Information Last Revised: 2/17/93
TTP Reference Number: AL-2011-01
1. Technical Name of Technology: Crosswell Seismic Imaging
2. Common Name of Technology: Seismic Imaging
3. PI and Telephone No: Greg Elbring, (505) 844-4904
4. Affiliation: Sandia National Laboratories
5. Technology Category: Characterization and Monitoring Technologies - DT&E
6. Developers: VOC Non-Arid ID/ VOC Arid ID/ Sandia National Laboratories
7. Application
7.1. Where (in-situ/ex-situ): in-situ
7.2. Media: soil or rock
7.3. Targeted Contaminants: presently not used for direct contaminant identification
8. Scope of project (feasibility study, treatability, bench, pilot, field):
Development and pilot field tests.
9. Integrated Demonstration (ID) Need/Requirements:
For many remediation technologies, a good understanding of the subsurface geology must be obtained to understand contaminant transport and to best devise the proper remediation scheme. Much of this geologic input is presently derived from well log data, which may be scarce, especially in contaminated areas where drilling must be kept to a minimum. Seismic imaging provides a means to image the geology between boreholes non-intrusively. Some of this imaging can be done with surface seismics. However, placing both the source and receiver downhole results in shorter travel paths which preserves higher seismic frequencies resulting in better resolution. With an imaging method known as tomography, a two-dimensional picture of the seismic velocity between two boreholes can be created and interpreted in terms of the site geology. By comparing both compressional and shear seismic wave velocities, more information can be drawn about both rock type and fluid content. For remediation processes where the properties of the subsurface are changed, such as air sparging, steam flooding, or in-situ vitrification, comparing seismic velocity images both before and during the process can provide needed information on where the technology is being effective and to what degree changes are being implemented in the subsurface.
10. Objective
10.1. Objective of technology (i.e., This technology will destroy VOCs in groundwater.):
The objective of this project is to test existing downhole sources and receivers for applicability to environmental problems including site characterization and air sparging monitoring. This has included some minor development and modification of sources, but has concentrated on optimizing data collection techniques; improving data processing, interpretation, and imaging codes; and assessing applicability and resolution capabilities.
10.2. Baseline (baseline technology to which it is compared):
Well Logging and Surface Seismics (Well Logging)
11. Process Description:
Crosshole seismic imaging involves the fielding of a downhole source and a downhole receiver in boreholes on either side of the region to be imaged. Seismic travel times are measured between a great number (>300) source and receiver locations. These travel times are then inverted into a 2-D velocity structure through a method known as tomography. The seismic sources used generate primarily shear or primarily compressional waves, depending on the source used. Both sources are pneumatic and run on compressed gas lines from bottles on the surface. The shear wave source is a controlled vibrator while the compressional wave source is an impulse source. Comparing the velocity structures for both the compressional and shear waves provides additional information about rock properties and fluid content.
11.1. Input:
The seismic sources require compressed gas, usually either air, argon, or nitrogen, that is supplied from tanks at the surface. Electrical power for running DC motors and computer control and recording equipment is also required.
11.2. Output:
The only physical output will be the vented gas. Inert gases are used both for their physical advantages in the tool and their lack of impact on the environment. The final output of the process is a map of the 2-D velocity structure between the boreholes that can be interpreted in terms of geology and, for monitoring, a map of changes in the velocity structure as a result of the remediation process.
12. Summary of Technology Advantages (relative to the baseline: faster, better, cheaper, safer):
Seismic imaging has definite advantages over drilling and logging in that much fewer wells need to be drilled to get a continuous picture of the subsurface. This makes the method much cheaper and faster, as well as providing continuous information rather than isolated point information. Fielding seismic equipment is also much less hazardous than drilling operations. The advantages of downhole seismics compared to surface seismics is that raypaths tend to be shorter and noise levels tend to be less giving higher frequency content to the wavelet and better signal-to-noise ratios. Both these properties increase the resolution of downhole seismics over surface seismics. For monitoring changes due to remediation processes, the only other option available (EM imaging) is still being developed and comparisons cannot be made at this time.
