Towards Good Practice of Cable Layout for Surface Distributed Acoustic Sensing

Session: Photonic Seismology
Type: Oral
Date: 4/30/2020
Time: 09:00 AM
Room: 215 + 220
Description: 

Distributed Acoustic Sensing (DAS) has the potential to significantly uplift high-resolution ground-motion data acquisition capabilities by interrogating a single low-cost optic-fiber cable instead of using numerous cost-intensive point sensors. DAS is emerging as a cost and logistic effective seismic tool for broad-band geo-hazard and reservoir monitoring.

The reliability of DAS-based Vertical Seismic Profile acquisition is now widely recognized when the cable is adequately coupled with the borehole casing. At the surface, however, for reflection seismic for example, the adequate deployment procedure is less clear, and field experiments are achieved with the cable sometimes directly on the surface and sometimes buried quite deep in trenches. The excavation effort can be prohibitive for instance due to cost and permitting issues.

To clarify if such an effort is actually required, we performed a surface active field experiment with a controlled vibroseis source and compared the repeatability of the DAS measurements from “co-located” stretches of cable deployed at different depths. The study shows that deep burial provides minimal quality improvements compared to shallow deployment. However, data from the cable directly at the surface exhibit unacceptable noise levels, suggesting that covering the cable with a small amount of elastic material provides an acceptable coupling and therefore consists of an affordable, convenient field practice.

Presenting Author: Pascal Edme

Authors