Integration of VSP and TDEM data for hydrogeological characterisation

The hydrogeological characterisation often needs great detail and resolution to plan the drilling phase and to evaluate the possible interference between wells. We describe an integrated approach to analyse a complex formation of argillite and sandstone hosting an aquifer of great interested for mineral water supply: Time Domain Electromagnetic and borehole seismic methods are used.. Electromagnetic and electrical tomography measurements from the surface allowed estimating the geological set-up of the area for the optimal positioning of the borehole. The subsequent VSP (vertical seismic profiling) permitted to analyse the main fractured zones inside the sandstone: a full-wave analysis is performed to improve the resolution and reliability of the seismic data. The paper introduces some aspects of seismic data processing to separate and analyse the different wavefields involved in the VSP measurements.