Seismic velocity changes in the Groningen reservoir explained at LC Netherlands meeting

Dong Zhang (EAGE Local Chapter Netherlands) writes: A live event in April at the new Echo building in Delft University of Technology (TU Delft) featured Dr Wen Zhou from the Department of Applied Geophysics. It was hosted by the EAGE Local Chapter Netherlands (since awarded Best Local Chapter of the Year at the recent EAGE Annual).

Dr Zhou was invited to talk about seismic velocity changes associated with distant drilling in the Groningen reservoir, the largest natural gas field in Europe and one of the largest in the world. He began a general introduction about distant induced earthquakes, with examples from Strasburg and Groningen, and the potential mechanisms behind them. In terms of passive reservoir monitoring, reservoir pressure diffusion could be an indicator of different mechanisms.

Dr Zhou asked the question: can seismic waves, e.g., borehole seismic data, be used to monitor pressure changes? By way of answer, he offered a detailed description and elaboration on a related research project on passive seismic reservoir monitoring in Groningen. This consisted of ambient-noise interferometry, train-noise interferometry, P-wave timelapse variation, and S-wave timelapse variation. Dr Zhou concluded that P- and S-velocity changes are observed using repetitive train noise, and the changes are correlated with drilling that produced overpressure in the reservoir. He also mentioned that ambient-noise level changes can be found.

Questions from the audience and enthusiastic discussion followed after the talk. It seemed most audiences were curious about the train-noise interferometry. Some were left wondering whether more trains from opposite directions or stranger signals from trains would help. Others were curious about the best practice for the correlation of signals. There was also a comment from the audience about the fault model.

This live event was a success thanks to the great effort and contribution of the speakers. The event is available on the EAGE YouTube channel for anyone interested in this exciting new technology. Stay informed about the Chapter activities through their LinkedIn page.