FIELAX presents its latest development: 2D and 3D temperature evolution calculations in marine sediments. The models incorporate the geothermal heat flow, 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:

Heat Flow Services

Heat flow measurement and data interpretation

We offer worldwide heat flow measurements for marine research and offshore industries as well as data interpretation.

A typical heat flow measurement campaign covers:

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

The resulting dataset of a heat flow measurement station typically contains:

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

Heat Flow Products

Classical Heat Flow

The Heat Flow 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)

Heat Flow Probe Plus: Latest 2016 version
Download Flyer HeatFlowProbe Plus (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 heat flow 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. Read more…

Temperature Gradient Probe

The Temperature Gradient Probe measures temperature profiles in the sediment with temperature loggers mounted along a massive steel lance. The data acquisition using those loggers is operating in an autonomous way. The robust layout of the probe provides a large penetration depth of more than 5 m, quite more than with conventional instruments in use today. With this penetration depth reliable results are achieved and the uppermost, thermal disturbed, sediments are not falsifying the experiment.

What is heat flow?

The term ‘geothermal heat flow’ refers to the thermal energy that dissipates constantly from its sources within the earth to the surface, either by convection or conduction. Geothermal heat is the driving force for a variety of multi-scale geologic processes taking place in the earth’s crust e.g. plate tectonics. It is also driving chemical reactions like the thermal degradation of organic matter, which leads to hydrocarbon (oil and gas) formation. The internal temperature of the earth increases with depth. Near the surface, the average geothermal gradient is relatively constant with on average 30 K for every kilometer of depth. However, there are also places where it can be higher e.g. along mid-ocean ridges or mantle plumes.

How is heat flow determined?

Even though called heat flow measurements, heat flow itself is not measured directly. But based on the assumption, that heat conduction is the dominant transport process through the earth´s crust, and conductive heat flow occurs in the direction of decreasing temperature, heat flow can be calculated as the product of the vertical thermal gradient and thermal conductivity (Fouriers law). If however other mechanisms like heat advection are involved (for example fluid flow processes), heat transport may be characterized by non-linear thermal gradients and also occur horizontally.

What is the use of heat flow measurments?

In the field of petroleum geology heat flow measurements are essential in the exploration of new oil and gas reservoirs, as they provide critical constraints for sedimentary basin modeling and aid in thermal maturity calculations. Heat flow measurements also enable stability analysis of gas hydrate deposits.

The booming offshore wind energy market has opened a new field of activity for heat flow measurements, as in particular thermal conductivity values provide useful information for estimating the dissipation mechanisms of thermal energy and also the environmental impact of power cables.

Read our “Heat Flow” (PDF) and “Prediction of Sediment Temperatures” (PDF) brochures for detailed information: