Diagenesis and Pore Pressure Induced Dim Spots – Advances on AVO Analysis of High-Impedance Reservoirs

We introduce a pressure-dependent rock physics model for shales and sands to analyze the effects of pore pressure and diagenesis on high-impedance reservoirs. With datasets at multiple scales (plugs, logs, and seismic) we show how diagenesis and composition combination impacts the seismic analysis on Brazil’s northeastern equatorial margin. This workflow combines established rock physics theories and models with data-driven analysis of geophysical properties. We perform AVO analysis using synthetic seismic data generated from our rock physics model and compare it to the field data through 3D seismic interpretation. The modelling of our equatorial margin dataset shows that high pore-pressure settings cause amplitude reduction and potentially a shift between class-I and class-II AVO. In our 3D seismic interpretation, we attribute amplitude dimming to differential diagenesis, increasing rock’s porosity, and lowering bulk density. We propose the diagenetic dim spot as a potentially valuable concept for exploratory campaigns in high-impedance reservoir plays.