Abstract
The study was carried out to investigate the dissimilar seismic amplitude responses observed in sandstone reservoirs with the same fluid saturation. This challenge now informed the analysis of different amplitude responses from the ‘Jay’ Field in order to verify the reservoirs fluids around and away from well location based on the integration of Amplitude Variation with Angle (AVA) and seismic inversions. The well log data provided were used to identify hydrocarbon bearing zones and Poisson Ratio analysis. Anomalies from the AVA analysis were investigated using the elastic impedance inversion of the near and far volumes. Crossplots of Lambda-Mu-Rho inversion were produced to relate reservoir incompressibility and rigidity modulus for lithology and fluid determination. Sand E exhibited amplitude increase with angles at well point and also away from well location (red triangle). The approximate elastic impedances of the inverted seismics are almost similar to the log estimates, an indication of good correlation. Integration of incompressibility (Lambda-Rho) and rigidity (Mu-Rho) modulus analyses reveals the presence of gas saturation in reservoir Sand G because low Lambda-Rho coincides with high Mu-Rho from both log estimates and inverted seismics. In the case of Sand D, high Lambda-Rho coincides with high Mu-Rho because it is oil saturated. This study has helped to differentiate the fluids in Sands D and G despite having similar AVA responses. The methods adopted in this work can be useful in hydrocarbon detection from seismic data in fields with similar geological setting.Keywords: Amplitude Variation with Angles; Elastic Impedance; Near and Far offsets; Full stack seismic volume
Highlights
Seismic inversion technique helps in the determination of reservoir properties away from well location (Simm, 2005)
In gas hydrates region where well information is most often sparse, Amplitude Variation with Angle (AVA) was the method used for free hydrate gas assessment as discussed by Javaherian et al, (2013)
In this study, AVA analyses and model based seismic inversion techniques were integrated to reduce the risk associated with amplitude responses from poorly compacted sandstone reservoirs
Summary
Seismic inversion technique helps in the determination of reservoir properties away from well location (Simm, 2005). The integration of high frequency log information with seismic data in model based inversion was adopted to mitigate this effect. In this study, AVA analyses and model based seismic inversion techniques were integrated to reduce the risk associated with amplitude responses from poorly compacted sandstone reservoirs.
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