Seismic Response What causes a seismic response? 1. Changes in bulk-rock velocity or density Lithology (e.g., sandstone, shale, limestone, salt) Porosity (e.g., intrinsic, compaction, diagenesis) Mineralogy (e.g., calcite vs. dolomite, carbonaceous shales) Slide 6 Velocity and density are also affected by the type and density of the pore fluid For example, assume we have a cubic meter of rock with a porosity of 30% Let’s also assume that the density of the solid matrix is equal 2.65 g/m3 If the pore spaces of the rock were filled with salt water, the bulk density would be 2.165 g/m3 However, if the pore spaces were filled with methane, the bulk density would only be 1.856 g/m3 Fluid type and saturation (water, oil, gas) Sandstone with 30% Porosity: Pore Fluid Density Salt Water 2.164 Fresh Water 2.155 Oil 2.095 Gas 1.856 Courtesy of ExxonMobil L 13 - Seismic Attributes