MUSE pilot area activities – RESULTS – #13 Warsaw

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Preparation of a 3D model and shallow geothermal energy resource maps

Grzegorz Ryżyński, Przemysław Wojtaszek, Maciej Kłonowski (PGI-NRI), 7 October 2021

The activities accomplished within the MUSE project in the Warsaw pilot area, Poland, have focused on gathering and analysis of borehole data derived from the archival data sets as well as from the newly performed measurements of thermal properties of the soils, rocks and sediments. An appropriate GIS database, which was a basis for further 3D modelling, contains the following verified and unified data (Figure 1):

  • 4 geological cross-sections interpreted specially for MUSE Project 3D modelling purposes;
  • 21 archival geological cross-sections derived from the serial Detailed Geological Map of Poland in 1:50K scale;
  • 1,023 virtual boreholes derived from the archival geological cross-sections;
  • 882 virtual boreholes derived from 4 interpreted geological cross-sections;
  • 2,619 verified and reclassified boreholes derived from the databases run by the Polish Geological Institute – National Research Institute (PGI-NRI).
Figure 1. Borehole data in MUSE GIS database of Warsaw

The data sets have been used to generate an advanced 3D geological model of the studied area. The model consists of 15 geothermal units showing thermal conductivity parametrization for both wet and dry conditions (Figure 2). Geostatistical analysis, i.e. inverse distance weighting method algorithm (IDW), has been used in order to determine the units and their parametrization. Delineation of geothermal units in the form of unfied shape file polygons, showing verified topology has been an important part of the 3D modelling process. Thereafter, the layers have been applied to define the extents for further interpolation thus detailed modelling of geological surfaces has been possible.

Figure 2. Extent of the 15 geothermal units for the Warsaw pilot area, each showing verified topology. These GIS layers are used in the 3D modelling process.

The 3D model has been set-up with the software GOCAD allowing for modelling the bottom surfaces of geothermal units as TIN layers. Thereafter, the surfaces have been transferred as point clouds to a GIS software and rendered as 25 x 25 metres resolution raster grids, suitable for python map algebra calculations. Altogether, the digital elevation model, the groundwater table depth [m b.g.l.] and the geological raster grids have been reprocessed and used to generate a set of average thermal conductivity maps for selected depth intervals of 0 – 40, 40 – 70, 70 – 100 and 100 – 130 [m b.g.l.] (Figure 3).

Figure 3. Parametric 3D model (left) for the Warsaw pilot area showing a set of 15 geothermal units, the digital elevation model and a groundwater table depth [m b.g.l.]. The parametric model is necessary to calculate the final thermal conductivity maps for the selected depth intervals (right). 

In the Warsaw pilot area, the final average thermal conductivity values for the mentioned depth intervals (see an example in Figure 4.) correlate well with the elevation of top surface of the glacitectonically deformed pliocene clays in the Warsaw pilot area. Thermal conductivity is an important shallow geothermal energy resource parameter for closed loop systems (borehole heat exchangers). The maps illustrating the Warsaw project pilot area will be available via the GeoERA information platform (EGDI) and the PGI-NRI web GIS browser.

Figure 4. Example of shallow geothermal potential map showing average soil and rocks thermal conductivity value [W/m*K] for a depth interval of 0 – 40 metres for the Warsaw pilot area.

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