VSP Using Distributed Acoustic Sensing with Scatter-Enhanced Fibre-Optic Cable at the New Afton Porphyry Deposit, Canada

We present vertical seismic profiling results acquired with distributed acoustic sensing (DAS) in boreholes that intersect the main mineralized zone and alteration halo at the Cu-Au New Afton porphyry deposit, Canada. We used an advanced DAS system achieving signal-to-noise ratio of conventional geophones but offering high-density sensing of the entire fibre-optic cable. Straight and helically-wound fibre-optic cables specifically engineered for that system were installed in two boreholes and compared to conventional fibre-optic cables with similar configuration connected to a standard interrogator. Comparison of raw field and processed data demonstrates significantly higher signal-to-noise ratio for the new DAS system. Upgoing waves in one of the boreholes reveals a strong reflection near the bottom of the fibre-optic cable and another slightly below it. These reflections are associated with biotite-dominant potassic alteration zone and picrite, and are excellent proxies for the top and bottom of the hypogene mineralized zone.