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  • Writer's pictureThe Heat Beat

Let’s Talk About Seismicity.

By Jamie C. Beard, Esq.

Photo credit: Provided by Bob Worrall. Showing the Basel well, with the President of the Swiss Federation speaking to reporters about the project.

The future of geothermal is looking pretty darn good. Energy and engagement abound these days on the topic across the oil patch, from operators to oil service companies. Startups are popping up, often with oil and gas veterans at the wheel, and are off to the races with innovative scalable geothermal concepts. Funding entities are taking notice of the fresh blood and energy in the space. Once dubbed “the forgotten renewable,” you find geothermal springing up frequently these days in the media. Deep dives, like David Roberts’ excellent and well-researched piece in Vox last month, have spun off self-sustaining conversations, with new entities and faces showing up on the scene on a near daily basis.

If you know me, you likely well know that I am a vocal advocate for truth telling about the externalities of renewables. We need dispassionate and fact based analysis about each clean energy source, removed from special interests, lobbying, bias and preconceptions. For solar and wind, that means taking a strong look at the less than pristine supply chains, rare earth mining, end of life recycling, extreme weather resiliency, environmental footprint and wildlife impacts – not to mention intermittency and cascading externalities associated with grid-scale energy storage. For geothermal, high cost is a big drawback – which I believe will be addressed in the near term with targeted initiatives to drive down cost, and oil and gas industry partnership/engagement. The elephant in the room on geothermal in my mind is seismicity risk.

Last week, a geothermal (hydrothermal) project, still in its construction phase in Strasbourg France, produced a 3.8 magnitude earthquake. I’d been waiting on the right time to throw this article into the ether – it appears the time has come.

I’ll start off by saying that I find it remarkable how this article in Forbes published a few days ago, after the France event, treated the topic of seismicity. The article casually used the words “man-made earthquakes” at the end of a paragraph, as if an afterthought, with no further comment or explanation. For those in the geothermal community thinking hard about the implications of events like Strasbourg, this was surprising. My guess is that the public isn’t going to regard man-made earthquakes as a sidebar, particularly those who are impacted directly, or worried they will be.

The fact of the matter is humans have a limited attention span. The issue of geothermal related induced seismicity has floated around popular culture in a more direct way in the past, near in time to high profile seismicity events. But we have forgotten again. Let’s not leave it to another major event to get things moving in industry on this issue. It should be front and center, and everyone engaged from industry, to government and startups, should be organizing and thinking about it. Not about how to react when and after it happens, but how we can leverage what we know to make sure it doesn’t happen as we enter a geothermal drilling boom over the coming decades. We need to own the risk, and work to proactively prevent and mitigate. Fortunately, like most of the obstacles facing globally scalable geothermal concepts, it’s a challenge that can be met by leveraging learning and knowledge from the oil and gas industry.

Let’s take a closer look at where we’ve been on seismicity and geothermal so we can consider better where we are going. This week’s seismicity event in France isn’t the first rodeo for seismicity in the industry. Take this 5.4 magnitude quake in 2017 in Pohang South Korea, and this 3.4 magnitude quake in Basel Switzerland in 2009 as memorable recent examples. Geothermal and seismicity are correlated, even in natural systems. It is the man-made aspect of engineered systems that becomes a concern. Whenever we fracture rock in the subsurface, whether for oil and gas, minerals or geothermal, we create induced seismicity. In most cases, it is at a level which can be detected only with sensitive instruments. But sometimes, it makes the evening news.

I tracked down one of the folks, an oil and gas industry veteran now retired, who worked on the Basel well. Here are his reflections on the day of the earthquake:

“The rig’s mud pumps had been rigged to inject cold Rhine water into the top of the casing. The objective was to pump the water into the naturally fractured granite to open the cracks. These would be mapped with micro-seismic. The size and geometry of the natural fracture system was unknown. Small amounts of water (micro-fracks) was pumped to measure fracture initiation pressure and injectivity, and to calibrate the micro-seismic monitoring system, and to ascertain in which direction the opening of the natural fractures would propagate We then gradually ramped up the rig pumps to start opening up the fractured zone.

The distribution of the magnitude of micro-seismic events during such stimulations had been extensively studied. Based on these statistics a procedure was developed, in close cooperation with the Swiss Seismological Service, to stop injecting where certain statistical thresholds were reached. This would be at seismic moments far below what could be detected on surface. These statistical thresholds were reached, and pumping was stopped. The pressure was then slowly allowed to decay through the natural fractures, which took many hours.

