Direct estimation of petrophysical properties from elastic parameter: A Case Study on the Batu Raja Formation

Abstract

Rock physics analysis is a method to characterize petrophysical properties of rocks based on their elastic behaviour. However, this approach requires complete information on mineral composition of the matrix, pore-filling fluids, and in-situ conditions of the reservoir. Recently, a new approach was introduced to model the rock physics of clastic sediments using only acoustic impedance (AI) and the ratio between P- and S- wave velocity (Vp/Vs ratio) for predicting fluid saturation and porosity without requiring detailed Voigt-Reuss-Hill and/or Hashin-Shtrikman bounds and Gassmann fluid substitution. In this study, we combine AI and Vp/Vs ratio to form pseudo elastic impedance attributes that based on attribute rotation scheme. We apply the approach to carbonate sediments in the Batu Raja formation. We combined AI and Vp/Vs ratio to produce SCPEI (Simple Curved Pseudo Elastic Impedance) and SPEIL (Simple Pseudo Elastic Impedance for Lithology) attribute to obtain better estimation of water saturation and porosity, respectively. This new approach provides a way of estimating the two main petrophysical properties, namely porosity and water saturation, from elastic properties commonly derived from seismic inversion.