Geological modelling for investigating CO2 emissions in FlorinaBasin, Greece

This paper presents an investigation of naturallyoccurring CO2 emissions from the Florina natural analoguesite in Greece. The main objective was to interpretpreviously collected depth sounding data, convert theminto surfaces, and use them as input to develop, for thefirst time, 3D geological models of the Florina basin. Byalso locating the extent of the aquifer, the location of theCO2 source, the location of other natural CO2 accumulations,and the points where CO2 reaches the surface, wewere able to assess the potential for CO2 leakage. Geologicalmodels provided an estimate of the lithological compositionof the Florina Basin and allowed us to determinepossible directions of groundwater flow and pathways ofCO2 flow throughout the basin.Important modelling parameters included the spatial positionsof boundaries, faults, and major stratigraphic units(which were subdivided into layers of cells). We used variousfunctions in Petrel software to first construct a structuralmodel describing the main rock boundaries.We thendefined a 3D mesh honouring the structural model, andfinally we populated each cell in the mesh with geologicproperties, such as rock type and relative permeability.According to the models, the thickest deposits are locatedaround Mesochorion village where we estimate thataround 1000 m of sediments were deposited above thebasement. Initiation of CO2 flow at Florina Basin couldhave taken place between 6.5 Ma and 1.8 Ma ago. The NESWoriented faults, which acted as fluid flow pathways,are still functioning today, allowing for localised leakageat the surface. CO2 leakage may be spatially variable andepisodic in rate. The episodicity can be linked to the timingof Almopia volcanic activity in the area.