Seismic time‐lapse velocity variations in the Groningen subsurface

Obtaining relevant information about subsurface properties is often difficult or expensive. Ambient-noise passive image interferometry (PII) is a low-cost technique that potentially offers great possibilities. With PII changes in seismic velocity can be monitored. We investigate the feasibility of using PII to obtain information of underlying subsurface properties responsible for the measured velocity variations.
As an example, the temperature impacts seismic velocity. If the yearly variability of the temperature field can be unraveled using PII, knowledge about thermal conductivity can be obtained. We have the availability of data from several arrays of geophones in Groningen. These data are processed to extract seismic velocity variations. We are thus investigating the correlation between velocity and other physical parameters like stress, temperature and saturation. If such an identification appears feasible, we expect that -with the right configuration- we can indeed make an inversion, e.g., to obtain thermal parameter distributions.
We have devised a forward model that mimics how stress and temperature change the velocity inspired by the subsurface above the Groningen gas field. We compare the results with the velocity variations, obtained with PII.