Rock physics analysis and modelling using well logs and seismic data for characterising a heterogeneous sandstone reservoir in SW of Iran

Abstract

Rock physics aims to link geological and reservoir properties to the elastic and seismic parameters. By analysing well logs and seismic data in a rock physics framework, reservoir conditions and key reservoir properties such as lithology and fluid saturations could be understood and/or predicted more precisely. In this study, we have conducted a detailed rock physics study on a heterogeneous sandstone reservoir located in south-west of Iran. First, we carried out Rock Physics Diagnostic (RPD) analysis on the data obtained from the wells based on the contact or granular-medium models and Gassmann’s fluid substitution relations. Then, by using constant-cement model that was identified as the most acceptable model in the RPD analysis, P- and S-wave velocities were predicted in several wells of the studied reservoir. Due to heterogeneous nature of the reservoir, we used various cement percentages (2–9%) for estimating seismic velocities at different subzones of the studied interval. The generated error logs show that the constant-cement model (with its optimised parameters) provides suitable approximation of velocities along the reservoir interval. In addition, by generating a Rock Physics Template (RPT) using well logs, we have evaluated the lithological and fluid saturation changes. In order to integrate the available 3D seismic data of the studied field in our rock physics study, we first performed pre-stack stochastic seismic inversion. The inversion results was then superimposed on the constructed RPT to have a first look identification of the hydrocarbon content in the whole 3D area of the reservoir framework.