Final Report: Identifying Ground-Water Threats from Improperly Abandoned Boreholes

EPA Grant Number: R825549C059
Subproject: this is subproject number 059 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: Identifying Ground-Water Threats from Improperly Abandoned Boreholes
Investigators: Kubichek, Robert , Cupal, Jerry , Iverson, William P.
Institution: University of Wyoming
EPA Project Officer: Hahn, Intaek
Project Period: May 1, 1995 through May 1, 1999
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Analysis/Treatment of Contaminated Soil , Land and Waste Management


The goal of this project is to develop an acoustic test to identify such wells for possible mitigation. In this approach, a down-going acoustic pulse produces reflections at each plug boundary that are then recorded by acoustic sensors attached to the casing or steel marker post at the surface. The ultimate objective is to estimate the size and location of subsurface plugs from the recorded data.

Summary/Accomplishments (Outputs/Outcomes):

Each year many wells are plugged and abandoned throughout the United States. These include water wells, mineral exploration wells, and oil and gas production wells. Many wells penetrate one or more aquifers. The wells also pierce formations containing oil and gas reservoirs, mineral deposits such as uranium and lead, and water contaminated with salt, iron, selenium, sulfates, and radon. The well borehole provides a mechanism for communication of fluids and gasses between formations. When aquifers are involved, this poses a severe pollution threat. For example, if the borehole passes through both an aquifer and a brine-bearing
formation, the brine can invade the aquifer and compromise the quality and purity of the water. The problem escalates if the brine layer is pressurized with respect to the aquifer, causing continuous flow of brine into the fresh-water formation. Conversely, water will escape from the aquifer if its hydrostatic pressure exceeds the pressure in other porous layers. Improperly plugged wells can compromise the integrity of the aquifer layer since this natural isolation is destroyed, allowing water to come in contact with these potentially toxic materials.

We used finite-difference modeling to understand wave propagation within the plugged borehole. These experiments indicate that guided waves in fluid sections produce strong reflections at the surface that can be used to infer plug boundary locations. Computer models and field tests indicate that intrinsic attenuation through plug sections is not significant. However, spherical divergence through plug sections greatly attenuates reflections from deep plug surfaces making them undetectable in many cases. A serious problem is that even wells with simple completion and abandonment geometry can develop highly complex surface traces due to mode conversions and multiple reflections. Correct data interpretation may only be possible using finite-difference modeling based on accurate knowledge of formation velocity, densities, and structure. Unfortunately, this type of information is seldom available in practical cases.

We developed a data acquisition system, and experimented with several types of acoustic sources and sensors. A hammer source produces high-energy acoustic pulses and, when used with three-component geophone sensor elements, effectively measures reflections below 1 kHz. Piezo-electric sources and sensors implemented at 6.5 and 13 kHz provide much higher resolution, and in addition, these high-frequency pulses induce strong guided wave reflections from lower plug boundaries. Another significant advantage is the ability to electronically control the timing and spectral content of the pulses. As a result, we were able to
develop Labview-based data acquisition software to automatically record and average hundreds or even thousands of data traces per test, thus essentially eliminating effects of ambient noise.An artificial borehole constructed from 5.25 inch steel well casing provided a test bed for the equipment and a means to verify computer models. Perfect correspondence between artificial borehole tests and computer models was not obtained, however, probably because the artificial borehole was not encased in rock, unlike an actual borehole. Field tests were made on a number of plugged and unplugged wells having known plug sizes and locations. Surface plug lengths ranged from approximately 100 to 200 feet. Possible reflections from the bottom of the surface plug were observed in only 2 of the 7 plugged wells that were tested. In the other cases, no significant reflections were observed that could reasonably be interpreted as originating from known plugs. In artificial borehole tests, reflections from plug surfaces and from the end of the casing were clearly detected, but results were best for short plug lengths of less than five feet. This is consistent with computer modeling results indicating that a long surface plug strongly attenuates the reflections due to geometrical spreading of the wave front.

The biggest problem we encountered in applying the system to real-world wells was a lack of detailed information about each test site. Even when engineering drawings of the well were available and the structure appeared to be simple, many significant details remained unknown. For example, the reflection amplitude and travel time depends greatly on the (usually unknown) acoustic velocity, density, and depth of near-surface rock formations. Correct interpretation of the reflection data, including through the use of modeling software, requires accurate knowledge of these unknown parameters. Reflections from unexpected sources such as subsurface rock layers, collar joints in the casing, water or air pockets within the borehole, or surface objects such as nearby buildings and vehicles also confused the data and made interpretation extremely difficult. Finally, many wells have multiple nested casings, and in some instances the surface casing has been completely removed - both situations can result in poor acoustic coupling to the borehole and poor data quality. These problems cannot easily be resolved, at least without an additional commitment of time and money for excavation at each test site.

In conclusion, it is unlikely that an acoustic detection system can be developed for unambiguous resolution of the length or location of plugs Iying below a long surface plug. However, it does appear feasible that a system could reliably determine when a well has been improperly abandoned with a short surface plug. Since many improperly abandoned wells have only a single short surface plug, this approach could conceivably detect many of these wells and thus be a useful tool for aquifer protection. The system developed in this project is a good starting place, however tests on a variety of actual boreholes with thin surface plugs is needed for verifying and refining the approach.

Two technical papers on this research have been prepared for publication. The results of the project were presented at the Wyoming Water Conference in 1997.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 3 publications 1 publications in selected types All 1 journal articles
Other center views: All 904 publications 230 publications in selected types All 182 journal articles
Type Citation Sub Project Document Sources
Journal Article S. Choi, R. Kubichek, and J. Cupal, "Wave Propagation in Plugged Boreholes." submitted for review to the Journal of Geophysical Research. R825549C059 (Final)
not available

Supplemental Keywords:

boreholes, aquifers, oil wells, gas wells, cement plugs., RFA, Scientific Discipline, Water, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Remediation, Environmental Chemistry, Geochemistry, Chemistry, Fate & Transport, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, EPA Region, fate and transport, sediment treatment, contaminant transport, fate and transport , soil and groundwater remediation, well water, oil wells, contaminated sediment, boreholes, contaminated soil, aquifer contamination, groundwater remediation, Region 7, Region 8, chemical kinetics, contaminated groundwater, groundwater contamination, aquifers, hazardous wate, contaminated aquifers, groundwater

Relevant Websites: Exit

Progress and Final Reports:

Original Abstract
  • 1995
  • 1996
  • 1997

  • Main Center Abstract and Reports:

    R825549    HSRC (1989) - Great Plains/Rocky Mountain HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
    R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
    R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
    R825549C009 Vadose Zone Decontamination by Air Venting
    R825549C010 Thermochemical Treatment of Hazardous Wastes
    R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
    R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
    R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
    R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
    R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
    R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
    R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
    R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
    R825549C019 Development of In-situ Biodegradation Technology
    R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
    R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
    R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
    R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
    R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
    R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
    R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
    R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
    R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
    R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
    R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
    R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
    R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
    R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
    R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
    R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
    R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
    R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
    R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
    R825549C039 Remediation of Soil Contaminated with an Organic Phase
    R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
    R825549C041 Heavy Metals Removal from Contaminated Water Solutions
    R825549C042 Metals Soil Pollution and Vegetative Remediation
    R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
    R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
    R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
    R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
    R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
    R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
    R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
    R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
    R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
    R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
    R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
    R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
    R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
    R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
    R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
    R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
    R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
    R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
    R825549C061 Biofilm Barriers for Waste Containment
    R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
    R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals