Going geographical with geothermal

robust materials for tools and equipment. Nevertheless, the base infrastructure already exists for implementing geothermal solutions.

Many engineering disciplines and skills translate directly from oil and gas to geothermal technology. Engineers with expertise in well integrity management, corrosion and erosion, wellbore management, and root cause analysis, for instance, have relevant experience for geothermal projects. They even use the same digital tools for modelling and analysing well performance. Fracturing and stimulation is another area of expertise transferrable to the geothermal sector. Engineers use these tools to open hydraulic communication between wellbores and access that thermal energy.

Figure 1. Drilling performance improvement at FORGE.2

Figure 2. Geothermal technologies applicable in the UK.3

The future of geothermal energy

One of the current challenges for geothermal is that the low installed base capacity means that the industry does not yet benefit from economies of scale and technology development. Costs of production range between US$66 and US$75/MWh, but these could drop by 20 to 30%, reaching <US$60 or even <US$50/MWh by 2030.¹

Governments are also contributing to the development of geothermal technology by making funds available. In the US, the Consolidated Land Appropriations Act passed in 2020 seeks to ease access to federal land for renewable energy. It establishes a goal of 25 GW of nameplate capacity and an annual budget of US$170 million for research and development. From a current base of under 4 GW capacity, there is a significant opportunity for growth in the geothermal market in the US alone.

With this in mind, THREE60 Energy is collaborating with Professor Silviu Livescu’s Sustainable Geoenergy Research and Engineering Laboratory at the University of Texas at Austin in the US. This initiative aims to accelerate the development of geothermal solutions and create a platform for the migration and application of oil and gas expertise. A key deliverable from this collaboration will be a software tool for analysing a building’s heating and cooling needs and proposing technical and economic geothermal solutions.

Some geothermal projects in Europe are already co-producing heat for buildings from oil and gas wells. Future opportunities include the potential conversion of oil and gas wells from depleted fields into geothermal wells, thus making use of existing infrastructure. This step may require deepening and repurposing of the wells, along with modifying tools and equipment for the higher temperatures.

Global effort in geothermal technical progression

There are multiple initiatives in play across the world energy business with regard to specific geothermal considerations. In the US, as well as the University of Texas at Austin as already noted, there has been the formation of the Texas Geothermal Alliance (TGA) and the continued progression also being made at the DoE funded Frontier Observatory for Research in Geothermal Energy (FORGE). Europe and many other parts of the world have similar efforts underway, all of which will support addressing a number of the fundamental challenges of geothermal energy and particularly enhanced geothermal systems (EGS), which will need to be resolved for economic scale power generation to be achieved. The SPE has also newly formed a Geothermal Technical Section, in order to harness the engineering body horsepower in support of this delivery.

Of these challenges related to delivery from drilling, one aspect stands out high on the agenda – the achievable rate of penetration (ROP) in these granitic and hard-rock environments given that high-angle wells are required. Recent work from Texas A&M (for FORGE) has demonstrated that a controlled physics-based process applied to PDC bit design has delivered an 80% improvement in ROP (see Figure 1). This translation of oil and gas workflows to the geothermal arena will continue to help make significant inroads.

With the completion and stimulation, the requirements for multiple advances across a range of challenges is just as daunting. For example, the components and materials that are required to prepare wells will need to operate in a very different envelope (350˚C - 450˚C); combine this with the cyclic (temperature) nature of the operations themselves, and integrity/functionality becomes a major issue. While development and advancement of the functional envelopes will occur, it is typically being initiated through government energy sector seed-money. This encouragement is required in the absence of market scale to initiate technical advancement – as the scope for geothermal in all its forms grows, there will be an increasing industry uptake. The same can be said for the EGS aspects, and it can already be seen that many of the lessons that have been learned in unconventional oil and gas have corresponding areas of application in the EGS environment.

Finally, surface aspects associated with the multiple processing approaches should not be underestimated. Such processes include dry-steam, flash-steam, and binary-cycle power stations. The majority of such systems present low efficiency <15% and the bulk of global plants <10%. This current inefficiency presents a huge opportunity to the industry to consider a swathe of solutions to moving that by factors of two or more. The true strength of surface-processing will be where the range of offtake and applications can be maximised. So, principal function power generation, then stepping down through to agricultural (greenhouse) heating, for example, as the power-fluid is cooled prior to return to the system. In addition to the plant efficiency considerations, there are also the chemical aspects that will need to be taken into account. Various scales, depositions, and potential for NORM will need to be assessed on a case-by-case basis, and much like in the oil and gas industry, the area of flow-assurance will be one that will need to be directly incorporated into the overall production system.

While the challenges are many, they are also great opportunities and directly reflect similar learning-curves that the oil and gas industry has repeatedly demonstrated an ability to traverse effectively.

A growing geothermal footprint

THREE60 Energy is well-positioned to play a part in expanding geothermal energy use. The company’s capabilities cover design, operations, maintenance, and process engineering in addition to subsurface geology, geophysics, reservoir, geomechanical, and petrophysics expertise. The company’s global footprint has opened doors for its involvement in projects all over the world, such as a current conceptual project with a major national oil company in South East Asia, as well as various projects in locations such as the UK, Scandinavia, and the US.

References

1. NREL, Geothermal Rising, ‘2021 US Geothermal power Production and District Heating Market report’, (2021). 2. DUPRIEST, F., and NOYNAER, S., ‘Drilling Practices and Workflows for Geothermal Operations’, (March 2022) 3. TOWNSEND, D.H. et al., ‘On The Rocks – Exploring Business Models for Geothermal Heat in the Land of Scotch. in 20’, (2020).

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Georgia Ainscow, Reddie & Grose, UK, outlines the role of geothermal in the green energy mix, highlighting its potential to support other renewables with its ability to operate consistently at a high availability rate.

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