Publications—Scientific Investigations Report

Prepared in cooperation with the U.S. Environmental Protection Agency,
Office of Solid Waste and Emergency Response, Office of Superfund
Remediation and Technology Innovation

Use of Borehole-Radar Methods to Monitor a Steam-Enhanced Remediation Pilot Study at a Quarry at the Former Loring Air Force Base, Maine

By Colette Grégoire, Peter K. Joesten, and John W. Lane, Jr.

 

U.S. Geological Survey Scientific Investigations Report 2006–5191

The body of the report is available in PDF Format (2,578 KB)

Abstract

Single-hole radar reflection and crosshole radar tomography surveys were used in conjunction with conventional borehole-geophysical methods to evaluate the effectiveness of borehole-radar methods for monitoring the movement of steam and heat through fractured bedrock. The U.S. Geological Survey, in cooperation with U.S. Environmental Protection Agency (USEPA), conducted surveys in an abandoned limestone quarry at the former Loring Air Force Base during a field-scale, steam-enhanced remediation (SER) pilot project conducted by the USEPA, the U.S. Air Force, and the Maine Department of Environmental Protection to study the viability of SER to remediate non-aqueous phase liquid contamination in fractured bedrock.

Numerical modeling and field experiments indicate that borehole-radar methods have the potential to monitor the presence of steam and to measure large temperature changes in the limestone matrix during SER operations. Based on modeling results, the replacement of water by steam in fractures should produce a decrease in radar reflectivity (amplitude of the reflected wave) by a factor of 10 and a change in reflection polarity. In addition, heating the limestone matrix should increase the bulk electrical conductivity and decrease the bulk dielectric permittivity. These changes result in an increase in radar attenuation and an increase in radar-wave propagation velocity, respectively.

Single-hole radar reflection and crosshole radar tomography data were collected in two boreholes using 100-megahertz antennas before the start of steam injection, about 10 days after the steam injection began, and 2 months later, near the end of the injection. Fluid temperature logs show that the temperature of the fluid in the boreholes increased by 10°C (degrees Celsius) in one borehole and 40°C in the other; maximum temperatures were measured near the bottom of the boreholes.

The results of the numerical modeling were used to interpret the borehole-radar data. Analyses of the single-hole radar reflection data showed almost no indication that steam replaced water in fractures near the boreholes because (1) no change of polarity was observed in the radar reflections; (2) variations in the measured traveltimes were unsubstantial; and (3) most of the observed decreases in reflectivity were too small to have resulted from the replacement of water by steam. Analyses of the crosshole radar tomography data also support the conclusion that steam did not replace water in the fractures around the boreholes because traveltime-difference and attenuation-difference tomograms showed only small decreases in velocity and small increases in attenuation accompanying the steam injection.

The radar data are consistent with an increase in the conductivity of the limestone as a result of heating of the limestone matrix near the boreholes. Single-hole radar reflection data collected near the end of the steam injection near the bottom of the borehole with the largest temperature increase showed substantial attenuation. Also, reflector analysis showed small decreases in the amplitudes of radar-wave reflections in data collected before injection and data collected near the end of the collection period. In the crosshole radar tomography data, decreases in velocity and small increases in attenuation also are consistent with temperature increases in the matrix.

Contents

Abstract

Introduction

Purpose and Scope

Description of Study Area

Theory of the Borehole-Radar Method

Reflection Mode

Tomography Mode

Theoretical Modeling of the Temperature Dependence of Radar-Frequency EM-Wave Propagation

Constitutive Parameters

Effect of Heating on Radar-Frequency EM Wave Velocity and Attenuation

Effect of Heating on EM-Wave Reflections from Fractures

Conclusions of the Theoretical Modeling

Collection, Processing, and Interpreted Results of Geophysical Data

Description of Monitoring Boreholes

Conventional Borehole Geophysical Logs

Fluid-Temperature Logs

Electromagnetic-Conductivity Logs

Deviation Logs

Single-Hole Radar Reflection

Data Acquisition

Data Processing and Interpretation

Analysis of the Radar Profiles

Power Correction

Spectra Analysis

Reflector Analysis

Reflection Results

Crosshole Radar Tomography

Data Acquisition

Data Processing and Interpretation

Traveltime Data

Amplitude Data

Tomography Results

Summary and Conclusions

References Cited

Figures

  1. Map showing location of the boreholes at the former Loring Air Force Base quarry site, Limestone, Maine.

  2. Diagram showing (A) transmitter and receiver antenna arrangement for single-hole radar reflection logging, and (B) typical reflection patterns from planar and point reflectors.

