Quantifying Thermal Conductivity Along Offshore Wind Farm Cables by Combining Geophysics and Geostatistics

Offshore wind farm cables are normally buried in the seabed for mechanical protection, but this also insulates them. During operation the cables will heat up because of the power being transmitted and it is important to understand how much heat transfer will occur through the surrounding backfill. Heat transfer for most soils depends on thermal conductivity. Consequently, understanding the distribution of thermal conductivity along a proposed cable route is critical.

Thermal conductivity depends on the type of soil, its density and its structure. Consequently, this is often measured using intact soil samples taken from the seabed or through in situ testing (using thermal cones) at widely spaced discrete locations. Therefore, one key design question is how to quantify the variability of the thermal properties along a cable route due to natural soil variability that may not be full characterized using measurements at discrete locations. How can seabed zonation help the design?

The above questions are addressed using statistical frameworks originally developed for providing mechanical inputs to pipeline projects coupled with recent findings from work using geophysical inversion alongside a database of thermal conductivity testing. The framework be explained and example results from one section of carbonate seabed will be shown.