Rock physics application for predicting thermal maturation of organic-rich carbonates

High-resolution reservoir models are typically based on the inversion of seismic data to calculate the seismic layer properties such as P- and S-wave impedances, density, Poisson’s ratio, Vp/Vs ratio, etc. The challenge is to establish strong and reliable geostatistical relations between these seismic layer properties and petrophysical/geomechanical properties using both well logs and laboratory measurements. Establishing these rock physics (RP) relations and appropriate models can be valuable in delineating the spatial distribution of key rock properties in a petroleum system. In this study, we develop RP models, based primarily on the modified lower Hashin-Shtrikman bounds (MLHS) and Gassmann's fluid substitution equations, to predict the porosity, water saturation, and thermal maturity of organic-rich carbonates from the Golan basin in northern Israel. These organic-rich carbonates are unique in their relatively low diagenetic stage, a wide range of porosity (5-35 %), and early thermal maturation (from immature to early oil window). The observed relationships are quite robust based on the high-quality laboratory and log data. However, our conclusions may be limited to the early stage of maturation and diagenesis of organic-rich carbonates, as at higher maturation and diagenesis the changes in physical properties can vary significantly.