed for waste-injection problems (lntercomp <1> =porosity [dimensionless], and Resources Development and Engineering, 1976) and V = gradient (for an axially symmetric cylindrical will be referred to in this report as the Survey Waste coordinate system, Vis Injection Program (SWIP) code. The SWIP code can be used to simulate ground-water flow and heat and solute a 1 a a -+--+ transport in a liquid-saturated porous medium; it or rae az contains both reservoir and well-bore modeling capabilities. The major model assumptions are as where r is the radial dimension). follows: The energy-balance equation describing the 1. Ground-water flow is laminar (Darcian), three transport of thermal energy in a ground-water system dimensional, and transient. (lntercomp Resources Development and Engineering, 2. Fluid density is a function of pressure, temperature, and 1976, p.3.4) concentration. 3. Fluid viscosity is a function of temperature and V • [P:H(Vp- pgVz)J + V • K • VT (2) concentration. a 4. The injected fluid is miscible with the in-place fluids. - qL- q'H = a/<1>PU + (1- <1>)(pCp)RT] 5. Aquifer properties vary with location. 6. Hydrodynamic dispersion is a function of fluid where velocity. H = enthalpy per unit mass of fluid [ElM] (J/kg), 7 .The energy equation can be described as: enthalpy in K =hydrodynamic thermal dispersion plus convection minus enthalpy out equals the change in internal energy of the system. [E/(T- L-t)] (W/m-°C), 8. Boundary conditions allow natural water movement in T =temperature [t] (°C), the aquifer and heat losses to adjacent formations. qL = heat loss across boundaries [EfT] (W), 9. Thermal equilibrium exists within the simulated area. U =internal energy per unit mass of fluid [E/M](J/kg), The basic equation describing single-phase flow in a (pCp)R =heat capacity of aquifer matrix [E!L3-T] (J/ porous medium is derived by combining the continuity m3-°C), and equation and Darcy equation for three-dimensional Cp = specific heat of aquifer matrix [ElM-T] ( J /kg-°C). flow (Intercomp Resources Development and (All other terms are previously defined.) Engineering, 1976, p. 3.4): Equations 1 and 2 are a nonlinear system of coupled (1) partial-differential equations that are solved V • [pk(Vp-pgVz)]-q' = i(q>p) ~ at numerically by discretizing the aquifer into three where dimensions (or two dimensions for radial flow) and 3 p =fluid density [M!L ] (kg/m3), developing finite-difference approximations. Finite ~=fluid viscosity [M/(L-T)] (Pa-s), difference equations (lntercomp Resources 2 k = intrinsic permeability [L ] (m2), Development and Engineering, 1976, p. 3.5) whose 2 2 g =gravitational acceleration [L/T ] (m/s ), solutions closely approximate the solutions of equations z = spatial dimension in direction of gravity [L] (m), 1 and 2 are, for the basic flow equation: Table 3. Comparison of model-computed thermal efficiencies of the aquifer and final withdrawal-water temperatures at production well A with corresponding calculated and measured values for long-term test cycles 1 and 2 Final withdrawal-water temperature, Thermal efficiency of aquifer (percent) (degrees Celsius) Long-term test-cycle ------number Calculated Model computed Measured Model computed 62 61 45.6 45.6 2 62 62 55.4 59.5 C46 u =volumetric flux (Darcy velocity) [L/T] (m/s), (3) (pCp)w =heat capacity of water [E/(L3-T)] (J/m3-°C), and for the energy equation: and Km =molecular heat conductivity of porous media [E/ 11[TwH(!1p- pgl1z)] + 11(Tci1T)- qL (4) (T-L-t)] (W/m-°C). - (q'H) = ~8[ (8) Discretization of Aquifer System The area that can be modeled around the ATES doublet-well system is limited by (1) the constraint on the finite-difference grid spacings required by the model-solution techniques, (2) the lack of alignment of and the axis of aquifer anisotropy and the axis on which the doublet wells are located, and (3) running the model for (9) large three-dimensional problems exceeded allocated where resources available at that time. Miller and Voss (1986) x, y, z =cartesian-space coordinates, describe the construction of the finite-difference grid i, j, k =grid-block indices, for the doublet-well system at the ATES site. Flow-net n = time level, t,1' analysis (Miller and Voss, 1986) makes it possible to (All other terms are previously defined.) reduce the modeled area and to simulate flow only in the Finally, the thermal-conductance term, K, in equation area around production well A, the flow region where 6 may be further defined as (Intercomp Resources energy transport is of greatest concern (figs. 23 and 24 ). Development and Engineering, 1976, p. 3.7): The equipotentials and streamlines illustrated in figures 23 and 24 are the steady-state solutions to two K = (~u)(pCP)w + K, (10) dimensional, isothermal flow in a homogeneous, where confined, infinite, anisotropic aquifer that has no a= thermal dispersivity [L] (m), regional hydraulic gradient (Miller and Voss, 1986). <1> =porosity [dimensionless], Flow outside this modeled region is represented by a C47 specified flux at model boundaries, as determined by respectively (table 5). The value of rock heat capacity flow-net analysis. represents sandstones similar to those in the Franconia The finite-difference grid for the ATES-site model Ironton-Galesville aquifer. These values were based on was oriented such that the axis of maximum data from Sommerton and others (1965), Clark (1966), transmissivity was aligned with the horizontal Helgeson and others (1978), and Robie and others coordinate direction (figs. 23 and 24). The origin of the (1978). The values were calculated by use of methods field-coordinate system shown in figures 23 and 24 was described by Martin and Dew ( 1965). arbitrarily chosen to be halfway between production The constant of propmiionality between the heat flux wells A and B. A variably-spaced grid was designed and the temperature gradient is termed thermal because of restrictions on grid size for solution accuracy conductivity. It is the quantity of heat transmitted in unit and stability inherent to the difference approximation time through a unit cross-sectional area under a unit used in the SWIP code (Intercomp Resources temperature gradient. For purposes of data analysis, Development and Engineering, 1976). Cell sizes range thermal conductivity was assumed to be isotropic in the from 0.3 mona side at production well A to a maximum aquifer system. Values of thermal conductivity (table 5) of 10.0 mona side at the periphery of the model. The were obtained from Clark (1966). grid had 6 layers with 806 cells per layer. Vertical grid Thermal diffusivity is defined as the transport of spacings were selected to correspond with the four energy by conduction due to the exchange of kinetic hydraulic zones in the Franconia-Ironton-Galesville energy between molecules. Molecular diffusion is aquifer and with the overlying and underlying confining independent of fluid velocities and is usually constant in units (table 4). The lateral boundaries of the model saturated porous media. The value of 1.56 x 106 m2/s correspond to the 4.5-m equipotential for the Ironton (table 5) used for thermal diffusivity is representative of and Galesville Sandstones (fig. 23) and for the upper sandstones in the Franconia-Ironton-Galesville aquifer part of the Franconia Formation (fig. 24 ). (Kappelmeyer and Haenel, 197 4). Thermal dispersion, Boundary and Initial Conditions resulting from fluctuations of velocity and temperature in the pore space, is similar to the more common term of Flux rates were specified at the model boundaries mechanical hydrodynamic dispersion used in solute such that the boundaries accurately represented ground mass-transport problems. Hydrodynamic dispersion is water flow and heat transport between the modeled area the name for a group of mixing mechanisms that cause and the area outside the simulated region. The correct the spreading of a solute in a flow system (Bear, 1972). boundary fluxes were determined by analysis of the Values of dispersivity are dependent on the scale of flow net for steady-state conditions (Miller and Voss, model discretization. The values shown in table 5 were 1986; Miller and Delin, 1993). The total flow crossing determined through calibration of the model. an equipotential (fig. 23 and 24) is equal to the injection rate and is thus known. In addition, an equal amount of Model Calibration flow is represented by each streamtube. Therefore, if The model was calibrated to nonisothermal quasi-steady-state flow is assumed, the distribution of conditions to ensure that the hydraulic and thermal fluxes along an equipotential is known for any injection properties selected were reasonable for simulation of rate. The locations of lateral-flux boundaries in the heat transport in the flow system. The relative model are illustrated in figures 23 and 24. More detailed importance of each property was evaluated during descriptions of the methods used to calculate the preliminary model analyses (Miller and Delin, 1993). boundary fluxes for the model are provided by Miller Model sensitivity to changes in the hydraulic properties and Voss (1986), and Miller and Delin (1993 and 1994). of hydraulic conductivity, porosity, and vertical The following is a brief description of the thermal anisotropy, plus model sensitivity to changes in the properties of the aquifer used as variables in the thermal properties of thermal conductivity of rock, heat nonisothermal model. Heat capacity is the amount of capacity of rock, and thermal dispersivity, were tested heat required to raise the temperature of a material a during preliminary model analyses (Miller and Delin, specified amount. It is the product of density and 1993). Based on results of these analyses, the model specific heat and is a measure of the ability of a material was most sensitive to changes in thermal dispersivity. 6 to store heat. Values of 1.81 x 10 and 3.89 x 103 J/m3- The longitudinal thermal dispersivity was varied from oc were used for heat capacity of rock and water, 1 to 6 m during the long-term nonisothermal model C48 Flowline Model grid 4.5-meter equ ipotential 110 I I .' I . -~ l I I IX, .' ~J-~-----\ I I l------!.1-~-- 100 \ ·- -/- I\ . - 1- .;_ ~---- ~ L_ --~ K ""' .-- \ / .. 90 .' . - v._ / - ,' " 1- ~ ~\,: Cl) ~ ~ l"'. f<, :1'. a: . ' \ - £ lf1 4.§ / LU ~ .-· k I f- ~ ,-,;: ""' .- I . - - LU 80 'p ·-. ' !"-. . ' ~ \ -A ' '~ l~ ~ r--- ~ "';--....., . - ~- !--' -....., p_ z .'~ - '\ \ I ,_! I~ f f~ ' Cl). --r-...... "'-...... -'I ·-, i- ·''"' --' 70 ' r---.: l> ~ I. A L·· / ~ --' '-- ' :;---...... LU ~ ·-, _...;.;-- ' ~ !--.' >< '\ ll A ~ .~ ' . .---- s ' '7"-, _,- < ·, L.L.. ' "" K )<. f\ Vl '::t ..:.;; P->---- ' ~ >< 0 60 ' ..-- ·, ' ' ---:-- ~ r--,.: _?'- .x ~:\ / [,.?' -= f- ' -~· -;-. z ' ~ - 0 - 0.... Cl 50 f::- ~ I-<" f- ...... !"-. -.... "- r- '.?' Jflf ..__ ~ [;...----\ -__.