Elastic Coulomb Stress Transfer during Injection Induced Seismicity
T. Kettlety, J.P. Verdon, J.M. Kendall and M.J. Werner
Event name: 80th EAGE Conference and Exhibition 2018
Session: Poster: Geomechanics A
Publication date: 11 June 2018
Info: Extended abstract, PDF ( 1008.86Kb )
Price: € 20
Determining the dominant physical processes occurring during injection-related fault activation is a vital component in the monitoring and mitigation strategies employed by numerous industries. Fluid processes (pore-pressure changes, poroelastic effects) are significant, though some recent studies have shown that stress interactions due to elastic deformation may contribute to further failure. Using a large microseismic dataset, acquired during the extensive downhole monitoring of a hydraulic fracturing operation, the elastic Coulomb stress changes are modelled for an identified period of fault reactivation. It was found that elastic stresses may have weakly promoted further failure during the initial phase of activity, after which stress changes generally acted to inhibit further slip. Taking into account the focal mechanism uncertainty (via bootstrapping permuted event geometries with a Von Mises distribution), the positive signal observed in this first activation period is still present though with a significantly reduced amplitude. Increasing the value of Skempton's ratio, simulating the presence of pressurised fluid, acts to further weaken the positive signal observed in the first period of activation. Thus, the initial modelling, as well as the sensitivity analysis, suggest that fluid effects most likely dominated the triggering in this case.