13. Limitations of Technology (relative to the baseline: faster, better, cheaper, safer):
The seismic method will not provide the spot resolution that well logging can. Some a priori knowledge of the geology (eg. well logs at some point on the profile) is needed to interpret the velocity models in terms of geology. The expense of crosshole seismics is greater than surface seismics, although this may change as crosshole seismics become more routine.
14. Major Technical Challenges:
The major technical challenges are increasing the frequency and power output of the sources to increase resolution, improving imaging and inversion codes to handle such things as anisotropy, and decreasing the survey time through development of more rapidly fielding sources and multi-station receiver strings.
15. Technical Effectiveness:
15.1. Performance
15.1.1. Remaining Contamination: (contamination mobility reduction, volume reduction, toxicity reduction)
Summary (20 words or less): Not relevant for a monitoring technology.
Further Description (unlimited length):
15.1.2. Process Waste
15.1.2.1. Status of waste (mobility, volume, hazard, recyclability)
Summary (20 words or less): No waste other than vented air or inert gas.
Further Description (unlimited length):
15.1.2.2. Treatment (needed, available)
Summary (20 words or less): No treatment needed.
Further Description (unlimited length):
15.1.2.3. Decontamination / Decommissioning
Summary (20 words or less): Probe decontamination may be necessary only if exposed to ionizing radiation or high levels of toxic substances during fielding.
Further Description (unlimited length):
15.1.2.4. Disposal (needed, available)
Summary (20 words or less): No specific disposal requirements.
Further Description (unlimited length):
15.1.3. Practicality
15.1.3.1. Foreclose Future Options
Summary (20 words or less): No effect on future options.
Further Description (unlimited length):
15.1.3.2. Reliability
Summary (20 words or less): System is reliable and functions well with only general maintenance.
Further Description (unlimited length):
15.1.3.3. Failure Control
Summary (20 words or less): Effects of failure are restricted to hazards associated with high pressure and are easily controlled.
Further Description (unlimited length):
15.1.3.4. Ease of Use
Summary (20 words or less): Will require some training of personnel. Operation of sources require training of personnel in both source operation and operation of winches for fielding tools.
Further Description (unlimited length):
15.1.3.5. Infrastructure
Summary (20 words or less): Some additional site power may be required for winch operation and appropriately sized and cased boreholes needed.
Further Description (unlimited length):
15.1.3.6. Versatility
Summary (20 words or less): Can be of use at a wide variety of sites and in conjunction with several different remediation processes.
Further Description (unlimited length): Seismic imaging can be used at any site where
information on geology between boreholes is necessary. This is especially useful when the number of boreholes that can be drilled is restricted. It can also be used for monitoring any remediation technology that significantly changes the seismic properties of the subsurface such as air sparging, steam flooding, and water flooding.
15.1.3.7. System Compatibility
Summary (20 words or less): No compatibility problems are foreseen.
Further Description (unlimited length):
15.1.3.8. Off-the-Shelf (procurement ease)
Summary (20 words or less): Although all sources are not presently available commercially, steps are being taken to transfer the technology.
Further Description (unlimited length): Downhole seismic source technology is a new and developing field. There are a couple commercially available compressional-wave sources, such as the airgun, that are used primarily for oil and gas exploration, but can be readily modified for use in the environmental arena. No shear-wave sources are presently commercially available, though there is a poorer quality shear wave generated by the compressional wave sources.
15.1.3.9. Maintainability
Summary (20 words or less):General maintenance of sources and fielding equipment (eg. lubrication, load testing) required before fielding.
Further Description (unlimited length):
15.1.3.10. Safety Measures
Summary (20 words or less): Operational precautions for hazards from pressurized gas (150 psi) and electrical power are employed.
Further Description (unlimited length): Personnel should be trained in operating pressurized systems. Components must be periodically pressure tested for continued integrity. Electrical hazards are also possible during fielding.
15.1.4. ``Works'' (functions as intended):
Summary (20 words or less): Field demonstrations have shown good results and good correlation of imaged velocities with geology interpreted from well logs.
