Three-Component Distributed Acoustic Sensing Arrays with Three-Dimensional Fiber Cable Deployment

We design two fiber distributed acoustic sensing (DAS) arrays to acquire three-component (3C) DAS array data. These two arrays are a cross array and a cross-concentric circle (CCC) array at the surface, with part of the fiber cable installed in a vertical wellbore. We calculate traveltimes from seismic sources to all fiber sensors of the DAS arrays and construct differential traveltime (DTT) profiles. We calculate the source azimuth and incidence angle from the spatial distribution of the differential times and then use the resulting angles to rectify the raw DAS amplitudes distorted by the fiber directivity. We create horizontal and vertical hodograms that are comparable to those of a 3C geophone at the DAS array center using the recovered amplitudes. Our DTT and waveform modeling results show that a 3D optimally distributed fiber cable can effectively acquire 3C DAS array data. Employing beamforming and coherent stacking techniques, we can significantly increase the signal-to-noise ratio (SNR) of the DAS system. This 3C DAS array overcomes three disadvantages of conventional DAS measurements: single component, fiber directivity, and lower SNR. Our 3C DAS array can also be used to monitor and study earthquakes and explosions at local, regional, and teleseismic distances.