Heat conductivity and temperature diffusivity

For many years, the thermal conductivities of sediments have been calculated at FIELAX from the data of special temperature measurements. For many applications, however, the thermal diffusivity is also of interest. Together with the University of Bremen it was investigated how the calculation of thermal diffusivity from temperature data in addition to thermal conductivity can be achieved or improved. As a result of this project, which was supported by the European Regional Development Fund (ERDF), a scientific publication was produced, which is available at https://doi.org/10.1007/s13137-021-00183-1.

TRT measurements Off-/Near-/Onshore Holland – cooperation with Next Geosolutions and Marine Sampling Holland

Since December 2020 and ongoing, FIELAX provides thermal conductivity / thermal resistance measurements for cable routes for three wind zones in the Dutch North Sea to be connected by TenneT (offshore-energy.biz/tennet-picks-next-geosolutions-for-route-surveys-fugro-as-backup/). As a subcontractor to Next Geosolutions (nextgeosolutions.com), FIELAX conducts most of the surveys using our systems in combination with Next's Vibrocorer.

At shallow water depths / tidal flats / onshore, the VibroHeat method is not feasible. We are pleased to offer different adapted deployment methods with different geotechnical equipment in close cooperation with Marine Sampling Holland (marinesamplingholland.nl). Some nearshore and - so far - all onshore tests have been performed with the PushHeat system (a combination of a mini-CPT with a coiled thermal test rod; the picture shows one site on the beach on a stormy day). In 2021, we also expect to deploy downhole technology for onshore locations where a high-resolution TRT profile is required to depths greater than 10 meters. To reach these depths, multiple cycles of drilling/probing will be performed. More information on the methods and additional references can be found at www.fielax.de/en/what-is-heat-flow/.

Modelling

FIELAX presents its latest development: 2D and 3D temperature evolution calculations in marine sediments. The models incorporate the geothermal heatflow, measured thermal properties of the sediments as well as temperature variations through seasonal variations of the bottom water temperature. As a result the models determine temperature distributions resulting from superimposition of seasonal, natural temperatures and those induced by internal sources such as power cables, the latter also time-dependent.

  • The Cable Route Model is a full model for the temperature field in and around submarine power cables. The model includes heterogeneous properties of the sediments, seasonal heating and cooling through bottom water temperature variations, and heating thgough time-dependent power loss from the cable. Applications are the 2k-criterion or the dimensioning of subsea power cables (PDF-Flyer).
  • The 3D temperature model has been developed to calculate temperature fields in marine sediments or onshore soil. Given inputs are measured thermal properties and approximated seasonal temperature deviations of the water/air. Thus, the seasonal effects as well as influences from heat sinks- and sources (such as energy cables or heat exchangers) may be modelled.

Read our “Prediction of Sediment Temperatures” (PDF) brochure for detailed information:

Heatflow & TRT Services

Heatflow measurement and data interpretation

We offer worldwide heatflow measurements for marine research and offshore industries as well as data interpretation using our different systems.

A typical heatflow measurement campaign covers:

  • Rental or sale of equipment and optional delivery/freight
  • Experienced and safety trained offshore surveyors
  • Operation of the heatflow instruments on board during station work
  • Preliminary data quality check on board
  • Data interpretation and analysis on land

The resulting dataset of a heatflow measurement station typically contains:

  • Temperatures over penetration depth and time
  • Thermal conductivities over penetration depth
  • Specific heat capacity over penetration depth
  • Calculated heatflow of the station