Kring Noord KNGMG: lezing februari
KNGMG kring Noord lezing heeft als onderwerp:
“Acoustic Detection of Fault Dynamics; Monitoring Fault activity prior to large scale movement”. De lezing wordt gepresenteerd door prof. Auke Barnhoorn (TU Delft).
In subsurface operations (such as geothermal energy, CO2 storage or hydrocarbon production), but also in ore mining activities and for concerns of structural integrity of structures (e.g. building, bridges), being able to detect when material integrity is compromised, thereby inducing a seismic event, is crucial. Thus, if we are able to forecast when a intact material starts to fail or when pre-existing faults are being reactivated, we may enable ourselves to start forecasting when seismicity is about to occur.
Our research at the TU Delft focuses on laboratory studies in which we test, at a lab-scale, whether monitoring techniques can be used to forecast that failure and fault reactivation is imminent. We do this by continuously sending seismic waves through rock samples that we deliberately bring to failure. We have recently shown in these experiments that with active acoustic monitoring, we can use the time-lapse changes in characteristics of the recorded acoustic waves to detect the nucleation and growth of micro-fractures in a material under stress, as well as the onset of fault reactivation.
In this presentation, I show how we combine the changes in acoustic velocity during deformation, the changes in the characteristics of the wave forms (e.g. wave amplitude), as well as decorrelation analyses of two consecutive waveforms, to detect the progressive changes in the material, thereby forecasting failure (both failure of intact materials and re-activation of pre-existing fault structures). I will also discuss the possibilities, uncertainties and limitations of using this developed monitoring strategy for the minimization/mitigation of seismicity in subsurface operations or for integrity monitoring of structures.
Over de sprekers:
Auke Barnhoorn holds a tenured Associate Professor position in Applied Geophysics and Petrophysics at the Department of Geoscience and Engineering at Delft University of Technology (The Netherlands). His main research interests are rock physics and rock mechanics and fracture network development. He uses experimental facilities in Delft to study the anisotropic properties of rocks combining geomechanical and acoustic measurements and 3D imaging of the rock structures. His research has applications in e.g. geothermal energy, CO2 storage and induced seismicity. Auke is educated at Utrecht University in the Netherlands where he holds a MSc in geology and at ETH-Zürich (Switzerland) where he received his PhD. After his PhD he had post-doc positions at the Australian National University in Canberra (Australia) and at Utrecht University in The Netherlands.