The Heat Beat
A Clean Energy Solution Fit for the (Frack) King
Mukul Sharma has quite a reputation in the oil and gas industry. A faculty member of the University of Texas at Austin’s Petroleum and Geosystems Engineering Department for the past 35 years, and National Academy of Engineering inductee for his significant contributions in the development of nonconventional oil and gas resources, he’s the guy oil and gas calls with its most complex problems – particularly if hydraulic fracturing is involved. Mukul is an international subject matter expert in fracking - the oil and gas methodology that has rearranged global geopolitics, while becoming a lightning rod in environmental circles. During a recent conversation with a friend in oil and gas, upon mentioning Mukul’s name, he responded with an enthusiastic outburst of Mukul’s apparent nickname in industry circles – a nickname that makes Mukul himself feel a bit awkward: The Frack King.
Given that the purpose of fracking is to maximize the production of hydrocarbons from the world’s sedimentary basins, why is an interview with an internationally recognized frack legend in a geothermal blog you might ask?
There are currently three major concepts in the running in the race toward globally scalable geothermal energy: 1) engineered or enhanced geothermal systems (EGS), 2) closed loop systems, and 3) hybrid approaches that combine elements of both. To develop an EGS project, wells are drilled vertically or horizontally, and an engineered “reservoir” is created in hot dry rock utilizing hydraulic fracturing. Fluid is then circulated through the system, where it heats up as it travels through the reservoir, and energy is produced from resulting steam on the surface. Since its inception, the scale of EGS has been extremely limited and successes few and far between due to challenges associated with poor connectivity and circulation of fluid through the engineered reservoirs, low flow rates, induced seismicity events, and reservoir short circuits. These are all problems related to the engineered reservoir that is created by fracking.
So you see where we are headed right? Enter the Frack King onto the geothermal scene. And oh boy y’all - this is another major score for the future of scalable geothermal energy.
Last week, Mukul launched a new geothermal venture called Geothermix, and has set out to tackle the obstacles standing in the way of EGS as a scalable clean energy solution. He aims to drill his first wells in the coming months, and leverage his robust relationships with oil and gas industry partners to build momentum for geothermal in the oil patch. I talked with Mukul to explore this exciting news. Our interview has been edited for length and clarity.
JB: There are many oil and gas entities out there who considered geothermal prospects a decade or more ago and counted it out. Why do you think geothermal deserves a hard look now?
MS: Traditionally geothermal energy has been sidelined as an energy source that was uneconomic and limited to very specific geographic locations where subsurface temperatures exceeded 250C or 300C. This was because vertical or deviated wells were used with one or two fractures resulting in limited contact area between the injected fluid and the rock. Today, with the experience we have gathered in drilling and completing thousands of unconventional oil and gas wells over the past 15 years, we can drill horizontal wells with 200 or more hydraulic fractures and increase the area available for heat exchange with the injected fluid by 100 times. This has the potential to increase the energy extraction rate in the EGS context by at least 10 times. This is a game changer that can make EGS projects commercially attractive.
JB: What specifically has changed that has made the resource interesting for oil and gas in your mind?
MS: Oil and gas companies are at their core, energy companies. They are interested in energy sources that have four key attributes: 1) they must be commercially viable, or have a clear path to near-term viability, 2) they must be scalable, 3) as a result of carbon neutrality commitments in industry, increasingly they must have a low, no or even negative carbon footprint, and 4) they must provide a reliable, baseload, uninterrupted source of energy. With the advent of horizontal drilling and fracturing, for the first time, geothermal energy, and more specifically EGS, has the potential to deliver all of these elements.
JB: What geothermal concepts interest you the most?
MS: The application of horizontal drilling and hydraulic fracturing has led to an energy revolution in the US in the past decade. I am most excited about applying these technologies directly to geothermal resources. With minor modifications, and leveraging some novel technology that we have designed specifically for EGS, it is possible to deploy and demonstrate the effectiveness of these ideas in the field in the very short term. We are shovel ready.
JB: You speak with a good deal of confidence about the application of oil and gas expertise and methodologies being the missing link in solving geothermal problems. What makes you so confident?
MS: My confidence stems from the extensive knowledge base and experience that the oil and gas industry has acquired over the past decade, and from my own personal experience with fracture design and execution in very tight rocks. When we started in the unconventionals space, there were a lot of issues that needed to be resolved, but over time we have increased well productivity by a factor of 4 to 10 in many shale basins. We are very early on the learning curve in the EGS context, but I have no doubt that we will be able to translate oil and gas learnings from the past decade, and successfully deploy these methods in EGS.
JB: Do you see the application of hydraulic fracturing in EGS concepts as a factor that will limit scale?
MS: I do not think this will be a limitation if we spend the time that is needed on community outreach and public education. It would be a huge mistake to abandon this valuable clean energy resource that has the potential to unlock gigawatts, even terawatts of reliable, clean, CO2 free and baseload geothermal energy.
JB: I often hear from NGOs concerns about fracking and geothermal, and indeed the term does carry baggage, regulatory obstacles, and public relations challenges in parts of the world. Can you explain the difference between fracking in the hydrocarbon and geothermal contexts?
MS: The primary concern that has emerged in the development of unconventional resources in the US is the generation of seismic events or earthquakes. These concerns are real, but they are primarily associated with high-volume water disposal wells, not hydraulic fracturing itself. The big difference between these water disposal wells and geothermal wells is that in EGS applications the water is being circulated from the injection well to the production well. Therefore, the fluid pressure in the earth should not increase significantly as the plant operates. This reduces the risk of seismic events dramatically. Other risks associated with hydraulic fracturing are minor as I point out in a presentation I had prepared about 10 or 12 years ago Hydraulic Fracturing: Facts and Myths. I think that perhaps the most obvious and important difference between fracking in the EGS and hydrocarbon contexts is the absence of extraction and subsequent burning of hydrocarbons in the EGS context. The end result is instead a high quality and ubiquitous clean energy source. I think this reframes the discussion and discourse around hydraulic fracturing entirely. We are entering the age of green fracking.
