Effect of Fluid Viscosity on Earthquake Nucleation
Chiara Cornelio, Marie Violay
Abstract
Abstract Injection of fluids in geo‐reservoirs can reduce the effective stresses at depth, lubricating the nearby faults, promoting slip and, potentially, earthquakes. High‐viscous fluids are often used during hydraulic fracturing and production phases in geo‐reservoirs. Here, we performed dedicated experiments to study the influence of fluid viscosity on earthquake nucleation. We performed frictional sliding experiments at 30 and 50 effective normal stresses and fluids viscosity ranging from 1 to 1,226 mPa s and modeled them with a rate‐and‐state friction law. In the presence of fluid, the state variable is defined as the ability of the fluid to flow. Our results showed that static friction slightly decreases with increasing viscosity, the dynamic friction is governed by the dimensionless Sommerfeld number ( S = 6 ηVL /( σ ' n H 2 ) ). Moreover, we observed that the ( a − b ) parameters of the rate‐and‐state friction law decrease with increasing viscosity down to ( a − b ) < 0, possibly promoting unstable slip and earthquake nucleation.