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 ( As a subcontractor to Next Geosolutions (, 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 ( 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


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.