Integrated seismic attributes to characterize a widely distributed carbonate clastic deposit system in Khuzestan Province, SW Iran

Abstract

Integrated seismic attributes, coherency, acoustic impedance (AI), lambda–rho (λρ) and mu–rho (μρ), were used to delineate and to characterize a complex regional channel deposition system in a carbonate reservoir interval in the upper part of the Sarvak Formation. The study area incorporates three adjacent oil fields in SW Iran (Khuzestan Province) covered by three individual 3D seismic surveys having a total area of about 2800 km2. We generated a regional horizon-based coherency cube using these three seismic surveys. This revealed a carbonate clastic deposition channelling system over the entire study area. We characterized this channel deposition system in agreement with regional disconformity during the Turonian stage. To determine the petrophysical properties of the channels, we generated acoustic impedance cubes for all of the 3D seismic surveys using a convolutional-model-based inversion method. To correlate seismic attributes with reservoir well properties, we created cross-plots between acoustic impedance and total porosity values at the wells. As expected, we found a strong inverse linear correlation between the total porosity and impedance values. Since shear waves contain different rock information from those of compressional waves, we conducted an AVO attribute study on the survey in the western part of the study area. The integrated seismic attributes suggest that the porous reservoir zones correspond to the zones with lower AI, λρ and μρ values. These attributes allowed the channel distribution and lateral variations in reservoir properties to be determined. Finally, we picked the boundaries of the channels on successive time slices to create input parameters for geological models.