-->; v -0., ['X_ x :-,.:. -' 0 [," a: 40 h ~ '. ,...... :..:--- ·,_ ', )- ·-. v.: \ r'\. x "'). ~ r--..... --- : -----;k L.L.. \- ,X. LU ·,< lf I "" u < \, ....-\ ·.. ·, V )' \ 1\ '\ \-; t----. 1- ~ z ·-\ "" ...... _ ~'' v / I I ·\ \ .-- k 'x 'x '--> f- . -1 . - Cl) ~ ' r-, 'r·. ·/ .,../·r-7- '/ ..1 '\ . -- ,' ~ Cl .\ \ ~ ~ ~ ;·--I._ .J ,' _,,' - 20 ·--._v..;x / 1- .-\ . - 1·-1-1 1\ v .__ / ·- /- v ·- .. 1\ ~ ! - ""' \ 10 ~ --, v -/ / 7 . -. ""'---\ V / _____ / f-- I . - 1- .. 1-- ~\ \- ·--- /. ·-r-./1 - ---1 /-.---~ 0 A I f. I I I I \.~--;---r ·\- 1 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 DISTANCE FROM MIDPOINT OF WELLS, IN METERS EXPLANATION Ce ll in which heat transport was not simulated Streamtube ---- Model flux boundary Figure 23. Model grid and flow net for the Ironton and Galesville Sandstones near production well A for the long-term test cycles. calibration and a value of 3.33 m most accurately respectively. Model accuracy perhaps could be duplicated the measured data (table 5). Field data have improved by adjusting this long-term model following shown that transverse dispersivity usually is 0.1 to 0.3 a rigorous sensitivity analysis; however, this was not times the longitudinal dispersivity (Freeze and Cherry, deemed necessary based on the preliminary sensitivity 1979, p. 396). Therefore, the transverse thermal analyses. The model necessarily is a simplification of dispersivity was varied from 0.1 to 0.6 m during the long-term non isothermal model calibration and a value the flow system, and accuracy of the model results is of 0.33 m most accurately duplicated the measured data limited by the accuracy of the hydraulic and thermal (table 5). The final thermal and hydraulic properties input data on which the computations are based. In simulated in the model are listed in tables 5 and 6, addition, different combinations of input data could C49 Flowline Model grid 4.5-meter equipotential 110 I I .' I I I L' ~ x---~ ~~-1-~-----~---L- 1 7/" ---.!,1-~-- 100 "'-., 1- 1\ ~'-.._ 1\ 1- -~I-- EXPLANATION I Cell in which heat transport was not simulated [ Streamtube ---- Model flux boundary Figure 24. Model grid and flow net for the upper part of the Franconia Formation near production well A for the long-term test cycles. conceivably yield the same results, particularly because period of the two long-term test cycles allowed residual only two variables were adjusted during calibration. heat left in the aquifer at the storage site to be taken into The injection, storage, and withdrawal phases of the account for the second cycle. The simulated injection two long-term test cycles were simulated from the was divided into periods of injection, flow-rate change, beginning of the first long-term test cycle to the end of and injection-temperature change during each cycle the second long-term test cycle. Temperatures (table 7). Simulated flow rates during periods of measured at observation wells in the aquifer at the start withdrawal were similarly divided. of the first long-term test cycle were used as initial Calibration ofthe model to non isothermal conditions temperatures for the simulation. Modeling the entire consisted of comparing model-computed thennal cso Table 4. Layer number, thickness, and corresponding stratigraphic/hydrogeologic unit for the three-dimensional model Model Thickness layer (meters) Stratigraphic/hydrogeologic unit 7.6 St. Lawrence Formation (confining unit) 2 13.7 Upper part of the Franconia Formation (aquifer) 3 24.4 Lower part of the Franconia Formation (confining unit) 4 15.2 Ironton Sandstone (aquifer) 5 6.1 Galesville Sandstone (aquifer) 6 30.5 Eau Claire Formation (confining unit) efficiencies and withdrawal-water temperatures to measurement-point altitudes for which data were calculated and measured values (table 3). Thermal averaged to compare with the model's vertical layering. efficiency of the aquifer was computed by dividing the Thermocouples that failed completely for a cycle phase total energy injected into the aquifer system by the total were omitted from the temperature averages for energy withdrawn from the system. Calibration of the comparison with model-computed temperatures. A model also was achieved by comparing model factor that was considered when comparing model computed and average temperatures at the observation computed temperatures with measured data is the radial wells during the test cycles (figs. 25-36). The distance of measurement points from production well longitudinal and transverse dispersivities were varied A. Because of the limitations of finite-difference during nonisothermal model calibration on the basis of modeling, the actual location of measurement points relative hydraulic conductivities of the aquifer in the may not be exactly simulated in the model at the correct longitudinal and transverse directions (Miller, 1984 ). radial distance (fig. 5). As described earlier, depth The longitudinal dispersivity was varied from 1.0 to deviation surveys indicate that some of the observation 30.0 m and the transverse dispersivity was varied from wells deviate as much as 7 m horizontally for depths 0.1 to 3.0 m, similar to calibration of the model for the ranging through the model's vertical-simulation region. short-term cycles (Miller and Delin, 1994). Values of Model-computed ten1peratures for each monitoring 3.33 and 0.33 m for longitudinal and transverse dispersivity, respectively, simulated aquifer thermal point at the site were correlated with measured values efficiencies, wellhead temperatures (table 5, and figs. taking into account results of the deviation survey. 