A sustainable approach to repurposing hydrocarbon wells for geothermal heat recovery in biogas production: The Irminio field case study in Italy

The climate change mitigation strategy includes the phase-out of hydrocarbon production. Before plugging and abandoning hydrocarbon wells, it is best to consider all available alternatives, such as reusing them for geothermal uses. This paper proposes a strategy for converting a hydrocarbon production site by repurposing existing hydrocarbon wells to harvest geothermal heat supplied to a biogas production facility. The case study is the Irminio oil field in SE Sicily, a favourable location for geothermal projects. A facility converting organic wastes into biogas with an anaerobic digester is sized to maintain the combined heat and power plant while feeding waste from pickup trucks. The findings demonstrate the feasibility of building two reactors that utilise 35,000 tons per year of organic waste, producing 596 m3/h of biogas. The plant footprint is limited within the existing oil area, which includes the CHP unit. The geothermal repurposing of existing wells will provide heating for the biomass that feeds the plant and a digester for 1.7 GWh/year, thereby preventing 312 tons/year of CO2 emissions. If the other productive or potentially productive wells in Italy are repurposed using a similar technique, the suggested strategy is expected to produce between 3 and 6 billion m3/y of green biomethane.