Noninvasive Determination of the Location and Distribution of DNAPL Using Advanced Seismic Relfection Techniques

Abstract

Recent advances in seismic reflection amplitude analysis (e.g., amplitude versus offset-AVO, bright spot mapping) technology to directly detect the presence of subsurface DNAPL (e.g., CCl4) were applied to 216-Z-9 crib, 200 West Area, DOE Hanford Site, Washington. Modeling to determine what type of anomaly might be present was performed. Model results were incorporated in the interpretation of the seismic data to determine the location of any seismic amplitude anomalies associated with the presence of high concentrations of CCl4. Seismic reflection profiles were collected and analyzed for the presence of DNAPL. Structure contour maps of the contact between the Hanford fine unit and the Plio/Pleistocene unit and between the Plio/Pleistocene unit and the caliche layer were interpreted to determine potential DNAPL flow direction. Models indicate that the contact between the Plio/Pleistocene unit and the caliche should have a positive reflection coefficient. When high concentrations of CCl4 are present, the reflection coefficient of this interface displays a noticeable positive increase in the seismic amplitude (i.e., bright spot). Amplitude data contoured on the Plio/Pleistocene-caliche boundary display high values indicating the presence of DNAPL to the north and east of the crib area. The seismic data agree well with the well control in areas of high concentrations of CCl4.

Seismic stratigraphic subdivision of the Triassic succession in the Central North Sea; integrating seismic reflection and well data

“…The presence of calcrete in sedimentary rocks gives rise to higher acoustic impedance than in similar rocks without calcrete (Temples et al 2001). Thus, the upper amplitude anomaly of unit tsu-2 is inferred to reflect an overall lower content in calcrete cementation in this unit than in the overlying tsu-3 unit.…”

Integrated geophysical and geological investigation of a heterogeneous fluvial aquifer in Columbus Mississippi

“…However, refraction data generally lack the ability to constrain meter-scale stratigraphic variability in the aquifer. Seismic reflection data provide much higher horizontal resolution than refraction data, and amplitude analysis of reflection data holds great promise for identification of dense liquid contaminants (Temples et al, 2001). For these reasons, its use is growing in hydrogeophysical studies (e.g., Bachrach and Nur, 1998;Shtivelman and Goldman, 2000;Bachrach and Mukerji, 2001).…”

A survey of the geophysical properties of chlorinated DNAPLs

“…Chlorinated solvents, including trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride, are the most important sub-class of DNAPLs due to their wide-spread use in the electronics, chemical, dry-cleaning, and metal fabrication industries. A variety of geophysical techniques have been proposed for the detection of DNAPLs in the shallow subsurface (Romig, 2000) including groundpenetrating radar (GPR) (Olhoeft, 1992; Brewster and Annan, 1994;Sneddon et al, 2000), seismic techniques (Temples et al, 2001), nuclear magnetic resonance (NMR) ( Bryar and Knight, 2003), resistivity methods (Newmark et al, 1997), induced polarization ( Grimm and Olhoeft, 2004;Briggs et al, 2004), and spontaneous potential measurements . However, most of these methods lack the spatial resolution and/ or sensitivity for the direct characterization of small DNAPL lenses or pools.…”