25 and 31 ), and average temperatures (figs. 26-30, and Representation of variable pumping rates and 32-36) close to measured values. injection temperatures must be considered when Model-computed temperatures were compared to comparing model-con1puted and averaged measured temperatures at each of the observation wells temperatures. Variations in inputs are illustrated in for each period of injection, storage, and withdrawal for figures 25 and 31, which show injection temperatures the two long-term test cycles. Actual temperature recorded at the wellhead and injection temperatures measurements were averaged for all measurement simulated with the model. During the long-term test points (which were operating) within each cycles, the source-water temperature varied smoothly hydrogeologic unit in an attempt to make measured and and the temperature of the injected water was controlled model-computed data comparable. Table 8 lists the by the temperature controller, or varied as a response to Table 5. Them1al properties used for simulation of the long-term test cycles 1 and 2 Thermal property Value and unit of measure Thermal conductivity, rock = 2.20 watts per meter-degree Celsius Thermal conductivity, aquifer water at 20 degrees Celsius = 0.60 watts per meter-degree Celsius 6 Thermal diffusivity = 1.56 x 10 square meter-second Heat capacity, rock = 1.81 x 106 joules per cubic meter-degree Celsius Heat capacity, aquifer water = 3.89 x 103 joules per cubic meter-degree Celsius Longitudinal dispersivity = 3.33 meters Transverse dispersivity = 0.33 meters C51 Table 6. Hydraulic properties used for simulation of the long-term test cycles Hydraulic conductivity (meters per day) Porosity Model layer Kx Ky Kz Kx:Ky (percent) 0.003 0.003 0.00003 1.00 26.8 2 2.89 1.71 .222 1.69 28.2 3 .03 .03 .0003 1.00 27.3 4 5.78 2.51 .380 2.30 25.2 5 1.45 .628 .095 2.30 25.6 6 .003 .003 .00003 1.00 31.6 the capacity of the heat exchanger (Hoyer and others, computed and averaged temperatures for observation 1991a and 1991b). well AM 1 may be related to its short distance from production well A, compared to the other observation Analysis of Simulations wells. Trends of the model-computed temperatures for A description of the differences between model observation wells AS 1 (figs. 27 and 33), AM2 (figs. 28 computed and averaged temperatures for long-term and 34), and AM3 (figs. 29 and 3S) do not agree as well cycles 1 and 2 follows. Trends in the averaged with averaged temperatures. The model did not temperatures will be discussed and related to model duplicate the rapid rise in temperatures at all results to describe thermal processes that may explain observation wells, and particularly in the Ironton and the results. As described earlier, some thermocouples Galesville Sandstones that peaked about five days into failed intermittently because of insulation wear at kinks both long-term tests. The model-computed and in the wires or electronic noise in the data logger. These averaged temperatures differ by different amounts at failures appear as small temperature fluctuations in different stages of the two cycles. For example, model figures 2S-36 and are not discussed further. computed temperatures for observation well AM4 are The model accurately predicted thermal efficiencies too high for the upper part of the Franconia Formation, of the aquifer to within about 1 percent of calculated too low for the lower part of the Franconia Formation, values for the long-term test cycles (table 3). The model and very close to measured values for the Ironton and also accurately predicted the final withdrawal-water Galesville Sandstones. The timing of the temperature temperatures to within an average of about 3 percent of changes for the Ironton and Galesville Sandstones is calculated values, or to within about 1oc for the first considerably behind the averaged temperature changes long-term test cycle and to within about soc for the (figs. 30 and 36). second long-term test cycle (table 3). For the upper part of the Franconia Formation, Model-computed and measured temperatures at model-computed temperatures during injection were production well A compare closely (figs. 2S and 31 ). generally higher than average measured temperatures However, the model-computed temperatures are except at AS 1. Initial injection temperatures at wells somewhat lower than measured temperatures AS1, AM1, and AM2 were also higher than measured throughout most of the withdrawal periods for both values. By the end of injection, the model-computed cycles (figs. 2S and 31 ). This deviation may be an temperatures were within Soc of the averaged indication that the model overestimated the down-well temperatures at all wells except AM3 for both cycles 1 flow between the two screened intervals of production and 2 and AM4 for cycle 2, which were within about well A. 10°C of the averaged values. By the end of withdrawal, The model closely matched both the trends in the model-computed temperatures in the upper part of the averaged temperature profiles and the temperatures at Franconia Formation were within about soc of the end of injection and withdrawal periods for cycles 1 averaged temperatures at all wells except AM3, which and 2. Overall, model-computed temperatures more was 30°C higher than averaged values. Model closely matched averaged values for cycle 2 than for computed temperatures at AM2 cycle 