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

Measuring Systems

Classical Heatflow

The Heatflow Probe is an instrument for the measurement of the thermal gradient and the thermal conductivity. With both parameters the heat flux density can be determined. The instrument is capable to measure in-situ values with 22 sensors down to a depth of 6 m below the seafloor. Besides the temperature sensor string, an extra heating wire is attached to the probe. That wire provides a heat pulse for the measurement of thermal conductivity. In summary the temperature gradient is measured along 22 points with a resolution of 0.001 K and in addition 22 in-situ values of thermal conductivity, and hence, the heat flux density is determined in one go. Download Flyer HeatFlowProbe (engl.) (pdf-file)

The FIELAX HeatFlowProbe (6000 m or 10000 m) is also available for purchase.

Please find our product description for more information or contact Download Product description FIELAX HeatFlowProbe (engl.) (pdf-file).


For in-situ temperature and thermal conductivity measurements in shear resistant marine sediments, typical for shallow seas, coastal and continental shelf regions, FIELAX GmbH combined the functional components of the FIELAX HeatFlowProbe with a VKG6 type Vibrocorer. We name this new measuring device “VibroHeat”. With the ability to penetrate even through harsh layers such as gas hydrates, permafrost soils or “sands”, the technical application is not restricted to soft sediment conditions anymore. Download Flyer VibroHeat (engl.) (pdf-Datei)


In cooperation with Marine Sampling Holland, FIELAX has further developed its heatflow measurement system to work with a CPT unit used for in-situ geotechnical measurements, in order to overcome possible liquefaction, which may occur in very sandy sediments due to the vibrocoring. Therefore the sensorstring was adapted to fit into a standard coiled CPT-tube of 6 m length i.e. the number of temperature sensors was reduced to 13 temperature sensors at a spacing of 42 cm.

Principle of Measurement

The FIELAX heatflow measuring system records temperature as a function of time. The temperatures are recorded with 22 thermistors that are placed within a sensor string. The sensor string also contains a heating wire with which a distinct amount of energy is released into the sediments.

  • A: lowering to seabed
  • B: penetrating into seabed
  • C: measuring thermal decay of frictional heat
  • D: heat pulse
  • E: measuring thermal decay of heat pulse
  • F: pullout and retrieve to surface