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Secrets of a Next-Gen Geothermal Company

Bastien Hermant – Lead Exploration Geologist

“Who knows how to swim through vast data sets?”

Episode 2 explores hydrothermal reservoirs vs. hydrothermal systems, flowing heat anomalies, the blind leading to brine and Angola’s underwater oil exploration as a conceptual model.

As we strive for a future powered by clean, abundant energy, TLS Tech Talks invites you to be a part of the conversation.

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Below you will find the complete transcript from Episode 2:

Rusty Muscarella: Hello and welcome to TLS Tech Talks Episode 2.1, today we are featuring Bastien Hermant, our Lead Exploration Geologist. Bastien, Thanks for joining us today, let’s start with you sharing a little bit about your experience in geology and where your inspiration came from to study it.

Bastien Hermant: Mmm, yeah. My first educational experience was at the engineering school in Nancy. Before that, I spent two years studying intensive mathematics and physics. Geology was relatively unknown to me then, aside from some high school teachings. 

During my time at the school, I chose to specialize in resource exploration and then geothermal energy. Geology, particularly high-temperature geothermal energy for electricity production, seemed like the best fit. 

I did an internship at TLS, seeking experience in high-temperature geothermal exploration. Since then, I’ve been working as an exploration geologist. Working alongside Mathieu Bellanger, a great geologist, has been incredibly educational. That’s why I’ve stayed for years, and I’m really happy to work here at TLS.

Rusty Muscarella: Beautiful. Next, can you tell us about geothermal systems compared to geothermal reservoirs?

Bastien Hermant: Yeah, it’s an important distinction. At TLS, we emphasize the difference between a geothermal reservoir and a geothermal system. The geothermal reservoir is the target, where you find hot water to produce electricity. In contrast, the geothermal system includes all aspects that produce the geothermal reservoir: where and how the heat anomaly induces hot water circulation.

Understanding the entire system is crucial because it helps determine the favorability of having a geothermal system and, therefore, a geothermal resource. We define a system as a combination of heat (the energy we’re looking for), fluid (the vector that transports this energy), and the drain or reservoir (where you find hot fluid circulation and storage).

You need all three components for a viable hydrothermal geothermal system. Other types of geothermal developments, like Enhanced Geothermal Systems (EGS) and Advanced Geothermal Systems (AGS), ignore some of these key elements. For instance, AGS focuses solely on heat, ignoring natural fluid and drainage/reservoir. Similarly, EGS focuses mainly on heat and attempts to build or improve the reservoir, then inject fluids.

However, with hydrothermal geothermal systems, which encompass most all current geothermal production, you need to consider all three key elements: heat, fluids, and the drain/reservoir. These are all very important.

Rusty Muscarella: Yep, nice. For TLS, tell us about TLS’s focus on identifying blind geothermal systems.

Bastien Hermant: Yeah, we think it’s important because several scientific publications in the western US show that most of the high geothermal potential is blind, meaning there are no surface manifestations like hot springs. For us, it’s obvious to focus on these blind systems because they represent most of the resource. It’s also quite challenging since you don’t have surface evidence, so you need to really understand how the system works. That’s why looking at geothermal systems is very interesting, because you know the key elements and what parameters influence these elements, allowing you to assess where you will find resources without relying on surface manifestations.

Not only surface manifestations but also data from previous exploration are important. Most resources, especially in the western US, were discovered thanks to hot springs or previous mineral and gas exploration. It’s really challenging to discover a truly blind system without anything on the surface.

Rusty Muscarella: Is this something that has been approached in the past but maybe the technology wasn’t available to identify, which is why there’s been a shift in focus?

Bastien Hermant: I think mainly because it’s easier to look for obvious resources. Potentially due to the lack of data in the past, but now with the number of projects, we have a lot of data, including regional data from geological surveys like the USGS and several universities producing strong datasets that help explore geothermal potential at a large scale. There’s a move in the geothermal community towards blind geothermal systems because we know they exist, they represent most of the resource, and we need to change the exploration parameters. 

At TLS, we’re working to discover these resources, much like the oil and gas industry did long ago. After finding obvious resources with oil seeps at the surface, the petroleum industry thought about the petroleum system and its key parameters to find resources, leading to huge discoveries offshore, like in Angola. There, you don’t have any oil seeps when looking at a resource beneath 2000 meters of water; it’s only based on the concept of the petroleum system. Similarly, in geothermal energy, we want to identify and understand the geothermal system’s key parameters to find resources based on a conceptual model.

Rusty Muscarella: So I guess this explains the unique process of TLS’ super top secret strategy to de-risk geothermal investments.

Bastien Hermant: The approach we use is quite new, and it’s founded on this exploration method. It leads us to focus on what we call the Crustal Fault Zone, a specific type of geothermal system that we believe is very ubiquitous. We can find it all over the world, and it has very high geothermal potential. It’s something we discovered in France, where we began our history at TLS. We have a project in the French Massif Central focused on Crustal Faults, but we also found this concept applicable in the US and many other countries. This led us to begin exploration in the US with new projects based on the Crustal Fault Zone system. 

We also developed artificial intelligence tools to help us manage and analyze the vast amounts of data we have, allowing us to rank which data are interesting and which parameters are crucial for assessing the system’s favorability. This has led to the development of machine learning and deep learning tools to evaluate geothermal potential and make the most of the data we have.

Rusty Muscarella: When you’re using this approach and technology, it’s data-heavy. Is data the only thing you integrate when choosing your prospects or locations?