2 were higher cycle 1. The close correspondence between model- than averaged temperatures at all times. C52 Table 7. Summary of long-term test cycles 1 and 2 simulation times, durations, flow rates, and temperatures [--,not applicable] Temperature at Simulation time Duration Flow rate wellhead (days) (days) (liters per second) (degrees Celsius) LONG-TERM TEST CYCLE 1 Injection 0.0 1.6 284.0 234.0 1.6 1.2 0 2.8 6.9 282.7 235.0 9.6 3.9 294.0 234.0 13.6 5.4 296.0 234.0 18.9 .9 0 19.8 2.7 290.5 229.4 22.5 .3 0 22.8 2.7 286.6 238.3 25.5 1.4 0 26.8 9.8 286.6 233.8 36.6 7.0 0 43.6 3.4 287.8 230.5 47.0 15.7 278.0 221.5 62.7 7.3 280.0 220.0 70.0 4.7 280.0 211.3 Storage 74.7 64.0 0 Withdrawal 138.7 1.1 297.2 156.0 139.8 297.2 162.0 140.8 2 297.2 169.0 142.8 1 297.2 180.0 143.8 3 296.1 185.0 146.5 2 296.1 189.0 148.8 4.1 296 190.0 152.8 6.0 296 189.0 158.8 1.1 293.3 181.0 159.8 .8 0 170.0 160.6 3.2 293.3 175.0 163.8 5 291.8 177.0 168.8 10 289.9 167.0 178.8 5 289.9 149.0 183.8 5 288.5 140.0 188.8 5 288.3 132.0 193.8 4 286.9 125.0 197.8 0 0 120.0 LONG-TERM TEST CYCLE 2 Injection 685.8 8.3 291.7 244.6 694.1 9.5 291.7 247.5 713.7 4.1 0 717.8 13.4 291.6 241.2 731.1 8.5 291.6 243.9 739.6 7.0 285.6 241.5 746.6 3.1 285.6 237.3 Storage 749.7 58.2 0 Withdrawal 808.0 29.0 269.6 206.0 837 10 269.6 187.0 847 10 269.6 169.0 857 10.2 269.6 153.0 867.2 0 269.6 139.0 C53 130 120 110 100 90 Cl) :::::> Cl) _J L..LJ u 80 Cl) L..LJ L..LJ a: c.!J L..LJ 0 z 70 L..LJ' a: :::::> f- 50 40 30 20 10 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 25. Model-computed and measured temperatures C54 - - - Model-computed temperature --- Measured temperature at wellhead 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in production well A during long-term test cycle 1. css 80 60 40 20 0 100 Lower part of Franconia Formation 80 60 (/) ::> _j U3 40 -' _I l.U u 20 (/) l.U l.U cr: 0 ~ l.U Cl z 140 w· cr: ::> 120 f- 60 _j 40 20 0 140 I - 1 -I _j I - 1 -; _j I I -I _j I - 1 -; _j I I 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 26. Model-computed and average measured temperatures C56 STORAGE WITHDRAWAL --- Model-c omputed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes L --- Model-computed temperature --- Average temperature at 66-, L 73-, and 81 -meter altitudes L --- Model-computed temperature --- Average temperature at 52-, and 58-mete r altitudes L L I 1- --- Model-computed temperature t- --- Measured temperature at L I 45-meter altitude 1- r L I 1- t- L I I r L I I 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM1 during long-term test cycle 1. C57 STORAGE WITHDRAWAL - -- Model-computed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes L --- Model-computed temperature --- Average temperature at 66-, 73-, and 81 -meter altitudes L --- Model-computed temperature --- Average temperature at 52- , and 58-meter altitudes L L I 1- --- Model-computed temperature r- --- Measured temperature at L 45-meter altitude I - r L I 1- r- L I 1- r L I 1- 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AS1 during long-term test cycle 1. C59 --- Average temperature at 88-, 93-, and 99-meter altitudes I I --- Model-computed temperature 1- --- Average temperature at 66-, L 73-, and 81-meter altitudes L r L --- Model-computed temperatu re --- Average tempe rature at 52-, and 58-meter altitudes L I 1- --- Model -c omputed temperature 1- --- Measu re d temperature at L 45-meter altitude r L I 1- 1- L I I r L I I 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM2 during long-term test cycle 1. C61 80 60 ..J 40 4 20 _j 0 100 80 60 Cl) ::::> Cl) 40 -' UJ u 20 Cl) UJ _J UJ a: 0 (!) UJ 0 z 140 UJ- a: Ironton Sandstone .....::::> 120 60 ..J 40 4 20 _j 0 I Galesville Formation - I 120 -I ..J 100 _ I 4 80 _j I - 1 60 -I ..J I 40 - 1 4 20 _j I - 1 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 29. Model-computed and average measured temperatures C62 STORAGE WITHDRAWAL --- Model-computed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes I r L r- L L I_ I --- Model-computed temperature r- L --- Average temperature at 66-, 73-, and 81 -meter altitudes L --- Model-computed temperature --- Average temperature at 52-, and 58-meter altitudes L 1- --- Model-computed temperature r- --- Measured temperature at L I 45-meter altitude - r L I I r- L I_ I r L I I 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM3 during long-term test cycle 1. C63 140 120 _j 100 80 _j 60 40 20 _j 0 100 80 60 (I) =:J en 40 --' UJ u 20 (I) UJ UJ a: 0 C!J UJ Cl z 140 UJ- a: Ironton Sandstone =:J 1- 120 60 _j 40 20 _J 0 140 I - 1 120 -t _j I 100 - ,1 80 _J I - 1 60 -t _j I 40 -,1 20 _J I - I 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 30. Model-computed and average measured temperatures C64 STORAGE WITHDRAWAL - - - Model-computed temperature ---Average temperature at 88-, 93-, and 99-meter altitudes L --- Model-computed temperature t- ---Average temperature at 66-, L 73-, and 81-meter altitudes L t- ---Average temperature at 52-, L and 58-meter altitudes L L I 1- - - - Model-computed temperature t- --- Measured temperature at L I 45-meter altitude 1- r L I 1- r- L I I r- L I I 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM4 during long-term test cycle 1. C65 (/) :::;, Ci) ....J UJ u (/) UJ UJ a: {!J UJ Cl z UJ- a: :::;, I- <( a: UJ a... 60 ~ UJ I- 50 OL---L---~--~--J---~---L ___L __ _L __ _L __ ~-- ~--~--~~_u~u_L_~~--~--~~J_~ 0 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 31. Model-computed and measured temperatures C66 --- Model-co mputed temp erature --- Measu red temperatu re at wellhead 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in production well A during long-term test cycle 2. C67 140 I Upper part of Franconia Formation INJECTION STORAGE - I 120 ---j _j 100 - 1 "1 80 __] I - 1 60 ---j _j I 40 - 1 "1 20 __] I I 0 100 I Lower part of Franconia Formation - 1 80 ---j _j 60 I (/) :::l __] (/) 40 --' LU u 20 ---j (/) LU _j LU a: (!) 