The day of the now infamous 3.4 seismic event, I was in our office in Prattein, about seven miles from the rig. It sounded like a pistol shot from the next street. We bled down the pressure on the well after the event, and the project was later terminated. It was rare experience to be involved in an event which makes international news in a non-celebratory way. It was hard for me to comprehend the magnitude of the forces we had released, including their lasting impact on the nascent geothermal industry in the years to come. Over the next few years, a veritable cottage industry emerged dedicated to writing papers on seismic risk. It seemed to me than it would be a couple of decades before the scientists figured out some way to make geothermal safe, and to rebuild public trust and engagement in the space, so I went on to do other things. As an aside, the Wiki for Basel provides more background. A hindcast was made by RMS and is listed as reference 1. A fascinating document.

Thinking back on the event it seems to me that, when pushing the boundaries of technology at “the bleeding edge”, you occasionally cross those boundaries. This is human nature. Usually this is in the lab, or at the test track, and no publicity is generated. I wonder how many iPhones caught fire when Apple (striving to maintain technological leadership) was stretching the power system to enhance computational speed, or battery life, or reduce the profile in a closely fitting pair of jeans. Regretfully drilling and fracking are semi-public activities. It is hard to hide a deep drilling rig within the town boundaries.”

So what do Basel, Pohang and Strasbourg have in common? All signs point to the injector wells.

“My experience has been that most injectors end up getting operated above fracture propagation pressure - not by design but just as an observed fact,” noted Lance Cook, former Chief Scientist of Wells and VP of Technology at Royal Dutch Shell. He explained that in a Gulf of Mexico Deepwater TLP, two years or so after water injection started, to match withdrawals and maintain reservoir pressure (they had been experiencing subsidence at the sea floor from the massive volumes produced), they ended up breaching the mudline with injected fluid, even though they were intending to inject below frack pressure. “That water had to come a long way up past some pretty permeable zones to breach the mudline,” he said. “Injectors on autopilot are a big risk in my book. Injecting above frack pressure gets you real nice oil production responses on offset producers, but you lose control on where that fluid goes. In geothermal, that means losing fluid to faults – which results in seismicity risk.”

The Strasbourg event registered a 3.8 in magnitude. Let’s put that into perspective for a moment. 3.0 is not large enough to be felt by humans, but it is quite large by hydraulic fracturing standards in the oil and gas industry. Typical seismicity events within the oil and gas fracking context register negative on the Richter scale, equivalent to someone bouncing a basketball from across a field, or the vibration of an 18 wheeler driving as measured miles away. That said, seismicity within the oil and gas industry isn’t a non-issue, and there is significant data, monitoring and understanding within the industry that has pushed understanding about the circumstances that result in seismicity.

Let’s pause for a moment to consider the differences between the use of hydraulic fracturing to produce oil and gas, and its use to enable geothermal concepts like Engineered Geothermal Systems (EGS). In oil and gas, fracking entails pumping a mixture of water and sand with some stabilizing chemicals into shale, then pumping the mixture back out. The sand props the created fractures open, allowing hydrocarbons to flow. In geothermal, rock fracturing is typically performed with water injection, without chemicals or proppants, and the objective is to create more fractures and to connect existing fracture networks. The contexts are outwardly similar, but functionally very different. Here’s a key point that we will revisit later: fracking for oil and gas is performed (with the exception of deep disposal wells) in sedimentary rock. Fracking for geothermal is often done in basement formations, or igneous rock, as a way to widen or enhance existing fracture networks in those systems.

Dr. Ken Wisian, Associate Director at the Bureau of Economic Geology at UT Austin, and Associate State Geologist of Texas, described that in general, most induced seismicity in the oil and gas context appears to be due to salt water disposal – the injection of saline waste water from oil and gas production back into the ground. However hydraulic fracturing, the process of creating fractures in the subsurface via hydraulic pressure in order to stimulate oil and gas production, is also significantly correlated. “It does vary a lot between basins and in some, fracking is a dominant cause of induced seismicity. There is also fairly tight temporal correlation of seismicity with the onset both activities.” Dr. Wisian points to the TexNet seismicity catalog as a good reference point.

