Predicting the thermal regime of the Po Plain subsurface (Italy) using geostatistical modeling constrained by legacy wells

Italy boasts a long history of hydrocarbon exploration. The Po Basin, in particular, has been extensively explored due to its peculiar geological setting, arising from the convergence of the Southern Alps and Northern Apennines. Because of this, substantial subsurface data have been collected and made publicly available. Today, data from past oil and gas exploration campaigns can find new life in decarbonization programs, especially for geothermal exploration. Geothermal data on the Po Basin, including bottom hole temperature (BHT) and drill stem test (DST) records, play a crucial role in understanding the thermal state of the subsurface, and can therefore be employed in the exploration of geothermal resources. This study presents a 3D model of the thermal regime in the Po Basin based on the analysis of legacy hydrocarbon wells. Geostatistical models of subsurface temperatures are produced via direct sequential simulations that consider: (i) the overall geothermal gradient across the region, (ii) anisotropy in the temperature field revealed by variogram analysis, and (iii) temperature data in the surrounding geological volumes. A base-case model of expected temperature values and associated conditional variance are thus generated from which depth-to-the-isotherm maps were extracted for temperatures in the low-enthalpy range (<100 °C). The study confirms that promising thermal anomalies are mapped in the Ferrara Arc and the buried Southern Alps. These areas offer opportunities for new developments and the repurposing of depleted oil wells for district heating. Additionally, the findings highlight other areas in the Po Plain (e.g., Emilian Arc) where there exists more subtle geothermal potential for further exploration and development.