FRANC

Title

Borehole-based FRActure uNClogging experiment: bridging the gap between laboratory- and field-scale evidence (FRANC)

In brief

There is evidence to suggest that seismic waves from distant earthquakes are capable of creating sufficiently strong pressure gradients to change permeability in the subsurface by mobilizing colloids that are blocking flow paths. So far, the only attempts to reproduce the effects of this so-called seismically induced unclogging mechanism were performed in laboratory experiments at small scales. Our experiment consists of applying a series of fluid pressure oscillations in selected intervals of a borehole crossing pre-existing fractures while monitoring the evolution of the overall permeability. The proposed intermediate-scale experiment is conceptually analogous to the small-scale laboratory experiments, which, in turn, allows for a direct comparison of results and opens the perspective of extrapolating them to the larger field scale.

Gaining knowledge on the seismically induced unclogging mechanism will have an impact on the interpretation and conceptualization of seismically triggered phenomena, which range from water level changes in wells to the triggering of volcanic and seismic activity. The experiment will be accompanied by a set of time-lapse geophysical borehole logging measurements as well as micro-seismicity monitoring. This will provide new and valuable insights on whether and how fracture unclogging can be detected and monitored using non-invasive geophysical techniques.

Duration

12 months

Project leader

Nicolas Barbosa

Funding

Spark Grant of the Swiss National Science Foundation