An Overview of Retrofitting Abandoned Petroleum Wells for Geothermal Energy Production

Abstract

Abstract Geothermal energy is considered a reliable, sustainable and abundant source of energy with minimized environmental impact. The extracted geothermal energy may be utilized for direct heating, or electricity generation. The main challenge to access this energy is tremendous capital expenditures required for drilling and completion. Therefore, this work discusses and evaluates retrofitting abandoned petroleum wells to geothermal as a commonly proposed solution to the mentioned challenge. There are many oil and gas wells globally which are not used for production, injection or other purposes. Well abandonment is commonly considered as an essential measure to ensure safety and integrity of these wells, bearing huge costs and concerns for the petroleum industry. By converting abandoned or non-activated oil and gas wells to geothermal wells, it is claimed to be possible to produce geothermal energy and generate power. As a crucial stage for the claim verification and evaluation of feasibility or efficiency of this conversion, it is important to be aware of the practical and simulation case studies. Therefore, in this work, this work presents a comprehensive overview and analysis of 20 case studies published from different countries, followed by important downhole and surface parameters. As for the downhole characteristics, production scenarios either open-loop or closed-loop, optimization of open-loop systems, borehole heat exchangers with their different types and dimensions, and insulations are covered. Next, surface cycles including organic Rankine cycle (ORCs), selection of circulation fluids, flow rates, and working fluids are covered, followed by produced and net powers with evaluation of coefficient of performance (COP) and thermal efficiency. This investigation shows there is good potential for producing geothermal energy from abandoned and non-activated petroleum wells.