DEEP CLOSED LOOP GEOTHERMAL HEAT EXCHANGER AND ENERGY TRANSITION BY O&G WELLS REUSE

Since the end of the XIX century, many wells have been drilled worldwide for both Oil & Gas exploration purposes. Most of them are abandoned and minerally closed because of exhaustion or non-productive (lack of resources) status. In the new epoch of the energy transition scenario, the possibility of reusing them to exploit geothermal energy seems very promising. Considering that approximately 40% of the total costs for a new geothermal project could be devoted to drilling activity, repurposing abandoned oil and gas wells offers a wide range of applications. The drilled borehole available data (e.g., underground temperature, lithology, geophysical and core data) provide helpful information about the sub-surface reservoirs, reducing the mining risk level, and wells allow direct access to the sub-surface heat energy. However, to develop a commercially viable geothermal power/thermal generating system, one must consider several factors, i.e., available prospecting, drilling and reservoir technologies, energy costs in the area, and resource durability. This project examines the development and optimization of Deep Closed-Loop Geothermal Heat Exchanger (DCL-GHE) systems as a sustainable renewable energy solution, focusing on repurposing abandoned oil and gas wells for geothermal use. Through numerical simulations with Comsol Multiphysics, sensitivity analyses, and experimental data, the study explores the thermal and operational performance of innovative U-shape DCL-GHE systems across varying geological and geothermal settings in Italy. To improve the current understanding of the behaviour of this kind of geothermal technology, the present work investigates the long-term performance of a deep U-shape closed-loop system as a possible solution for reusing abandoned hydrocarbon wells. A multi-phase approach was used combining historical Oil & Gas exploration data analysis, numerical modelling and core sample thermal measurements. A case study of an oilfield located in northwest Italy, between the municipalities of Novara and Milan in the eastern Po River Plain, was analysed to investigate even the influence of hydrogeological conditions on system efficiency. This work may provide important information to bridge the gap in the existing literature, consisting on coupling numerical and real case study data by developing a clear and simplified procedure for assessing the feasibility of repurposing abandoned oil and gas wells for geothermal use and for evaluating the feasibility to apply deep closed-loop solutions as a new sustainable approach for clean energy production