Field Trial of a Broadside-sensitive Distributed Acoustic Sensing Cable for Surface Seismic

Distributed Acoustic Sensing (DAS) for seismic applications is a relatively new technology. It is based on the measurement of strain by means of Rayleigh back-scattering by inhomogeneities in an optical fibre. DAS for seismic is promising, because the sensing cable does not require any power and it is potentially low-cost. In addition, the sampling along the cable can be adapted to the geophysical needs in the field by a setting in the Interrogator Unit. Successful seismic DAS applications have been shown earlier for Vertical Seismic Profiling. A limitation of current DAS cables is that they are insensitive in the broadside direction, perpendicular to the cable, making them unsuitable for reflection seismic with a horizontal cable, as used in surface seismic. In this paper we describe a novel DAS cable with broadside-sensitivity. Such a cable was manufactured and a field trial was carried out to validate the theoretical predictions of its angular sensitivity, by comparing this cable with 3C accelerometers. The results indicate that the cable is indeed sensitive in all directions - to our knowledge a first in the industry. This property enabled the acquisition of seismic reflection data at the surface with a horizontal DAS cable.