## 1 Introduction  
The policy visions of the 2030 UN Agenda for Sustainable Development and the Paris Agreement on Climate Change were both approved by the member states of the UN in 2015 and represent two fundamental contributions that guide the transition towards an economic model that aims not only for profitability but also for social progress and environmental protection. To achieve increased energy efficiency, all nations must change the ways in which they produce and manage natural energy resources in order to create more sustainable and environmentally resilient communities. The current Italian urban energy paradigm relies heavily on fossil fuels; given the air pollution and resource depletion caused by fossil-fuel use, this is unsustainable. Public and private investments in energy must be increased, especially for innovative technological models that transform the energy system, integrating renewable energy into end-use applications in buildings, transportation and industry. Geoscience offers solutions to this issue through the development of various options that could encourage decarbonisation and the transition to renewable energy sources at local and regional scales: electricity production from renewable sources, domestic heating/cooling using low-enthalpy geothermal energy resources and larger-scale technologies that target harmful emissions, such as bioenergy production and carbon capture and storage [1]. Geothermal energy is a weather-independent, environmentally friendly and currently available renewable resource; it represents an effective solution for power generation, heating and cooling, and direct-use applications. Specifically, energy production from available low- to medium-temperature geothermal resources associated with disused deep oil and gas wells in Italian oilfields has considerable potential. As a renewable energy source, it could solve problems associated with suspended wells near municipalities and allow for longer-term use of hydrocarbon wells, even at the end of their production cycle, which would benefit industry, civil and agriculture districts. According to [2], the variety of possible direct applications of geothermal resources in production districts, together with the corresponding temperature demand, is wide. It includes space heating, industrial uses, swimming pools, horticulture (especially greenhouses) and aquaculture. Studies have shown that hydrocarbon reservoirs and geothermal energy resources can coexist in sedimentary basin contexts because both have similar reservoir conditions [3; 4; 5]. Hydrocarbon resources are generated under specific temperature and pressure conditions in the source rocks, and groundwater is always involved in both the primary migration of oil from the source rock and the secondary migration of oil and gas to the reservoir. Consequently, oil and gas reservoirs in hydrocarbon basins act as geothermal reservoirs. Sedimentary basins have been explored for both oil and gas extraction purposes, so deep hydrocarbon wells are located in this geological context. Well logs, temperature distribution profiles and reservoir properties, such as depth to basement and geological formation thickness, are generally well known. Since 1985, 7246 wells have been drilled for hydrocarbon extraction in Italy, 898 of which are located onshore with varying operational statuses [6]. A variety of oil and gas reservoirs have been identified; geological and geophysical exploration campaigns into the deepest regions of such geological contexts have ascertained the coexistence of hydrocarbons and the low- to medium-temperature geothermal energy resources [7; 8]. Recent investigations have attempted to assess geothermal potentials, exploring deep geothermal resources in different regions and reconstructing heat flow maps at different depths [9; 10].