Seismic Attributes Method for Prediction of Unconsolidated SandReservoirs of Heavy Oil

摘要

Heavy crude oil is known as oil that is highly viscous and of a higher density than that of conventional oil.Sand reservoirs containing heavy oil generally consist of unconsolidated sediments deposited at a shallow burial depth,with high porosity and permeability. In seismic exploration, acoustic impedance inversion is a commonly used tool inreservoir prediction. However, due to the unconsolidated characteristic of heavy oil reservoirs, the wave impedancedifference between heavy oil sandstones and mudstones becomes less apparent, thus limiting the ability of impedanceinversion to accurately characterize the reservoir. Therefore we must expand our characterization of the target heavy oilreservoirs to include correlation analysis of different seismic attributes to the unconsolidated reservoir thickness. Theresults show that there has a strong correlation between the seismic attribute value of instantaneous frequency andunconsolidated reservoir thickness, more than other seismic attributes in the target strata. Thus the instantaneousfrequency attribute can be used to predict qualitatively the lateral distribution of unconsolidated reservoirs, which in turn,indicates the vertical variation of thickness for the unconsolidated reservoirs. By using frequency attributes which aresensitive to unconsolidated sediments, coupling with additional geologic information, we can predict the distribution ofsedimentary facies accurately in the study area, which results in a more reliable prediction for the lateral and verticaldistributions of heavy oil reservoirs.