Compensation of the temperature effect on low-frequency DAS measurements: Case study of the water injection at the Otway site

Abstract

Distributed acoustic sensing (DAS) is an emerging technology that has already found a widespread application in seismic acquisition and reservoir monitoring. DAS is designed to register acoustic vibrations, but it is also sensitive to temperature variations. The effect of temperature variations on DAS recordings can be observed as a low frequency signal (< 1Hz). It is critical to be able to separate the temperature effect on DAS records from seismic signals, especially if one is utilizing low frequencies for passive seismic measurements. In this study, we show how borehole DAS recordings can be affected by the temperature change during the water injection into a deep formation at the Otway site. Joint analysis of distributed acoustic and temperature sensing data shows that there is a linear dependency between the strain and slow temperature change. Using such relation, the temperature effect can be compensated.