Spatial Analysis of Seismic Stress Drop at the HDR Soultz Geothermal Site

Abstract

Variograrn analysis for stress drop from induced seismicity generated during injection experiment at HDR- Soultz geothermal site in France was performed. The objective of the study was to examine the relationship between spatial variability of stress drop and distribution of joint and fracture zones within a granite reservoir. For a selected slice of 60 meters thickness and horizontal extension over the whole reservoir a set of directionalvariograms was computed both along horizontal and vertical planes. Several variograms exhibited spatial correlation of stress drop along certain directions which could be then associatedwith the direction of the maximum horizontal stress or strike and dip of the main joint sets at derived other measurements. The suggested methodology offers a potential to gather some quantitative information about structural features within a reservoir by analysis of seismic source parameters.