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AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop

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Ultra-Deep Geothermics In The Po Plain: A Preliminary Study On The Malossa Area


Ultra-deep geothermics is currently considered an interesting possibility to get high temperatures (>150 °C) that could be used for industrial applications. This kind of projects are starting currently in the Netherlands, in Belgium and in Germany, with promising perspectives. In this study, we analyse the possibility of ultra-deep geothermics in the Po Plain, close to Milan, by using public subsurface data in the Malossa area. The Malossa oilfield was discovered in 1973 and the production ended in the late ‘80s and produced gas and condensates. This project is focused on three stratigraphic/aquifer targets: the Dolomia Principale, Zandobbio Formation and Maiolica Fm. These units show very variable porosity, between 1% - 6% (average 3%) in Dolomia Principale, 1% - 13% (average 2,5%) in Zandobbio Fm., while the Maiolica has relatively negligible porosity. The reservoir permeability is related to fractures, as the matrix permeability is relatively low (50 mD in the Zandobbio Fm). Production tests showed very good productivity for the wells, with 500000 smc/day of gas and 2800 bbl/day of oil; unfortunately, by the moment, the publicly available data are not allowing any estimation of Kh from the wells. The available BHT, indicates temperatures (corrected) between 150 and 165°C at a depth of about 6km. Developing a geothermal system within this former hydrocarbon reservoir is quite challenging, not only for the temperatures, but also because of the important overpressures recorded in this reservoir. The possibility of dealing with a geothermal doublet in this context is clearly complicated by the overpressures, that are in the order of 170 kg/cm3 to the surface, requiring more complicated technological solutions. The other possibilities, like using a single borehole heat exchanger, has some problems with the economics, as in this case the life of the geothermal well is strongly reduced due to the limited interaction with the heated rock mass. In order to develop a proper study, we developed also a detailed 3D geological model for evaluating the characteristics of the aquifer and create some scenarios about the potential position of the injector and the producer in this geothermal doublet.