Application of AVO attributes to fluid discrimination in a modern delta

The methodology described in this paper was applied in a mud-prone prograding modern deltaic area where sandy turbidites can be found in alternate sedimentary sequences together with silts and thick deepwater shales. The turbiditic deposits are characterized by channel complexes, levee/overbank systems and fan bodies.These reservoirs are normally unconsolidated and strongly affected by the presence of hydrocarbons. AVO anomalies associated with these reservoirs are related to changes in the rock compressibility and density, which are strongly affected by changes in lithology and pore fluids. Discrimination of saturant fluids was attempted by analysis of analogs generated using different hydrocarbon saturations. AVO anomalies in these synthetic seismograms were computed using fluid factor and other AVO attributes. The values found for background deviation were then used to establish threshold levels for the 3D seismic data. Prior to the computation of AVO attributes the seismic data was carefully scaled so as to keep amplitudes in the same levels as the corresponding synthetics. Using the scaled seismic data a number of AVO attributes were computed. P- and S- inversions were used to compute impedance related attributes like the ones related to the product of Lame parameters times density. The practical aspects of fluid discrimination using different attribute domains were investigated.