Extension of Duplexed Single-Ended Distributed Temperature Sensing Calibration Algorithms and Their Application in...

Area of Science:

• Geophysics
• Earth Sciences
• Instrumentation

Background:

• Fiber-optic distributed temperature sensing (DTS) is crucial for precise thermal measurements in diverse applications.
• Environmental and deployment factors significantly influence DTS accuracy.
• Existing DTS calibration methods require enhancement, particularly for geothermal applications lacking end-of-cable temperature data.

Purpose of the Study:

• To evaluate a duplexed single-ended DTS calibration algorithm.
• To extend DTS calibration for scenarios without end-of-cable temperature information.
• To assess geothermal gradients in the Atacama Desert and Central Andes Mountains.

Main Methods:

• Laboratory experiments to assess DTS calibration algorithms.
• Field testing of extended algorithms in boreholes.
• Comparison of new algorithms against manufacturer standards.

Main Results:

• The optimized algorithm achieved a root mean square error of 0.31 ± 0.07 °C at the far end of a ~1.1-km cable.
• This represents a significant improvement over the manufacturer's algorithm (2.17 ± 0.35 °C).
• Temperature differences between single- and double-ended measurements were below 0.3 °C, yielding geothermal gradient differences of ~0.5 °C km⁻¹.

Conclusions:

• The developed DTS calibration algorithms provide more accurate geothermal gradient estimations.
• Improved accuracy can reduce drilling depth by at least 700 m in the study regions.
• Future research includes algorithm extensions for other DTS configurations and flow rate determination.