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Borehole Induction Logging For The Dynamic Underground Stripping Project Llnl Gasoline Spill Site
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 7th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, Mar 1994, cp-208-00019
Abstract
Borehole induction logs were acquired for the purpose of characterizing<br>subsurface physical properties and monitoring steam clean up activities at the<br>Lawrence Livermore National Laboratory. This work was part of the Dynamic<br>Underground Stripping Project’s demonstrated clean up of a gasoline spill. The<br>site is composed of unconsolidated clays, sands and gravels which contain<br>gasoline both above and below the water table. Induction logs were used to<br>characterize lithology, to provide “ground truth’ resistivity values for electrical<br>resistance tomography (ERT), and to monitor the movement of an underground<br>steam plume used to heat the soil and drive volatile organic compounds (VOCs)<br>to the extraction wells.<br>Induction logs collected before steaming show close correlation with<br>lithology and are useful for identifying the more permeable zones. The sands and<br>gravels are readily identified by a relatively high resistivity as compared to the<br>silts and clays. During the steam injection phase, subsurface temperatures were<br>monitored and induction logs were obtained periodically. The resistivity<br>decreases throughout the heated zone. Subsurface resistivities typically dropped<br>by a factor of two or more as the subsurface temperature increased to more than<br>1OOoC. Contour plots of the induction data from several of the monitoring wells<br>also indicate regions and depths of low resistivities corresponding with the<br>steam saturated gravels. In the fine-grained silts and clays, the decrease in<br>resistivity is primarily a result of temperature effects; in the coarser-grained<br>sediments, both the fluid saturation and chemistry change as well as the<br>temperature, resulting in lower resistivities (Newmark and Wilt, 1992).