Ground surface temperature reconstructions: Using in situ estimates for thermal conductivity acquired with a fiber-optic distributed thermal perturbation sensor

We have developed a borehole methodology to estimate formation thermal conductivity in situ with a spatial resolution of one meter. In parallel with a fiber-optic distributed temperature sensor (DTS), a resistance heater is deployed to create a controlled thermal perturbation. The transient thermal...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Freifeld, B.M., Finsterle, S., Onstott, T.C., Toole, P., Pratt, L.M.
Language:unknown
Published: 2009
Subjects:
54
58
BOREHOLES
HEATERS
PERMAFROST
SPATIAL RESOLUTION
THERMAL CONDUCTIVITY
TRANSIENTS
Nunavut
Canada
High Lake
permafrost
Online Access:http://www.osti.gov/servlets/purl/951790
https://www.osti.gov/biblio/951790
https://doi.org/10.1029/2008GL034762
Description
Summary:We have developed a borehole methodology to estimate formation thermal conductivity in situ with a spatial resolution of one meter. In parallel with a fiber-optic distributed temperature sensor (DTS), a resistance heater is deployed to create a controlled thermal perturbation. The transient thermal data is inverted to estimate the formation's thermal conductivity. We refer to this instrumentation as a Distributed Thermal Perturbation Sensor (DTPS), given the distributed nature of the DTS measurement technology. The DTPS was deployed in permafrost at the High Lake Project Site (67 degrees 22 minutes N, 110 degrees 50 minutes W), Nunavut, Canada. Based on DTPS data, a thermal conductivity profile was estimated along the length of a wellbore. Using the thermal conductivity profile, the baseline geothermal profile was then inverted to estimate a ground surface temperature history (GSTH) for the High Lake region. The GSTH exhibits a 100-year long warming trend, with a present-day ground surface temperature increase of 3.0 {+-} 0.8 C over the long-term average.

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