Geothermal energy could play an essential part in the world’s green-energy future. It can fulfil some of the primary global energy demands, help reduce greenhouse gas emissions and substitute hydrocarbon usage. Approximately 70% of geothermal resources globally are low temperature (typically below about 150 °C), but these are largely untapped. Some hydrocarbon fields, for example, could be suitable for low-temperature geothermal energy extraction. So, Rohit Duggal at Victoria University of Wellington, New Zealand, and colleagues carry out a comprehensive review of existing projects that utilise oil-and-gas fields for geothermal energy generation.
The review reveals that many pilot projects have been technically successful, but there are concerns. Estimates of resource potential for geothermal systems in hydrocarbons fields can be unreliable and the long-term performance of such systems is rarely discussed, yet these parameters are essential for the sustainable management of any field. Economic viability is also difficult to predict and is inhibited by the current favouring of the production of hydrocarbons over water, which lowers production rate and results in heat loss as the fluid travels up the wellbore. From a geological perspective, many bottom-hole temperature measurements are carried out soon after drilling completion, meaning the measured values do not represent true reservoir potential. However, accurate reservoir characterisation would provide more reliable estimates of reservoir capabilities, while numerical simulations of fluid flow, momentum and heat transport would provide a useful indicator of reservoir behaviour.
Many hydrocarbon fields possess existing infrastructure that could help reduce operating costs. They are also widespread globally, enabling access for countries without conventional high-temperature volcanic resources. The key to unlocking the potential of geothermal energy from hydrocarbon fields relies on a greater understanding of long-term reservoir behaviour during energy generation, allowing for more informed decision-making. Ultimately, interlinked economical, technical and geological parameters will influence the likelihood of a profitable development.
Kyle Watts
DETAILS: Renewable Sustainable Energy Rev. 154 (2022); doi.org/10.1016/j.rser.2021.111865
