Effects of temperature on DAS measurements

Abstract

Summary Distributed acoustic sensing(DAS) and Distributed Temperature Sensing(DTS) are being actively used in various exploration and monitoring applications. DTS is used for measurements and monitoring of the temperature and DAS is used for recording seismic wavefield. At the same time, DAS measurements are sensitive to temperature changes. The response of DAS to temperature is proportional to a time derivative of temperature as DAS naturally measures strain. Understanding of how DAS measurements can be affected by changing temperature is paramount to avoid or/and eliminate noise related to temperature variations. This can be particularly critical for the DAS time-lapse seismic and passive monitoring. We utilised the Curtin/NGL research facility and Rock-Physics Laboratory to estimate temperature’s effect on three various DAS cables. Two different fibres were tested in the laboratory and one cable (installed in the Curtin/NGL well), examined at the site. We demonstrated that DAS is sensitive to temperature changes and its response is proportional to a time derivative of temperature. Our study shows that by using DAS and temperature data together, it is possible to estimate strain – temperature change dependency (microstrain/degree) for a particular cable. Coefficients estimated in three tests indicate that cable type/design can affect DAS response to temperature changes.