How Karsts Presence Changes Seismic Velocities: Combining Digital and Physical Experimentations

Chemical dissolution creates intricate karst networks (small to very large wormholes) that significantly reduce the effective P-wave propagation velocity (Vp) of rocks. Quantifying their impact via seismic amplitudes is challenging due to the karsts’ size and the limited availability of rock physics templates.

This study addresses this challenge with a two-phase workflow: a digital approach (large scale) followed by physical sample measurements (small scale). Initially, full waveform seismic shots were simulated on digital reservoir grids with varying karst quantity and size. The second phase involved calibrating these results using physical 3D-printed replicas.

Results indicate a clear trend between karst density and bulk modulus. This trend notably differs from existing rock physics templates based on pore volume and shape, highlighting the need for new rock physics models specifically for epigenic karsts.

The paper will describe this promising method and its results for mapping and quantifying karst density, enhancing well placement for injection and production optimization.