Distributed Acoustic Sensing – a new tool for seismic applications

TLDR

Distributed optical fibre sensors are widely used in the energy industry for production optimisation and integrity monitoring, and the recent introduction of Distributed Acoustic Sensors (DAS) extends their application to seismic imaging. This study presents the iDAS, a new DAS instrument, and demonstrates its signal quality and performance through a series of laboratory experiments. The authors validate the iDAS by comparing its data with conventional point sensors, conducting lab experiments that confirm key performance metrics, and performing field demonstrations that include event localisation and acoustic imaging via a single‑fibre acoustic camera. Results show that the iDAS accurately records amplitude, frequency, and phase of acoustic signals along the fibre, and field tests reveal that iDAS measurements match or surpass geophone data, with shot‑record stacking improving offshore VSP survey quality.

Abstract

Distributed optical fibre sensors are established tools in the energy industry, finding many applications for production optimisation and integrity monitoring. Recently, a new class of instrument, the Distributed Acoustic Sensor (DAS), has been launched which adds seismic imaging to the list of energy industry applications. In this paper, we describe one such distributed acoustic sensor (named the iDAS) and demonstrate, through a series of lab experiments, the signal quality and performance that can be achieved. We show data which demonstrates the capability of the iDAS to measure the true acoustic signal (amplitude, frequency and phase) at all points along the sensing fibre length. We also compare the iDAS data with data collected from conventional point sensors and detail experiments which validate key performance criteria. We follow the lab experimental validation of the iDAS with a series of lab and field demonstrations. The lab demonstrations encompass localisation (ranging) of events away from the sensing fibre (for security applications) and acoustic imaging through the formation of a large acoustic camera using a single sensing fibre. The field demonstrations show comparisons of iDAS and geophone measurements in a surface seismic survey and improvements made by stacking shot records from an offshore VSP survey.