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:
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.
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.
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
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
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.