Distributed fiber-optic sensing is a measurement technology that utilizes the phenomenon whereby the backscattering characteristics of laser light change in response to external influences such as “strain” and “temperature.”
The use of heat-resistant fiber-optic cables has enabled vibration measurement (DAS) and temperature measurement (DTS) in high-temperature geothermal Wells.
This technology is considered capable of capturing detailed spatial and temporal changes in the vicinity of the Well, and is deemed effective for monitoring Wellbore conditions that vary over time, such as those encountered after drilling.
Principle of distributed optical fiber sensor
TS and DAS monitoring data acquired in a geothermal well
In addition to records of acoustic emissions (AE) generated near the Well, the DAS data examples show that there are zones at both shallow and deep sections where the vibration levels remain consistently high. In the shallow zone, the area of vibration corresponds in the DTS record to the interval where the saturation temperature is reached, and the pronounced vibrations originating at the water level depth are interpreted as indicative of boiling. In zones with high vibration levels at greater depths, significant changes in the temperature curve are observed, suggesting a relationship to formation fluid activity.