0 LU Cl z 140 LU- a: Ironton Sandstone I :::l ---j 1- 120 140 I Galesville Formation - 1 120 ---j _j 100 - I "1 80 __] I - 1 60 ---j _j 40 - I "1 20 __] _I 0 0 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 32. Model-computed and average measured temperatures C68 STORAGE WITHDRAWAL --- Model -c omputed temperature --- Aver age te mperature at 88-, 93-, and 99-meter altitudes L L --- Model-computed temperature - -- Average temperature at 66-, 73-, and 81-meter altitudes L~~~~~~~==~~ I I L I - -- Model-computed temperature --- Average temperature at 52-, I and 58-meter altitudes I r L L I 1- --- Model-co mputed temperature r --- Measured temperature at L 45-meter altitude 1- r L I 1- r L I 1- r L I 1- 100 110 130 140 150 160 170 180 200 DAYS FROM BEGINNING OF INJECTION in observation well AM1 during long-term test cycle 2. C69 80 60 ...J I 40 I -; 20 _J I I 80 60 C/) :::> C/) -' UJ u 20 C/) UJ ...J UJ c:: (.!:) UJ 0 z 140,---~--,----r---,---,---,,---,---.---,----.---,---.----.---~--,----r---,---,----,---- w· I c:: Ironton Sandstone I :::> 120 c::~ UJ 100 a.. 2 UJ I- 80 60 ...J I 40 I 20 _J 120 100 80 60 40 20 40 50 60 DAYS FROM BEGINNING OF INJECTION Figure 33. Model-computed and average measured temperatures C70 STORAGE WITHDRAWAL --- Model-computed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes I r- L L - -- Model-co mputed temperature --- Average temperature at 66-, 73 -, and 81 -meter altitudes L --- Model-computed temperature --- Average temperature at 52-, and 58-meter altitudes I 1- - -- Model-computed temperature r- --- Measured temperature at 45-meter altitude I 1- r L I_ I r- L I 1- r L I I 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AS1 during long-term test cycle 2. C7 l 140 I Upper part of Franconia Form ation INJECTION STORAGE - 1 120 __, .J 100 - 1 80 _j I - 1 60 __, .J I 40 - 1 ; 20 _j I - 1 0 100 I I I I I I I I I I Lower part of Francon ia Formation - 1 80 [- -; t:::" Wate r sampling .J I 60 - I (/) : Jl'-\A event ; :::J :.:.J (/) 40 _J L.U u 20 [- I ...., (/) L.U I .J L.U I a: 0 I I I I I I ~ I I L (.!) L.U Cl z 140 w ' I a: Ironton Sandstone I :::J __, 1- 120 <{ a: I L.U 100 a... I ~ ; L.U 80 _j 1- I I 60 __, .J I 40 I ; 20 _j I I 0 140 I Galesville Form ation - I 120 __, .J 100 I ; 80 _j I - 1 60 __, .J I 40 I ; 20 _J I - 1 0 0 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 34. Model -computed and average measured temperatures en STORAGE WITHDRAWAL --- Model-computed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes L I I- I L I I L --- Model-computed temperature --- Average temperature at 66-, L 73-, and 81-meter altitudes L I --- Model-computed temperature --- Average temperature at 52-, and 58 -meter altitudes L 1- --- Model-computed temperature t- --- Measured temperature at L 45-meter altitude 1- r L I 1- 1- L I 1- r L I I 100 110 130 140 150 160 200 DAYS FROM BEGINNING OF INJECTION in observation well AM2 during long-term test cycle 2. C73 140 120 100 80 60 40 20 0 100 80 _j 60 U) :::> _j U) 40 -' UJ u 20 --; U) UJ _j UJ a: 0 C!l UJ Cl z 140 UJ- a: Ironton Sandstone :::> f- 120 I Galesville Formation - 1 --; _j - 1 "1 _j I - 1 --; _j I - 1 "1 _j I I 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 35. Model-computed and average measured temperatures C74 STORAGE WITHDRAWAL --- Model-computed temperature --- Average temperature at 88-, 93 -, and 99-meter altitudes L --- Model-computed temperature t- --- Aver age temperature at 66 -, L 73-, and 81 -meter altitudes L t L I --- Model-computed temperature --- Average temperature at 52-, and 58-meter altitudes L 1- --- Model-computed temperature t- --- Measured temperature at L 45-meter altitude 1- r L I 1- t- L I 1- r L I 1- 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM3 during long-term test cycle 2. C75 140 120 100 80 60 40 _ I 20 _j 0 100 I - 1 80 _, _j _ I 60 I (/) ::> _j' (/) 40 ....J UJ u (/) 20 UJ _j UJ 0: 0 (.!) UJ Cl z 140 UJ- I 0: Ironton Sa ndstone I ::> _, 1- 120 <( 0: I UJ c... 100 I ~ UJ _j' 1- 80 I I 60 _, _j I 40 I , 20 _j I I 0 _,- I _j I -,I I _,- 1 _j I - 1 _j' I - 1 10 20 30 40 50 60 70 80 90 100 DAYS FROM BEGINNING OF INJECTION Figure 36. Model-computed and average measured temperatures C76 STORAGE WITHDRAWAL - - - Model-computed temperature --- Average temperature at 88-, 93-, and 99-meter altitudes L --- Model-computed temperature --- Average temperature at 66-, 73-, and 81-meter altitudes L --- Model-computed temperature --- Average temperature at 52-, and 58-meter altitudes L I 1- --- Model-computed temperature r- --- Measured temperature at L 45-meter altitude I 1- r I r- L I_ I r L I 1- 100 110 120 130 140 150 160 170 180 190 200 DAYS FROM BEGINNING OF INJECTION in observation well AM4 during long-term test cycle 2. C77 Table 8. Altitudes of measurement points where temperatures were averaged to correspond with model layers Altitude(s) of Model composited values layer Stratigraphic unit (meters) St. Lawrence Formation 110, 104 2 Upper part of Franconia Formation 99,93,88 3 Lower part of Franconia Formation 81,73,66 4 