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Environmental Technology Listing
Title of Listing:
Electromagnetic Offset Log (EOL)
Category:
Characterization Technologies
Subcategory:
 *Water, Soil, All Listings
Media:
Soil, Water
Contaminants:
Resistivity
Web Site:
Email:
WMI@NETCOM.COM
Technology Description:

Waste Microbes, Inc. has developed the Electromagnetic Offset Log to evaluate hydrocarbon and other contamination below surface to provide a 3-D isometric view of the contamination plume in color. This is useful for defining a groundwater migration offsite, as well as hydrocarbons in the vadose zone or dense hydrocarbons that are subsurface to the groundwater. This method will assist in designing a cost effective treatment method.

          The EOL technique is a borehole version of a common induction method for measuring resistivity. The basics of induction techniques are to use a coil of wire as a transmitter coil, at a selected frequency. The receiver coil detects a signal which is affected by the resistivity of the earth. If the distance between the receiver and transmitter is varied, different parts of the earth effect the receiver signal. The signals obtained from a series of these measurements, made at different distances and locations, can be used to determine the resistivity variations within the earth. Induction methods are a popular way of measuring resistivity because they do not require a borehole to be drilled at each measurement point as is required for direct measurements.

          Surface measurements of resistivity using induction methods are made with both the transmitter and the receiver coil on the surface. The EOL technique is basically the same idea with receiver coil down the borehole. However, the geometry of phase focusing EOL measurements offers a significant improvement in the vertical and horizontal resolving power as compared to surface measurements.

          The phase sensitive coil used in the EOL is secured in a logging probe 1.5 inches in diameter. The electromagnetic source coil used is square shaped, approximately 6 feet on a side. A 263 Hertz, signal is easily separated out of 60-cycle power line noise and the 120-cycle cathodic-protection noise used on pipelines. The transmitter coil is placed horizontally on the surface. The receiver coils have the same orientation in the borehole.
Performance Status/
Limitations:

Performance Status:

          Waste Microbes, Inc. has been using the Electromagnetic offset Logging (EOL) for the past six (6) years on a whole of range sites. On several of the sites additional testing was done for confirmation.

          Limitations:

          There are just a few limitations for this technology. The most common is where the contamination is deeper than the monitoring well (MW). In this case we would not be able to contemplate the 3-D color isometric of contaminate below the MW depth. Another limitation is when the well is metal cased. There are other disturbances in the environment, but they can be filtered out.

          Sometimes when our coil is adjacent a large metal object, the interference results in a distorted signal. Troubleshooting this problem would be to move the coil a few feet and relog that point.
Topics
Electromagnetic Fields (EMF), Groundwater Characterization, Technologies, Characterization
Additional Topics/Tags/Keywords
Groundwater, Plume, Logging, 3-D

Organization:
WMI International, Inc.
Address:
4901 Milwee
Suite 109
Phone:
DescriptionNumber
City:
Houston
1.
Primary (713) 956-4001
State/Province/Territory:
TX
2.
Zip/Postal Code:
77092
3.
Country:
United States
4.
Fax:(713) 956-7305
Branch Locations: