The Ragusa formation aquifer, located in south-eastern Sicily, is characterised by intense fracturing and karstification. Although it is a carbonate aquifer, it behaves like a clastic aquifer due to calcarenite deposits, which behave like calcareous sands. The aquifer is heavily used for drinking water, with numerous wells in the area. These wells and piezometric data were considered in this study.
A detailed methodology was defined for the quantitative use of geophysical logs from deep Oil & Gas wells to characterize the presence of groundwater in the Ragusa Formation starting from Electrical log inversion and following several steps. Based on geophysical log inversion, we obtained positive evidence and indications of the presence of fresh groundwater in the Oligo-Miocene aquifer of the Ragusa formation and its extension up to 10 km offshore. Based on electrical log inversion results, the next step was to refine and improve the previous static model and to transfer the petrophysical inversion into a static 3D property model. This allowed us to understand and observe how the petrophysical properties change both laterally and vertically within the Ragusa formation. Following these steps, we defined a 3D porosity and salinity model for the Ragusa formation.
Parallel to this work, several sessions were held on learning and writing Python code, and, with the help of guest speaker Daniel Zamrsky, several dynamic modelling sessions were run with different objectives, in order to understand the workflow. These sessions will be useful to better define the dynamic modelling of the Ragusa formation in the near future. In fact, the foundations were established for a dynamic model of the surface aquifer of the Ragusa Formation. Specific boundary conditions have been defined: head boundary and aquifer recharge conditions have been defined and the sea level varies up to a maximum of -120 metres from the current level (glacial-interglacial periods).
An initial dynamic model of the Ragusa formation was set up with the help of host Daniel Zamrsky. All inputs from the static model (porosity, hydraulic conductivity, permeability and groundwater heads) were considered.
The petrophysical results indicate two wells offshore at a distance of 10 km from the coast with a large presence of fresh water in the Ragusa formation at a depth of over -500 meters below sea level.
After the first dynamic modelling runs, though not yet mature, we can observe that the depth of the aquifer reaches -350 meters from sea level, thus very close to the actual value given by petrophysics, but not enough. Subsequent implementations dictated also by a better understanding of the Modflow and Seawat code and the Python coding, the results will certainly be much better. Future collaborations with Daniel Zamrsky are expected for the future construction and fine-tuning of the final dynamic model of the Ragusa formation.
The work on the Ragusa Formation, particularly with regard to petrophysical inversion, brings with it the discovery of as many as two offshore wells which show a presence of fresh water along the well at a depth from -500 below sea level to beyond.