The Self-Potential Response During Hydraulic Fracturing of Sierra Granite

Abstract

The self-potential (SP) response during hydraulic fracturing of intact Sierra granite specimens was investigated in the laboratory. Excellent correlation of injection pressure and SP suggests that the SP response is created primarily by electrokinetic coupling. For low injection pressures the variation of SP and pressure drop is linear indicating a constant coupling coefficient (Cc). However, for injection pressures >2MPa the Cc increases with pressure by nearly 80% in an exponential trend. The increasing Cc is likely related to increasing permeability at high pore pressures due to dilatancy of micro-cracks.