Bastien Hermant: Obviously, there is still a geologist controlling the work done by our artificial intelligence software named DIG4GEO. The results of the favorability assessments are scientific, mainly based on geothermal potential. However, to develop geothermal power plants, we also consider other factors for economic viability. The first factor is the connection to the electric grid, which is crucial for project development. We map the electric grid and compare the results of geothermal favorability produced by DIG4GEO to create these maps, ensuring there is genuine economic geothermal potential.

Another important element is environmental stipulations. We want geothermal power plants to have the lowest possible impact on the environment. We carefully consider protected areas and regions with environmental stipulations because these can prolong project timelines and increase impact. By reducing environmental impact from the beginning, we make the project timeline more manageable. This conceptual approach to exploration helps us, especially in places like Nevada’s deserts, where hot springs indicate water and energy, leading to high biodiversity. Discovering blind geothermal systems far from hot springs allows us to develop viable power plants with minimal impact on local biodiversity.

Rusty Muscarella: How would you speak to the concept of abundance and the term durability, which we use as one of our parameters? Can you give us insights into how you calculate or understand the durability of hydrothermal systems?

Bastien Hermant: Yeah, there are several parameters to consider. First, we need to assess the volume of circulation we’re targeting, which involves understanding the cold water flow into the system. Next, we need to evaluate the amount of heat in the system since we’re extracting heat, not water, by pumping and reinjecting water into the ground. The main parameter is the heat, so we must model the heat entering and leaving the system. 

We do this through dynamic modeling, building geological models to simulate fluid circulation within the geothermal reservoir and fault zones. We can then experiment with different numbers of wells to see how they impact the resource in terms of temperature and fluid flow. The initial drilling and hydraulic tests from one or two wells, especially if we can connect them, will provide valuable data on the system’s dynamics. 

Conceptually, if the heat entering the system balances the heat we’re extracting, we can produce heat for a long time. However, geological systems can’t regenerate heat as quickly as we can extract it. The question is how long it will take before we see a decline in heat production. If the heat flow into the system is high, it could take hundreds of years to notice a decline. Conversely, if the system is small and we’re pumping too much, production and heat levels could decline rapidly.

Rusty Muscarella: I’ve heard of this occurring in other locations where durability was miscalculated. How do we monitor the flows and temperatures to track the impact on the heat source?

Bastien Hermant: Yes, monitoring fluid flow and temperature in each well is crucial. We also conduct tests between wells to determine how long it takes for water to travel from one well to another, which gives us information about the permeability and connection between wells. The model and production history will help us better assess the resource’s durability once we start producing. 

Rusty Muscarella: Yeah, I think like you said, there’s the science and the process at each stage of development to bring in the analysis and the proper tools to navigate efficiently and effectively the production of clean energy. In closing, can you share a bit about how you see the industry evolving and the scalability or real opportunities we are looking at with the success of our approach?

Bastien Hermant: I think we are at a key moment in geothermal exploration and for the geothermal community. People are increasingly aware that we need to produce more clean energy, and I’m sure that more and more people will become interested in geothermal energy because it has many advantages. Especially in the US, there is a lot of geothermal potential. So, I think the timing is great.

There are also efforts to develop other kinds of geothermal systems, like Enhanced Geothermal Systems (EGS) and Advanced Geothermal Systems (AGS). I’m looking forward to seeing what they will be able to produce, and it’s very interesting. However, I believe hydrothermal must remain the most interesting kind of geothermal energy because we know how to do it. When we discover something, we know how to produce clean energy from a viable geothermal system.

The key is our ability to discover the next blind geothermal system, and that’s where TLS excels. Our goal is to discover these systems through our conceptual approach and the technological tools we’ve developed to support this approach. I think this conceptual approach is highly scalable because once you understand the favorable parameters, you just need to find where these specific parameters exist elsewhere without relying on hot springs or other surface manifestations.

So, I think the timing is great for geothermal energy, and it’s also great for TLS to discover a lot of geothermal potential.

Rusty Muscarella: Beautiful. Yeah, I think we can continue digging into the approach that will allow us to identify these hidden sources. We also have a lot of technical processes to address, especially with our current projects in Nevada, with a major step being drilling. We’ll get to follow along as the process unfolds over the coming years and continue these conversations. If you have something else to share, we can continue, or we can say our goodbyes and share this conversation with the community interested in these clean energy opportunities and looking for solutions to some of our challenges.

Bastien Hermant: Just one thing I can share is that we are always open to sharing our knowledge and building strong collaborative relationships because the geothermal community is very small. We really need to help each other and bring geothermal energy to the place it belongs within the renewable energy landscape. For that, we need to build technological and financial partnerships to help each other develop projects. I believe there is enough space for everyone to develop their projects, including TLS and other companies. It’s important to keep in mind that we need to produce more clean energy to replace oil, gas, and coal plants. For that, we need to work together.

Sure, I think it’s part of my conviction to protect nature. I believe I am working towards that by having an impact on a global scale through producing clean energy at a more local scale. In France, particularly in the Pyrenees mountains close to Toulouse, it’s important to me. Sharing the real happiness of being in nature and witnessing its beauty is very important. It’s crucial to share this and teach people the importance of preserving nature.

Russ Muscarella: thank you listeners for tuning in, subscribing and commenting on our tech talks. Keep the questions coming and we will continue to share secrets from inside TLS. 

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Ep 2.1
Ep 2.2

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