Monitoring and forecasting failure in laboratory using coda wave decorrelation

Abstract

Gas extraction has caused pressure differences along the field, triggering earthquakes, which are causing a lot of damage and social unrest in the Groningen area. Predicting the degree of these stress changes, and as a result, the potential onset and exact location of failure and seismicity, is very challenging.

Therefore, developing good techniques that can monitor these changes is crucial for a better prediction and thus mitigation of failure and seismicity in the subsurface. Laboratory active acoustic-monitoring techniques are used to determine parameters that can forecast upcoming failure and seismicity.

We show the use of coda wave decorrelation as a monitoring tool using sandstones analogues for the Groningen reservoir. Failure of the rock sample is preceded by the formation of micro-fractures. These fractures change the scattering properties of acoustic waves. The decorrelation coefficient K, as the indicator of the amount of scattering and thus be used as precursor to failure. We show that by monitoring K we can forecast the upcoming failure of the rock samples in the laboratory.