JB: Do you regard this difference as significant enough to justify a rebranding of the technology for geothermal applications? In other words, do we need to call fracking in the EGS context something different?
MS: There have already been efforts in the geothermal industry, and even in government circles to call hydraulic fracturing something different in geothermal contexts. For instance, you’ll see the terms “hydroshearing” or “hydro-fracking” or similar plays on words used in EGS related literature to describe the process of hydraulic fracturing without using the term itself. While there are some technical differences between geothermal fracking and fracking on oil and gas wells (for instance, thermal stresses and natural fractures can play a much more important role in geothermal fracking) – the fact of the matter is we are applying pressure to a wellbore in order to engineer the subsurface in both contexts. It is my personal preference to call a spade a spade, and instead of trying to rebrand hydraulic fracturing in an attempt to sidestep controversy, we need to be transparent about exactly what are we doing in the EGS context, how it differs from fracking in the hydrocarbon context, and what we get as a result of this technique – near limitless, scalable clean energy. I believe this transparency will go a long way in building trust as we work toward broad consensus across stakeholder groups about the future of scalable geothermal.
JB: I’m glad you raised the subject of seismicity. It is a hot topic in places like Europe where clean energy is all the rage, but fracking is not. What specifically do you think went wrong at Basel and Pohang, and what steps can be taken to avoid these EGS associated seismicity events in the future?
MS: It is well known that earthquakes or seismic events induced by fluid injection can occur in places where open wellbores and fluid-filled fractures intersect faults. Increasing the fluid pressure in these faults can result in the fault faces suddenly slipping past each other resulting in a seismic event. The vast majority of these events are so small as to be undetectable on the surface. However, there have been incidents in EGS wells and in oil and gas wells where larger seismic events have been recorded. There are several ways of minimizing the risk of fault reactivation at EGS sites (such as the events at Basel and Pohang): 1) Avoid geological areas with known faults. These faults are usually detectable using 2-D or 3-D seismic surveys and measurements while drilling, 2) Test and monitor the site with small-scale injection before commencing full scale operations. Micro-seismic signatures will indicate whether a larger event is likely, 3) Ensure good connectivity between injector and producer wells so that excessive pressures are not needed to circulate fluid through the EGS. These steps which require careful monitoring and analysis will reduce the already small risk of seismic events by orders of magnitude.
Let us keep in mind that for every Pohang or Basel there are thousands of hydraulic fracturing and water injection projects that have been conducted over the past 100 years with no associated earthquakes. Every human activity, flying planes, driving automobiles, or taking prescription medications has risks and rewards. No human activity has zero risks. As engineers and scientists it is our responsibility to maximize the benefits and minimize the risks and then make a conscious decision whether the rewards justify the risks. In the case of EGS, there is no doubt in my mind that the benefits far outweigh the potential risks.
JB: You have just launched a geothermal venture called Geothermix. Awesome news for geothermal! What’s the plan for your startup?
MS: The primary goal of Geothermix is to conduct a field demonstration of a novel EGS system. The work will be conducted in three phases. Phase 1 will involve site selection, well design and fracture design as well as a detailed simulation of the selected EGS site. Phase 2 will involve drilling and multi-stage fracturing at least two horizontal wells (preferably 3) and demonstrating our ability to connect and circulate fluid using our proprietary fracture designs and hardware. Assuming a successful demonstration of the EGS in Phase 2 (meeting pre-specified metrics), Phase 3 will involve building a 25 MW geothermal power generation facility.
JB: What is your timeline to drill your first wells?
MS: Once the project is initiated in Q1 2021, Phase 1 of the project is estimated to last for one year. We are planning to spend one year each on Phases 2 and 3.
JB: How is your startup engaging with the oil and gas industry?
MS: We are currently in discussions with oil and gas companies and others about potential sites that have attractive geothermal potential. I’d invite any companies who are interested in learning more to contact us. Oil and gas operators and service providers recognize that joining forces to explore the application of horizontal drilling and fracturing to geothermal systems is the most efficient way to demonstrate the feasibility and potential of this technology. We plan to build a core group of companies that will fund and lead the effort to apply some of the technological advances that the oil and gas companies have made to the geothermal arena.
JB: You are a National Academy of Engineering member for your significant contributions in the development of unconventionals, and an internationally recognized authority on a variety of topics in petroleum engineering. What role do you think the National Academies could play in helping support our coming geothermal renaissance?
MS: The National Academy of Engineering (NAE) periodically weighs in on issues that are of national and international importance. The development of a reliable, carbon-free energy resource certainly meets that criterion. At the next NAE meeting I will be bringing up the issue of geothermal energy and asking the NAE to empower a sub-committee to prepare a report outlining how the development of geothermal resources can be accelerated in the US. This may provide useful input to the DOE, DOD, NASA and other agencies that allocate resources to the development of cutting-edge energy technologies and energy transition generally. If we are to make the most of this incredible, ubiquitous, global clean energy opportunity, it will require broad support across all stakeholders in the near term.
Mukul M. Sharma is Professor and holds the “Tex” Moncrief Jr. Centennial Chair in the Hildebrand Department of Petroleum and Geosystems Engineering at the University of Texas at Austin. He served as Chairman of the Department from 2001 to 2005. His current research interests include engineered geothermal systems, hydraulic fracturing, oilfield water management, formation damage and improved oil recovery. He has published more than 450 journal articles and conference proceedings and has 21 patents. He can be contacted at email@example.com or firstname.lastname@example.org.