Ironton Sandstone 58,52 5 Galesville Sandstone 45 6 Eau Claire Formation 38 For the lower part of the Franconia Formation, (3) duration of injection, storage, withdrawal periods. model-computed temperatures were lower than The model should prove useful in estimating the averaged temperatures at all observation wells. The recovery temperatures of heated-water injection in the temperature differences were from less than 5 oc to as Franconia-Ironton-Galesville aquifer and is a valuable much as 30°C. This relatively poor approximation of tool in computing thermal efficiency of the aquifer. the temperatures measured in the lower part of the Results of simulating the long-term test-cycles Franconia Formation may have resulted from one or suggest that the model closely estimated temperatures at more of the following factors: (1) underestimation of the observation wells, except in the low permeability the thermal conductivity of the unit or the pipe; (2) more layers. Results of model analyses indicate that the convection transport of heat vertically within the model is accurate in predicting thermal efficiency of the observation well than is accounted for in the model; and aquifer and temperatures at production well A during (3) leakage between the upper part of the Franconia periods of withdrawal. The model is less accurate in Formation and the Ironton and Galesville Sandstones, simulating temperatures at the observation wells resulting in the transport of heat vertically within the because of the effects of aquifer anisotropy. Model observation well. accuracy in simulating temperatures at the observations The computed temperatures for the model increased wells could perhaps be improved by obtaining more slowly than the averaged temperatures, but ended additional information on anisotropy of the Franconia the injection phases at about the same temperature Ironton-Galesville aquifer and studying its effect on the (within about 10°C). Model-computed temperatures movement and direction of heat flow for the hydrologic during withdrawal typically were within 10°C of the conditions at the ATES site. averaged temperatures. Model-computed temperatures SUMMARY in the Ironton Sandstone were 20-40°C higher than averaged temperatures at well AM2. These averaged In May 1980, the University of Minnesota began a temperatures are anomalous in comparison to the project to evaluate the feasibility of storing heated water averaged temperatures at well AM3, which is at (150 degrees Celsius) in the Franconia-Ironton approximately the same radial distance from production Galesville aquifer (183 to 245 meters below land well A as well AM2. Well AM2 is on the axis of surface) and later recovering it for space heating. The minimum transmissivity (Miller, 1984). Therefore, it is University's steam-generation facilities supplied high possible that the model did not accurately simulate the temperature water for injection. This Aquifer Thermal effects of lesser transmissivity near well AM2, causing Energy Storage system had a doublet-well design in higher model-computed temperatures. For the which the injection and withdrawal wells were spaced Galesville Sandstone, model-computed and averaged approximately 250 meters apart. Water was pumped temperatures had the best match of all the simulated from one of the wells through a heat exchanger, where formations. The timing and magnitude of temperature heat was added or removed. This water was then changes were very close (less than 5°C). injected back into the aquifer through the other well. The calibrated nonisothermal model is a tool for Two long-term test cycles were conducted during evaluating aquifer thermal-energy storage. The model which high-temperature water (at 108.5 degrees Celsius can be used to evaluate the optimum: ( 1) rates of and 117.7 degrees Celsius, respectively) was injected injection and withdrawal, (2) injection temperature, and for periods of about 59 days duration. Periods of storage C78 were 61.0 and 59.1 days, and periods of withdrawal to within about 1 percent of calculated values. The were 58.0 and 59.7 days, respectively. Approximately model accurately simulated withdrawal-water equal rates of injection and withdrawal of about 18 L/s temperatures to within an average of about 3 percent of were maintained for each test cycle. Withdrawal calculated values. Graphs of model-computed temperatures averaged about 75 and 85 degrees Celsius, temperatures closely matched graphs of average respectively. measured temperatures in most cases. Results of model Temperature graphs for selected depths at individual analyses indicate that the model is accurate in observation wells indicate that the Ironton and simulating thermal efficiency of the aquifer and Galesville Sandstones received, stored, and yielded temperatures of production well A during periods of more thermal energy than the upper part of the withdrawal. The model is less accurate in simulating Franconia Formation. Vertical-profile plots and time temperatures at the observation wells because of the graphs during storage indicate that the effects of effects of aquifer anisotropy. buoyancy flow were minimal within the aquifer. The calibrated nonisothermal model is a tool for Temperature graphs indicate that the shortest arrival evaluating aquifer thermal-energy storage. The model times for temperature fronts, and the hottest can be used to evaluate the optimum: (1) rates of temperatures measured at all observation