Frequency‐dependent signal‐to‐noise ratio effect of distributed acoustic sensing vertical seismic profile acquisition

Distributed acoustic sensing provides seismic sensors distributed every few metres over each fibre optic cable of several kilometres in length, serving as an ultra‐dense array for both surface and downhole seismic acquisitions. It is well‐recognized now that distributed acoustic sensing acquisition configuration can have profound effect on data quality, notably the choice of the gauge length and lead‐in cable length on the resulting signal to noise ratio. In this paper, we present a detailed study on how these effects behave differently over various signalling frequency bands. We derive the signal to noise ratio as a function of the peak frequency, gauge length and lead‐in cable length, and demonstrate significantly different 80 SNR samples behaviours over low, middle and high frequency bandwidths, respectively. These results, not only reveal the underlying mechanism for signal and noise variation as function of acquisition parameters, but also help identifying the desired gauge and cable lengths that better serve particular applications, such as inversion and imaging which take information from different frequency bands. A field data has been used to demonstrate these frequency‐dependent behaviours.