  3. Diagram showing configurations for collection of crosshole radar tomography data. (A) Crosshole“levelrun” data collection. (B) Tomography data collection

4-12. Graphs showing:

  4. (A) Relative dielectric permittivity , and (B) electrical conductivity of water as a function of temperature.
  5. Model results for the (A) relative dielectric permittivity, and (B) electrical conductivity of fractured limestone, and the resultant (C) velocity, and (D) attenuation of 100-megahertz radar waves as a function of temperature and conductivity (σ) in siemens per meter (S/m).
  6. Theoretical results for radar-wave traveltimes as a function of temperature and conductivity (σ), in siemens per meter (S/m) for an antenna-separation distance of 7.5 meters.
  7. Effects of the (A and B) conductivity of limestone, (C and D) conductivity of water, and (E and F) relative dielectric permittivity of water on radar-wave velocity and attenuation.
  8. Reflectivity of a 10-millimeter-thick fracture as a function of temperature, and the ratio of the reflectivity at temperature to the reflectivity at 20 degrees Celsius (°C) for formation conductivities of (A and B) 0.01 siemens per meter and (C and D) 0.03 siemens per meter.
  9. (A) Reflectivity of a 5-millimeter-thick fracture as a function of temperature, and (B) the ratio of the reflectivity at temperature to the reflectivity at 20 degrees Celsius (°C) for a formation conductivity of 0.01 siemens per meter.
  10. (A) Reflectivity of a 2-millimeter-thick fracture as a function of temperature, and (B) the ratio of the reflectivity at temperature to the reflectivity at 20 degrees Celsius (°C) for a formation conductivity of 0.01 siemens per meter.
  11. (A) Reflectivity of a 1-millimeter-thick fracture as a function of temperature, and (B) the ratio of reflectivity at temperature to the reflectivity at 20 degrees Celsius (°C) for a formation conductivity of 0.01 siemens per meter.
  12. Effect of water salinity on the radar reflection. (A) Reflectivity of a 10-millimeter water-filled fracture. (B) Reflectivity of a 10-millimeter-thick water-filled fracture. Concentration of the saline solution is 0.5845 g/L NaCl. (C) Ratio of the reflectivity with 0.5845 g/L NaCl to the reflectivity with 0.2923 g/L NaCl.

13–15. Logs showing:

  13. Temperature data collected in boreholes (A) JBW-7816 and (B) JBW-7817A during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  14. The 100-megahertz omni-directional borehole-radar reflection data collected in borehole JBW-7816 during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  15. The 100-megahertz omni-directional borehole-radar reflection data collected in borehole JBW-7817A during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.

16–29. Plots showing:

  16. Peak-to-peak amplitude of the direct radar wave of single-hole radar reflection data collected during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  17. Power term calculated for selected single-hole radar reflection data sets from boreholes JBW-7816 and JBW-7817A during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  18. Mean frequency spectra calculated for each single-hole radar reflection data set from boreholes JBW-7816 and JBW-7817A during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  19. Example of reflector analysis of single-hole radar reflection data: (A) reflector in section of radar profile, (B) mean signal in the time domain, and (C) amplitude spectrum in the frequency domain.
  20. Amplitude spectra calculated for the selected reflectors from single-hole radar reflection data collected during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  21. Ratio of the maximum amplitudes in the frequency domain of selected reflectors in single-hole radar reflection data from boreholes JBW-7816 and JBW-7817A collected during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  22. Calibrated crosshole radar levelruns. Differences in traveltimes: (A) September-August 2002 and (B) November-August 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  23. (A) Traveltimes of crosshole radar tomography data collected during August, September, and November 2002; and (B) radar-wave velocity in August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  24. Differences in crosshole radar tomography traveltimes: (A) September- August-2002 and (B) November-August 2002; at the former Loring Air Force Base quarry, Limestone, Maine.
  25. Results of the difference of the traveltime-difference tomography data: (A) September-August 2002 and (B) November-August 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  26. Peak-to-peak amplitude of the crosshole radar levelrun data: (A) unprocessed data and (B) calibrated data collected during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  27. Attenuation measurements from calibrated crosshole radar tomography data collected during August, September, and November 2002 at the former Loring Air Force Base quarry, Limestone, Maine.
  28. Attenuation differences in crosshole radar tomography data: (A) September-August 2002 and (B) November-August 2002 at the former
Loring Air Force Base quarry, Limestone, Maine.
  29. Results of the inversion of the attenuation-differences in crosshole radar tomography data: (A) September-August 2002 and (B) November-August 2002 at the former Loring Air Force Base quarry, Limestone, Maine.

Tables

  1. Power correction for selected reflectors seen in single-hole radar reflection data collected during 2002 in boreholes JBW-7816 and JBW-7817A at the former Loring Air Force Base study area, Limestone, Maine.

  2. Amplitude ratios calculated at central frequency for the selected reflectors identified in single-hole radar reflection data collected during 2002 in boreholes JBW-7816 and JBW-7817A at the former Loring Air Force Base study area, Limestone, Maine.

Suggested citation

Grégoire, Colette, Joesten, P.K., and Lane, J.W. Jr., 2007, Use of borehole-radar methods to monitor
a steam-enhanced remediation pilot study at a quarry at the former Loring Air Force Base, Maine: U.S. Geological Survey Scientific Investigations Report 2006–5191, 35 p.


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