Geothermal potential assessment for oil&gas fields in Italy

The decarbonisation of the energy sector is probably one of the main worldwide challenges of the future. The main contributors to the EU's greenhouse gas emissions today are heating and cooling systems. According to the literature, heating and cooling needs in buildings and industry account for about 50% of the EU’s energy consumption and only about 20% generated from renewable energy. In this scenario, oil&gas fields can be repurposed to produce geothermal energy, a secure, clean and renewable resource. The great amount of water stored in hydrocarbon reservoirs represents, now, a waste heat that can be used, thanks to the flexibility and wide availability of geothermal energy applications. The possibility of a crossover from oil & gas to geothermal energy production represents a chance to increase the share of renewable energy production and to reuse existing infrastructures but also to reconcile the social fabric with an industrial sector considered harmful to the environment. The most promising oil&gas fields for geothermal repurposing in Italy have been selected starting from the available information on fields and wells provided by the Italian Ministry of Economic Development, integrated with data retrievable in the scientific literature, and combined with the estimated temperatures at depth from the Italian National Geothermal Database. With this simplified approach, 42 fields have been identified at depths deeper than 2000-3000 m and with temperatures higher than 60-70 °C. However, harnessing the waste heat also of fluids at lower temperatures could have potential use for a variety of local direct geothermal applications. To produce a vision of the geothermal energy that could be recovered by repurposing the hydrocarbons fields on the Italian territory, this work has assessed the geothermal potential stored in five representative depleted oil & gas fields, which have been chosen among the selected most promising fields for geothermal repurposing. The volume method has been applied to these five representative fields to assess their geothermal potential. Then the technical potential has been estimated, assuming a value for the recovery factor, the efficiency and the life span of geothermal plants. This passage from geothermal potential to technical power is crucial to quantify the effective impact generated by the repurposing of Italian oil&gas fields into geothermal ones. The results are encouraging, although the applied method is preliminary and it has provided only a rough evaluation, which uses the data derived from exploration and production of hydrocarbons reservoirs, whose volumes may not coincide with the geothermal reservoirs. Those volumes may be greater and only an ad hoc analysis of the data collected by the owner companies of the existing fields and wells may produce a more precise evaluation.