The Untapped Potential of Geothermal Energy

Presented by:

This article appears in the E&P newsletter. Subscribe to the E&P newsletter here.

Geothermal power generation is witnessing rapid growth worldwide, with installed capacity having grown by approximately 75% in the last five years. This has been aided by similarly rapid development of geothermal technology that can effectively generate power from relatively low temperatures, in turn increasing the number of viable sites including existing oil and gas production facilities. 

Geothermal energy can provide a consistent renewable energy source, in contrast to the intermittency of most other renewables. However, the capital expense and the risk of drilling wells to extract the geothermal energy are often seen as unattractive when compared with oil and gas investments.

There are also real challenges to pursuing the recovery of geothermal energy from existing assets, from the offshore location of many of the wells and parasitic pumping costs, to the aging condition of offshore platforms and scaling the technology for them. However, the major risks from drilling and exploration for geothermal energy are not applicable as the wells already exist and production is underway, that is, the risk has already been absorbed by the oil and gas companies.

The offshore energy landscape is increasingly diverse, with offshore wind turbines, electricity interconnectors, hydrogen electrolyzers, and carbon capture and storage all vying for space. We can expect the infrastructure to continue developing so exporting flexible on-demand electricity from geothermal as part of the energy mix back to shore could be a realistic possibility in the not-too-distant future.

In the meantime, continued extraction of fossil fuels is the reality of our short-term energy future. Blue hydrogen production requires natural gas and chemicals and plastics from oil are still necessary. In this context, an immediate action could be to decarbonize some, or all of the energy required for oil and gas production with geothermal energy.

The greenhouse gas emission footprint of oil and gas production is significant—a typical platform could require approximately 25MW electrical capacity, and this is usually met by using turbines fueled with natural gas. As the economic pressure grows from a strengthening carbon price, the cost of electricity increasing and regulator pressure to decarbonize operations, it would seem logical to review whether geothermal energy can improve operating costs and decrease greenhouse gas emissions.

To realize the huge potential of this untapped energy source, Shift Geothermal, a non-profit organization of respected academics and industry experts, has launched a bid to establish a new National Centre for Geothermal Energy in the U.K. The organization is seeking government and industry support to accelerate coordinated research and act as a catalyst for projects. It will identify and progress demonstrator and at scale projects and lobby for legislative and regulatory structures to establish geo-energy as part of the future energy mix. 

Clean geothermal energy can come in many forms with new and ground-breaking ideas continually being developed. In recent years useful amounts of power have been successfully generated at several oil and gas sites around the world. Crucially, the energy produced is not dependent on weather conditions and has a high capacity for electrical power output compared to other low carbon sources. 

The Organic Rankine Cycle is a technology that can convert a relatively low temperature heat resource to mechanical work and then electricity. While the name is cumbersome, it is the same process as a typical steam power cycle but, instead of steam, organic working fluids are used. An indicative efficiency of this technology currently is approximately 10% which, while seemingly underwhelming, is the equivalent of 68 of the largest offshore wind turbines in the North Sea alone. There is potential for this figure to increase as wells are not optimized to extract the greatest amount of geothermal energy, and the downhole equipment and higher efficiency energy cycles and surface plant required to do so are subjects of ongoing research.

Even when a well has reached the end of its economic life producing oil or gas, it can still have value as a source of geothermal heat as the downhole temperature of the reservoir is often still high enough. In this case, researchers have proposed alternative solutions including “closed-loop” geothermal systems negating the need for treatment or handling of produced water through surface hydrocarbon processing plant.

Alternatively, CO2 could be injected into the reservoir, thus driving out remaining petroleum in a similar way to water injection; this hot pressurized CO2 is in a supercritical state and could be expanded through a turbine to generate electricity. Though in its infancy, this concept shows there are novel ways to think about using existing infrastructure to harness both geothermal energy and sequester carbon dioxide. Success in developing technology that uses CO2 for power generation could see the storage of the greenhouse gas being commoditized on a large scale instead of it being solely a costly waste product.

The landscape to low-temperature power conversion is evolving and changes in efficiency can be possible with concentrated efforts to mature the technologies. An obvious parallel might be drawn with the solar industry - thin film solar cells were less than 10% efficient in the 1970s but can now achieve efficiencies great than 20%. The value of the opportunity is not purely the geothermal energy resource but also the knowledge and expertise developed over decades of subsurface engineering in the oil and gas industry. Further technology development is still required to turn this theoretical resource into a viable opportunity, but data shows the geothermal resource is too significant to ignore. 

A new National Centre for geo-energy would not only galvanize support for this burgeoning industry but act as a catalyst for research and test projects to scale geo-energy using oil and gas infrastructure, helping to secure jobs and opportunities for the supply chain.

Dr. Alison Auld is a mechanical engineer whose extensive knowledge of power generation and energy consumption has allowed her to work across industry, government and academia in practical delivery, advisory and research capacities. Her roles have included reducing energy consumption and GHG emissions across the Scottish malt whisky industry. She has also worked as a senior engineer for the U.K. government, a role which included exploring and evaluating innovation and providing technical support in the fields of unconventional oil and gas, geothermal energy, and industrial waste heat recovery.

While serving in Whitehall, Alison provided engineering and technical support to various teams within DECC and managed projects to provide evidence to inform future government policy decisions. Alison’s significant body of research on energy related topics includes pioneering work on the generation of electricity from coproduced fluids from oil wells which has informed much of the current development in this area.