Dynamics of Stick-Slip Sliding Induced by Fluid Injection in Large Sandstone Block: 80th EAGE Conference and Exhibition 2018

Safe geologic sequestration of CO₂ is important to decrease the concentration of greenhouse gases in the atmosphere. However, the injection could increase the underground pore pressure and potentially induce sliding of critically stressed faults. We report results from a laboratory test where fluid injections close to an artificial interface of ~1m length were observed to induce sliding. During the injection, the pore pressure at the injection point reached up to 6.2 MPa and after shut-in, it dropped down to almost zero. However, about 10 minutes later, a sudden sliding of the interface (stick-slip motion) was recorded. Two types of acoustic emission (AE) signals were detected: short bursts and long-lasting oscillations (tremors). The analysis of the spatial distribution of the AE energy was applied to monitor the dynamics of stick-slip, indicating a nucleation phase of the sliding, then the rupture propagated through the whole interface with an average rupture velocity of a few m/s. The speed and the energy radiated during this event were approximately 6 orders of magnitude larger than observed during quasi-static sliding preceding the stick-slip. This observed stick-slip motion can be considered a laboratory analogue to earthquakes, and its occurrence can be related to the injection of fluids.