Seismic Reflection Attribute Analysis and Inversion Techniques to Map Stratigraphic Interfaces and Thin Beds

摘要

We demonstrate, using data from two different sites, that seismic attribute analysis andrnconstrained seismic inversion applied to high-resolution seismic reflection data canrnincrease the resolution of the data to delineate shallow (< 35 m depth) thin (< 1 m) bedsrnand stratigraphic interfaces that might not otherwise be identified. During siterncharacterization, delineating these features is important because contaminants such asrnDNAPLs tend to accumulate at stratigraphic interfaces (buried channels) and in finegrainedrnbeds. The traditional method for characterizing these features is drillingrnnumerous boreholes and correlating the interfaces between holes. Noninvasive shallowrnhigh-resolution seismic reflection surveys can provide a near continuous record ofrnvertical and spatial geologic/lithologic changes between boreholes. Unfortunately thernseismic section is a smoothed version of the subsurface representing differences inrnreflectivity at a resolution far lower than provided by geophysical logs. Seismic attributernanalysis and constrained seismic inversion techniques use the properties of borehole datarn(fine resolution) and seismic data (coarser resolution) in combination to produce arnseismic properties model with a vertical resolution close to that found in borehole logs,rnbut with added horizontal dimension.rnAt United States Department of Energy's Hanford Site in Washington seismic impedancernstacks were used to map thin silt layers, not evident on the standard amplitude stacks,rnwhere carbon tetrachloride was accumulating. Also buried channels and otherrnstratigraphic features that are potential contaminant pathways at this site were betterrndefined. At Marine Corps Air Station Beaufort, South Carolina seismic impedance stacksrnwere used to map the continuity of a clay confining unit.