wells, were in injection and withdrawal, (2) injection temperature, and the Ironton and Galesville Sandstones. The next (3) duration of injection, storage, and withdrawal shortest arrival times, and somewhat cooler periods. The model should prove useful in estimating temperatures, were in the less permeable upper part of the recovery temperatures of heated-water injection in the Franconia Formation. The latest arrival times for the Franconia-Ironton-Galesville aquifer and is a temperature fronts were measured in the lower part of valuable tool in computing thermal efficiency of the the Franconia Formation. Because the lower part of the aquifer. Franconia Formation was not screened, heat within this REFERENCES part of the aquifer was transported by conduction. Significant heat was conducted into the lower part of the Bear, Jacob, 1972, Dynamics of fluids in porous media: Franconia Formation. However, the percentage of total New York, Elsevier, 764 p. injected heat that remained in the lower part of the Clark, S.P., 1966, Book of physical constants: Geological Franconia Formation after withdrawal was Society of America Memoir 97, 587 p. insignificant. Very little heat conduction was observed Czarnecki, J.B., 1983, Fortran computer programs to plot in the upper St. Lawrence Formation and Eau Claire and process aquifer pressure and temperature data: Formation confining layers to the aquifer. Buoyancy U.S. Geological Survey Water-Resources Investiga flow within the aquifer was minimal, as evidenced by tions Report 85-4051, 49 p. temperature profiles at individual observation wells Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Engle during periods of injection, storage, and withdrawal. wood Cliffs, N.J., Prentice-Hall, Inc., 604 p. Helgeson, H.C., Delaney, J.M., Nesbitt, H.W., and Bird, A three-dimensional, anisotropic, nonisothermal D.K., 1978, Summary and critique of the thermody ground-water-flow and thermal-energy-transport namic properties of rock forming minerals: American model was used to simulate the two long-term test Journal of Science, v. 278-A, 229 p. cycles. Calibration of the model to nonisothermal Hellstrom, G., Tsang, Chin-Fu, and Claesson, Johan, 1979, conditions consisted of comparing model-computed Heat storage in aquifers-Buoyancy flow and thermal thermal efficiencies and withdrawal-water stratification problems: Lund University (Sweden), 70 temperatures to calculated or measured values. The p. model was calibrated by comparing model-computed Hoyer, M.C., Eisenreich, S.J., Almendinger, J.E., Perlinger, J.A., Miller, R.T., Lauer, J.L., and Walton, M., 1991a, results to: (1) measured temperatures at selected University of Minnesota aquifer thermal energy storage altitudes in five observation wells, (2) measured (ATES) project report on the first long-term cycle: temperatures at the production well, and (3) calculated Pacific Northwest Laboratory, PNL-7817, UC-202, thermal efficiencies of the aquifer. The only input 137 p. properties varied during model calibration were the Hoyer, M.C., Eisenreich, S.J., Hallgren, J.P., Howe, J.T., longitudinal and transverse thermal dispersivity, which Lauer, J.L., Splettstoesser, J.P., and Walton, M., 1991b, were simulated at 3.3 and 0.33 m, respectively. The University of Minnesota aquifer thermal energy storage model accurately simulated aquifer thermal efficiencies (ATES) project report on the second long-term cycle: C79 Pacific Northwest Laboratory, PNL-7917, UC-202, ing of short-term test cycles: U.S. Geological Survey 137 p. Open File Report 93-435, 70 p. Hoyer, M.C., Hallgren, J.P., Uebel, M.H., Delin, G.N., Miller, R.T., and Voss, C.I., 1986, Design of a finite-differ Eisenreich, S.J., and Sterling, R.L., 1994, University of ence grid for a doublet-well thermal-energy storage sys Minnesota aquifer thermal energy storage (ATES) tem in an anisotropic aquifer: Ground Water, v. 24, no. project report on the third long-term cycle: Pacific 4, p. 490-496. Northwest Laboratory, PNL-9811, UC-202, 126 p. 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Walton, Matt, 1981, The University of Minnesota aquifer __ 1985, Preliminary modeling of an aquifer thermal thermal energy storage system, in Proceedings of energy storage system, in Subitzky, Seymour, eds., mechanical magnetic, and underground energy storage, Selected Papers in the Hydrologic Sciences: U.S. Geo 1981 Annual Contractors Review, August 24-26, 1981, logical Survey Water-Supply Paper 2270, p. 1-20. Washington, D.C.: Conf-810 833, U.S. Department of Miller, R.T., and Delin, G.N., 1993, Cyclic injection, stor Energy, p. 120-126. age, and withdrawal of heated water in a sandstone Walton, M., Hoyer, M.C., Eisenreich, S.J., Holm, N.L., aquifer at St. Paul, Minnesota-Field observations, pre Holm, T.R., Kanivetsky, R., Jirsa, M.A., Lee, H.C., liminary model analysis, and aquifer thermal effi Lauer, J.L., Miller, R.T., Norton, J.L., and Runke, H., ciency: U.S. Geological Survey Professional Paper 1991, The University of Minnesota aquifer thermal 1530-A, 55 p. energy storage (ATES) field test facility-System __1994, Cyclic injection, storage, and withdrawal of description, aquifer characterization, and results of heated water in a sandstone aquifer at St. Paul, Minne short-term test cycles: Pacific Northwest Laboratory, sota-Thermal data analysis and nonisothermal model- PNL-7220, UC-202, 295 p. C80 ISBN 0-607-99152-6 II 9 11111111111111111111~790607 991528 @Printed on recycled paper