Distributed Temperature Sensing (DTS)
Distributed Temperature Sensing DTS System
In distributed temperature sensing fiber optic systems, light is sent down the fiber string, and a specific portion of the light is scattered due to the impurities within the fiber string. This light distribution is known as Rayleigh backscatter.
The wavelength of the light changes once scattering of the light occurs, which can then be broken out into two different types, Stokes and Anti-stokes scattering. Stokes scattering (longer wavelength) is not heavily influenced by temperature, compared with anti-stokes scattering (shorter wavelength). The intensity of the anti-stokes scattering increases with temperature, where-as the stokes scatter intensity is much less affected.
Fiber temperature measurement is determined by the difference between stokes and anti-stokes intensity. The depth of the temperature change is determined by the time it takes for the scattered light to return to the light source, or interrogator, leading to precision in our distributed temperature sensing fiber optic systems.
DTS – Benefits and Uses in Oil and Gas
Plug Failure Determination: During stimulation operations, the temperature profile of the zone below the plug should be in a warm-back state, based on fibre temperature measurement.
If cooling is noted below the plug, there is either communication behind casing, or the plug has failed. Using distributed acoustic sensing data in conjunction with distributed temperature sensing dts systems allows the operator to make a more informed decision on plug failure when referencing any acoustic signatures, corresponding with the temperature change.
Pipeline Integrity: Fiber is becoming more commonplace for pipeline integrity monitoring, vs. smart pigging or pressure monitoring. Utilizing a distributed temperature sensing dts system when the pipeline is installed will enable the operator to pinpoint a leak along any section of the pipeline, using fiber temperature measurement. The fluid within the pipeline will normally be higher than the ambient temperature, notifying the operator of a change.
Stimulation Optimization: During fracture operations, distributed temperature sensing fiber optic systems can be used to determine where the fluid is moving within the stimulated stage. The added benefit of DTS is the warm-back feature which is monitored post-stimulation. This allows the operator to better understand fluid distribution across the stimulated stage.
Well Productivity: On flowback operations, inter-stage production contribution can be better understood with the fibre temperature measurement and changes along the fibre. Nominal resolution of the fibre is ~ 1m for most applications.
Fibre Temperature Measurement, During Fracture Operations
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