Further Description (unlimited length): Changes in saturation due to injected air during an air sparging experiment have also been modeled. Resolution of present system is on the order of 2 to 3 feet (approximately 1 meter).
15.2. Cost
15.2.1. Start-Up Cost
Summary (20 words or less): For necessary reusable equipment, initial costs would be about $400 K for a full system.
Further Description (unlimited length): Initial one-time expenditures for equipment needed to field the system include costs for sources and receiver, winches, tripods, PC's for source control, and seismic recording system. Estimated cost for this full system is $400K. Much of this may be available for rent or lease at a much lower cost.
15.2.2. Operations and Maintenance Cost
Summary (20 words or less): Field operations should take a three man crew 1 to 3 weeks, and 1 man a month for processing and interpretation.
Further Description (unlimited length): Field operations have been running on the order of 1 to 3 weeks, depending on survey size, for a three-man crew. This time will decrease as method moves more into the production stage. Processing and interpretation presently take on the order of one month, but will probably decrease significantly as software is streamlined.
15.2.3. Life-cycle cost
Summary (20 words or less): Life-cycle costs should not exceed start-up and operations costs except when additional wells need to be drilled.
Further Description (unlimited length):
15.3. Time
15.3.1. Years Until Available
Summary (20 words or less): Complete fielding system and interpretation software currently available, though not commercially.
Further Description (unlimited length):
15.3.2. Speed/Rate
Summary (20 words or less): Data collection takes on the order of 1 to 3 weeks, depending on survey requirements. Interpretation about 1 to 2 months.
Further Description (unlimited length): Times for both fielding and especially interpretation should decrease significantly as method develops further.
15.3.3. Years to Finish
Summary (20 words or less): Essentially finished, though work to increase source power and frequency range is continuing.
Further Description (unlimited length):
16. Environmental Safety and Health
16.1. Worker Safety
16.1.1. Exposure to Hazardous Materials/Hazards
Summary (20 words or less): No hazardous materials are associated with the equipment itself, but some exposure from site-contaminated probes or well venting is possible.
Further Description (unlimited length): The primary hazards to worker safety are associated with the pressurized lines (150 psi) and commercial bottles (2500 psi) needed for the seismic sources. Other hazards are associated with electrical power being supplied to the probes, and mechanical hazards associated with operating winches and working under overhead tripods.
16.1.2. Physical Requirements
Summary (20 words or less): Handling of probes and recording equipment (75 lbs maximum), wireline rigging, and winch operation.
Further Description (unlimited length):
16.1.3. Number of People Required
Summary (20 words or less): Three people are required for safe fielding of probes.
Further Description (unlimited length):
16.2. Public Health and Safety
16.2.1. Accidents
Summary (20 words or less): Not relevant.
Further Description (unlimited length):
16.2.2. Routine Releases
Summary (20 words or less): Not relevant.
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16.2.3. Transportation
Summary (20 words or less): Not relevant.
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16.3. Environmental Impacts
16.3.1. Ecological Impacts
Summary (20 words or less): No ecological impacts are anticipated.
Further Description (unlimited length):
16.3.2. Aesthetics
Summary (20 words or less): Some noise is associated with running of the sources, but it is very localized and not excessive.
Further Description (unlimited length):
16.3.3. Natural Resources
Summary (20 words or less): No effect on natural resources resulting from the technology itself is anticipated, but there could be effects from initial well emplacement.
Further Description (unlimited length): This effect is minimized if existing wells are used whenever possible.
16.3.4. Energy Demands
Summary (20 words or less): Standard site power is needed in sufficient quantities to operate winches, recording equipment, source motors, and PC.
Further Description (unlimited length):
17. Socio-Political Interests
17.1. Public Perception
17.1.1. Proponent Reputation
Summary (20 words or less): Sandia Laboratories has some negative recognition due to past defense work, work on nuclear waste storage, and existing waste sites.
Further Description (unlimited length): Much of this negative recognition can be avoided by transferring technology to outside company. On the positive side, Sandia also has the reputation of doing quality work.
