Study of pore system properties of tight gas sandstones based on analysis of the seismically derived velocity deviation log: A case study from the Perth Basin of western Australia

Abstract

The Whicher Range field of the Perth Basin includes tight sandstones of the late Permian Willespie Formation with substantial gas reserves. Reservoir properties of these sandstones, in addition to the influence of initial depositional texture, have been significantly modified by diagenesis, reflecting in fluid flow and production behavior in the field. In this study, with the target of unraveling the reservoir heterogeneity related to pore types, sandstone rock types were investigated in detail by integrating core data and velocity deviation log derived from the Wyllie equation. The results show that the variations in this parameter are intimately related to pore system properties of tight sandstone facies in the field. Estimation of velocity deviation from seismic data resulted in the identification of three main rock types (RT-1, RT-2, and RT-3) with different pore characteristics. Evaluation of the identified rock types showed that RT3, which is correlated with medium to coarse and gravely sandstones, significantly contributes to the high production reservoir zones. This rock type with isolated and traces of intergranular pore types is distributed in upper parts of the reservoir interval mainly along wells WR1 and WR4.The methodology described in this study is well working with geological, petrophysical, and seismic data. It can be employed as a prototype case study in reservoir characterization of tight sandstone reservoirs.