An Integrated System for Borehole Magnetometric Resistivity and Electrical Resistivity Tomography Data Acquistion, Processing and Visualization

The U.S. DOE Office of Environmental Management (EM) was created in 1989 to manage the cleanup of large areas of environmentally contaminated sites. Since the closure of many of these sites, U.S. taxpayers have spent about $220 billion at 74 cleanup sites. However, these sites were the smallest and most manageable sites to clean. There are still over 40 sites that are deemed as enormous challenges. Among the most difficult challenges are those sites that involve fractured rock aquifers. Such sites include the Nevada Test Site, Hanford Reservation, the proposed nuclear repository at Yucca Flats, as well as other privately managed sites. These sites contain boreholes for monitoring possible contamination, but the boreholes can impact the hydrologic systems creating potential leakage pathways. Making the best use of the boreholes is critical to both cleanup and long-term stewardship of these sites. We will develop a method that combines electrical resistivity tomography (ERT) with borehole magnetometric resistivity (BMR) in order to provide detailed images around one or more boreholes at much greater resolution than surface geophysical methods and with greater depth into the formation than borehole logging techniques. Unlike cross-hole geophysical methods that require multiple closely-spaced boreholes, our method could be applied from either a single borehole or widely spaced holes. The system will be designed for rapid, inexpensive deployment. At present, there is no integrated, commercial quality system for acquisition, processing, interpretation and display of combined ERT and BMR data. One aspect of this project would be to develop an ERT and BMR string with an integrated clamp system to allow collection of ERT data in boreholes and to stabilize the magnetic sensor within the borehole. Another aspect is to develop a software interpretation package designed specifically for imaging fractured rock environments and contaminant transport flow. An inexpensive, cost-effective method of imaging that can be performed in single wells or widely spaced wells would impact the way boreholes are located, sites are characterized, and long-term monitoring. Additional savings would occur by substantially reducing the number of boreholes, improving the information from boreholes and optimizing the location of boreholes themselves. This is critical in fractured rock environments where hydrogeology is complex, the drilling costs are high and the chance of creating leakage pathways is high.