Geothermal Well Conversion

Alaa Alahmed
November 21, 2023

Submitted as coursework for PH240, Stanford University, Fall 2023

Introduction

Fig. 1: Retrofitting Abandoned Oil and Gas Wells for Clean Energy (Courtesy of NREL and the DOE)

We can reduce greenhouse gas emissions and create a sustainable future for generations to come by converting abandoned oil and gas wells to geothermal wells. Geothermal power is an underutilized yet sustainable and renewable resource. This offers a renewable resource for generating electricity which can be done by incorporating a binary power plant through pumping water down the well to allow it to be heated by the rocks beneath the Earths surface as shown in Fig. 1. The extracted heat can be used directly or converted into electricity for many applications. The United States leads globally in the production of geothermal electricity, with nearly 3.7 GW in installed capacity. [1] However, such systems are associated with substantial upfront capital expenditure, which is a blocker towards investment and development.

Analysis

One approach to de-risk the significant upfront spending and reduce the overall geothermal project costs, is to utilize already existing infrastructure. Since the upstream infrastructure represents a large portion of the geothermal project capital expenditure, it is lucrative to consider retrofitting abandoned oil and gas wells for geothermal power generation. There are over three million abandoned oil and gas wells in the United States. [2] Such wells are associated with different designs, conditions, and subsurface conditions. They also come with smaller diameters compared to typical geothermal wells with typical power output in the range of 100-600 kW with an estimated lifetime of 10-40 years. [3,4] Considering a small number of 10,000 wells with an average binary power output of 350 kW, we evaluate the potential societal surplus expected from retrofitting oil and gas wells for geothermal power generation. As seen in Table 1, we find that retrofitting 100,000 wells to be geothermal power generators has the potential to supply power for just about 1.2% of the total electricity demand in the United States. In evaluating this idea, it is important to also consider the associated cost in comparison with alternative renewables. Here, major cost components include the binary power plant and interconnection capacity costs, which are estimated as $2300 kW^-1 and $130 kW^-1. [5,6]

Quantity	Numbers	Units
Number of abandoned wells	100,000	-
Power generation per well	350	kWe
Power generation for all wells	3.5 × 10⁷	kW
Energy generated per year	2.81 × 10¹¹	kWh
Average annual electricity consumption per capita	7,253.7	kWh
Number of people to serve	38,745,744	-
Percentage of served people	11.7	%

Table 1: Power Generation Calculations. [2,7]

Conclusion

In conclusion, the proposed geothermal retrofit on oil and gas wells has the potential to serve toward the transition away from fossil-based resources to renewable alternatives without disposing of existing infrastructure that is usable and has not fully depreciated. However, careful analysis needs to be conducted on well-by-well basis. Additionally, developers must consider the cost per unit power capacity associated with this approach compared to other renewable alternatives.

© Alaa Alahmed. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] T. Sharmin et al., "A State-of-the-art Review on for Geothermal Energy Extraction, Utilization, and Improvement Strategies: Conventional, Hybridized, and Enhanced Geothermal Systems," Int. J. Thermofluids 18, 100323 (2023).

[2] J. Jello and T. Baser, "Utilization of Existing Hydrocarbon Wells For Geothermal System Development: A Review," Applied Energy 348, 121456 (2023).

[3] R. Ashena, "Analysis of Some Case Studies and a Recommended Idea For Geothermal Energy Production From Retrofitted Abandoned Oil and Gas Wells," Geothermics 108, 102634 (2023).

[4] N. M. Wight and N. S. Bennett, "Geothermal Energy From Abandoned Oil and Gas Wells Using Water in Combination With a Closed Wellbore," Appl. Therm. Eng. 89, 908 (2015.

[5] K. F. Beckers and K. McCabe, "Geophires v2.0: Updated Geothermal Techno-Economic Simulation Tool," Geotherm. Energy 7, 5 (2019).

[6] M. J. Aljubran and R. N. Horne, "Fgem: Flexible Geothermal Economics Modeling Tool," Applied Energy 353A, 122125 (2024).

[7] S.-H. Yoo and J.-S. Lee, "Electricity Consumption and Economic Growth: A Cross-Country Analysis," Energy Policy 38, 622 (2010).