17.1.2. Familiarity / Understandability
Summary (20 words or less): This technology is easy to understand and works with perceived benign components like compressed air and electric motors.
Further Description (unlimited length):
17.2. Tribal Rights / Future Land Use
17.2.1. Capacity for Unrestricted Use (terrestrial, aquatic)
Summary (20 words or less): Does require wells which may impact land, but process itself leaves little or no long-term impact.
Further Description (unlimited length):
17.3. Socio-Economic Interests
17.3.1. Economic Impacts
Summary (20 words or less): No significant economic impacts are anticipated.
Further Description (unlimited length):
17.3.2. Labor Force Demands
Summary (20 words or less): No significant labor force demands are anticipated.
Further Description (unlimited length):
18. Regulatory Objectives
18.1. Compatibility with Cleanup Milestones
Summary (20 words or less): Does not measure regulated properties.
Further Description (unlimited length):
18.2. Regulatory Infrastructure / Track Record
Summary (20 words or less): No impact anticipated.
Further Description (unlimited length):
18.3. Regulatory Compliance
Summary (20 words or less): Not applicable to this technology.
Further Description (unlimited length):
19. Industrial Partnerships
19.1. Company Names:
Santerra Corporation
19.2. Rationale:
Much interest in newly developed source technology has been expressed by the oil and gas industry, but little so far for environmental applications. Source technology has been transferred to an independent company in hopes of further commercialization. Commercialization of source technology for both environmental and oil and gas applications.
19.3. Contract Mechanism:
Patent Transfer
19.4. Other Potential Companies:
None at this time.
19.5. International:
None at this time.
20. Intellectual Property
20.1. Patent Ownership:
DOE and Sandia
20.2. Other Owners:
Richard Hills
20.3. Patent Number:
504317171 Advanced Downhole Periodic Seismic Generator
21. Cost Sharing:
None.
22. Background on this technology (Where did the idea come from? Who else is doing similar work? What have the results been to date? What is the most significant competitor to this technology?):
Crosshole seismic imaging developed in the oil and gas industry from imaging techniques used in the medical profession, primarily CAT scans. In the oil and gas industry, tomographic imaging is used for reservoir imaging and enhanced oil recovery monitoring. Several companies are currently working on downhole seismic sources for oil and gas exploration including Chevron Oil Field Research, Stanford University, Conoco Inc., and Bolt Technology Corp. Many of these have shown good initial results in subsurface imaging with much higher resolution than can be obtained from surface seismic methods. At the present time, no one else is applying these techniques to environmental remediation sites.
23. Reference Documents:
Elbring, G. J., 1992,``Crosshole Shear-Wave Seismic Monitoring of an In Situ Air Stripping Waste Remediation Process'', Sandia Report SAND91-2742, Sandia National Laboratories, Albuquerque, New Mexico, 55 p.
Elbring, G. J., 1991, ``Using Crosswell Seismic Imaging to Monitor In Situ Air stripping Waste Remediation Processes'', EOS, Transactions of the American Geophysical Union, 72, p.295.
Elbring, G. J., 1991, ``Crosshole Seismic Characterization and Monitoring of an In Situ Air Stripping Waste Remediation Process'', Proceedings of the Information Exchange Meeting on Characterization, Sensors, and Monitoring Technologies, Department of Energy CONF-920791, Dallas, TX.
Elbring, G. J., 1992, ``Cross-well Imaging Can Also Monitor Remediation Efforts'', Energy and Environment: A Sandia Technology Bulletin, Sandia National Laboratories, Albuquerque, NM, November, 1992.
Elbring, G. J., Hardee, H. C., and Paulsson, B. N. P., 1989, `` A Test of a Controlled Downhole Seismic Source'', Geophysics, 54, p. 1193-1198.
Hardee, H. C., 1991, ``Generating Seismic Data Downhole'', Energy and Environment: A Sandia Technology Bulletin, Sandia National Laboratories, Albuquerque, NM, March, 1991.
Hardee, H. C., Elbring, G. J., and Paulsson, B. N. P., 1987, ``Downhole Seismic Source'', Geophysics, 52, p. 729-739.