New wiggles from old cables: Data processing and imaging considerations

Abstract

Distributed acoustic sensing (DAS) using fiber-optic cables as sensors has become a standard measurement technique in many industrialized settings. Geophysical applications have been mainly commercialized in the borehole environment. When deployed on the seabed (SB), horizontal analysis of DAS data poses new challenges due to the particularity of the receiver response and characteristics of DAS data. Recent acquisition of a 2D towed-streamer (TS) survey following the path of a communication cable (installed in 1998), which is interrogated continuously throughout the TS acquisition, enables us to jointly analyze SB-DAS and conventional TS data recorded using modern hydrophone streamer from acquisition, through different processing stages up to a migrated image. The SB-DAS recording from the old communication cable enables us to generate excellent P-wave and converted wave (PS) images of the subsurface. However, care is needed when recovering the high spatial frequencies damped by the nature of DAS measurements (which also may depend on the hardware used) and demonstrating the recovery of the signal within the data processing (DP) sequence. Our focus is on the challenges associated with the DP of entrenched marine cables. Given a simple TS processing sequence as a reference, we examine an equivalent recommended practice for signal analysis, DP, and imaging of SB-DAS data.