Repurposing abandoned oil and gas wells for geothermal energy extraction: A review of concepts, challenges, and opportunities

Repurposing abandoned oil and gas wells (AOGWs) for geothermal energy (GE) extraction has emerged as a promising strategy at the intersection of energy transition and environmental sustainability. This paper explores the economic, environmental, and technological dimensions of this innovative approach, aiming to provide further insights into its feasibility and potential impact. In terms of operations, a number of challenges were addressed in detail in converting oil and gas wells into GE sources mainly due to abandoned wellbore diameter, heat loss through the well column, low geothermal gradient, thermal facility cost, and unwanted entry of formation fluid into the well. However, accessing drilling data, well production history, and thermophysical and geological information of the reservoir could ease the conversion of AOGWs into GE sources, all while reducing operational costs compared to standard geothermal reservoirs. To prevent GE loss from abandoned wells, the potential applications of different methods such as in-situ combustion, use of horizontal wells, and increasing the depth of abandoned wells through drilling were scrutinized in terms of having favorable conditions to produce high-temperature fluid. Also, the application of simultaneous production of GE and hydrocarbon fluids from abandoned wells was addressed, enabling us the continued production of hydrocarbons alongside geothermal objectives. Results of this study in terms of detailing advantages, challenges, and practical experiences in converting AOGWs into GE sources could serve as a useful guide for decision-makers in the global oil and gas industry to use the subsurface geo-energy in a more sustainable way.