Observed Anisotropic Effects of Fractures in a Hot Dry Rock Geothermal Reservoir by Shear-Wave Polarisation Analysis

Summary The paper focuses on a VSP 3-C analysis for shear-wave polarisations characterisation in a hot dry rock geothermal reservoir, Cornwall UK. We analysed the clear high amplitude direct S wave arrival recorded by our high fidelity 3-C geophone tool string which showed excellent data quality on horizontal components. One of the objectives was to evaluate the coherency of the shear-waves polarisations in respect to the maximum stress direction and strike-slip faults that were detected during hydraulic stimulations experimental work at Rosemanowes quarry a Carnmenellis granite environment drilled in the 80s. On this site, hydro-fracturing were proved to be almost irrelevant, and the granite rock was dominated by natural fracture system. Additionally, we qualitatively showed that stress fields in crystalline rock are invariably anisotropic using shear wave splitting analysis.