HR: 1330h
AN: H22C-0948    [PDF]
TI: Comparison of Laboratory Data and Theoretical Predications of P-wave Transmission Through NAPL/Water Mixtures in Unconsolidated Porous Media
AU: Geller, J T
EM: jtgeller@lbl.gov
AF: Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd. MS 90-1116, Berkeley, CA 94720 United States
AU: * Ajo-Franklin, J B
EM: jfrank@pangea.stanford.edu
AF: Stanford University, Mitchell Bldg, Rm. 360, Stanford, CA 94305 United States
AB: Laboratory measurements have shown that the presence of NAPL contaminants in unconsolidated porous media cause a reduction in P-wave velocity (Vp) and increased attenuation compared to water-saturated conditions. These results motivated our current project to test the ability of high-frequency seismic crosswell tomography to monitor remediation-induced changes in DNAPL distribution. As part of this project, we evaluate several constitutive models relating media properties and NAPL saturation to P-wave transmission characteristics. An appropriate relationship is useful for both estimating NAPL detectability limits and quantitatively interpreting seismic tomography results from the field. Gassman_s fluid substitution relationships under-predict the magnitude of Vp changes measured in synthetic sand packs and aquifer core samples having variable NAPL saturations. The specific conditions of the shallow subsurface such as low effective stress, high porosity (30-40%), and irregular grain shapes may contribute to the discrepancy. Intrinsic fluid phenomena such as adhesion tension or pore-scale fluid distribution may also play a role. We present new measurements of Vp and seismic attenuation in partially NAPL saturated glass-bead packs. These results provide a controlled model for comparison to our previous work on natural aquifer samples and grain geometry closer to that assumed by traditional contact models. We also consider the applicability of the Biot, Biot-squirt, and scattering models to P-wave velocity and attenuation prediction for the NAPL saturated samples.
DE: 1831 Groundwater quality
DE: 5102 Acoustic properties
DE: 5144 Wave attenuation
DE: 5194 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting