Geothermal energy is considered a reliable, sustainable, and abundant source of energy with minimal effect on the environment. The extracted geothermal energy may be used for direct heating or for electricity generation. The main challenge to accessing this energy is the tremendous capital expenditures required for drilling and completion. This paper presents and evaluates the idea of retrofitting abandoned petroleum wells for geothermal energy production.
Many oil and gas wells exist globally that are not used for production, injection, or other purposes. Well abandonment is considered an essential measure to ensure the safety and integrity of these wells, resulting in huge costs and concerns for the petroleum industry. Converting abandoned or nonactive oil and gas wells to geothermal wells may allow for the production of geothermal energy and the generation of power.
Crucial to verifying this claim and evaluating the feasibility or efficiency of well conversion is the awareness of practical and simulation studies that have been already implemented.
This work presents a comprehensive overview and analysis of 20 case studies published from different countries, followed by important downhole and surface parameters. Downhole characteristics covered include production scenarios—either open-loop or closed-loop—optimization of open-loop systems, borehole heat exchangers with their different types and dimensions, and insulation. Next, surface cycles including organic Rankine cycle, the selection of circulation fluids, working fluids, and flow rates are covered, followed by produced and net power with an evaluation of coefficient of performance and thermal efficiency.
This investigation shows there is good potential for using geothermal energy from abandoned and old petroleum wells.