Improved Characterization of Carbonate Rock Properties: A Multiphysics Integrated Approach

Abstract

Single subsurface measurement of formation properties cannot provide a complete assessment of the rock and fluid properties at reservoir conditions. The key to successful formation evaluation is through integration of data obtained with different physics, as demonstrated in this study of carbonate rock characterization. Carbonate formations are complex owing to their complicated pore structure resulting from different depositional environments and diagenesis. Derived rock petrophysical properties from multiphysics measurements of acoustics, resistivity, dielectric, and nuclear magnetic resonance (NMR) are compared with the "true" rock properties determined directly through core analyses at ambient and/or reservoir conditions. 20 core plugs were studied at both fully and partially saturated states. Results indicate that temperature is a major factor affecting the dielectric, NMR, and resistivity signals whereas pressure has less impact. Although, the selected samples were carefully chosen to represent the dominant lithofacies and rock lithologies, the NMR 1D porosity profile exhibit a heterogeneous nature for some of the plugs. After inversion of the dielectric data, the cementation factor and saturation exponent were obtained from both dielectric and resistivity experiments. In addition, the inverted shallow resistivity (Rxo) from dielectric agrees well with Rxo obtained from the resistivity measurement, demonstrating measurement consistency. Integration of the multiphysics measurements enables improved characterization of carbonate rocks. The integration procedure is based on a mathematical algorithm comparing variability in the input parameters. The added value of the current work is shown when integrating and calibrating these results with logs. It enhances the petrophysical interpretation, reduces the uncertainty in some of the petrophysical parameters, and increases understanding toward better field development strategies.