Seismic events in active injection operations in oil and gas range up to about magnitude 3. In Texas, where oil and gas activities largely occur in rural areas far from population centers, events of even the higher end of this magnitude often go completely unnoticed. But in populated areas, or under population centers, as Pohang and Basel indicate, events that would go unnoticed in rural areas can cause damage, fear, and spell the end for geothermal projects.

Marit Brommer, Executive Director of the International Geothermal Association, based in the Hague, agrees. “A seismicity event of 3-4 may not be considered a big deal in a rural area in Texas, but the reality at least in Europe is having a 3.4 quake near a population center linked to geothermal is very bad for our sector as a whole.” Indeed, since the Strasbourg quake, Fonroche (the project developer) has been asked to shut down operations, and permanent closure of the project is on the table.

But it may be that these events, while occurring in entirely different places in the world, all have elements in common that will allow proactive avoidance of seismicity events in the future. One of the primary commonalities is injection into granite or Hercynite (granite-like) basement rocks. And, as a correlation to oil and gas industry experience, many of the earthquakes experienced in Oklahoma prevalent in the news are the result of water injection into deep basement formations. “One thing we can say for sure from an industry perspective is that injection into igneous, faulted basement rock is much more risky than fracturing sedimentary rocks,” says Dr. Mukul Sharma, Professor of Petroleum Engineering at the University of Texas at Austin. “We need to draw on our industry experience here and seek to locate early EGS projects where seismicity events are well understood and bears less risk. That is in sedimentary rocks.” Dr. Sharma noted that the oil and gas industry has conducted well over a million fracture treatments in sedimentary rocks, and with a relatively small handful of exceptions, has not seen experienced seismic activity that is detectable by humans. “If this were a pharmaceutical drug trial, it would count as an incredible success.”

There is a point to make on standardization and process that will be necessary as we embark on our “green drilling boom” over the coming decades. There is an urgent need to identify geological pre-existing conditions and best practices, develop reservoir maps and map faults, design and convert best practices into design and engineering procedures, monitor systems in real time, and leverage data analytics to predict and constantly improve. We are in luck, since this is another area where the oil and gas industry can shine in bringing experience and expertise to the table. The geothermal sector created and implemented an induced seismicity protocol (basically an operating framework and guidance) in 2013, but this framework needs to be updated to reflect the many types of geothermal concepts being pursued, new developments and experiences from the field, and the technological reality of today’s drilling and production capabilities. The oil and gas industry players who are readying engagement in geothermal should fully engaged with, and even initiate, this exercise.

As we have discussed in a prior article on HeatBeat, the decentralized, local and low volume nature of geothermal development does not provide the robust cross-project collaboration and support needed to identify patterns and set best practices and robust and enforceable standards based on new learnings. ABS and DNV are a natural fit to play a role here as oil and gas industry leaders in safety standardization. API is another entity mentioned by industry leaders who is well positioned to quickly engage, provide thought leadership and lead the process of setting standards for industry engagement in geothermal.

Along these lines, our quickly developing knowledge of the role of injector wells and wellbore pressure in seismicity events should be turned into pro-active preventative action for future projects. “It is my opinion that injection of fluid above fracture propagation pressures should only occur under permit, and that exceeding fracture pressure without a permit should come with heavy fines and possible criminal penalties if done intentionally,” says Cook on the topic of industry standardization for geothermal development. In Oklahoma, the seismicity issues related to deep disposal wells in granite were significantly resolved with focused attention and thought from industry researchers and leaders. Cook points to the work of Dr. Mark Zoback at Stanford, and the fact that he and his team’s recommendations have been implemented in Oklahoma, as an example of the success industry has had in leveraging knowledge and implementing standards to prevent seismicity events. “We need enforceable injection standards for geothermal projects, now.”

For a nascent energy source like geothermal, trembling houses and concerned citizens will ground projects before they ever launch. The next headline making event near a population center could derail the industry entirely. We are at the cusp of embarking on a new gold rush – boom times in drilling and production of geothermal energy. Increased engagement in this space by new players will mean that entities may push the limits as competition increases, crossing the lines of unacceptable risk. One can imagine a situation, similar to frack ban movements, where a high profile seismicity event might lead to a push for across the board bans for geothermal concepts as a knee jerk reaction, regardless of whether they utilize fracking, or pose seismicity risk. The closed loop geothermal club is often vocal about this worry. Wildcatting, the very culture that could bring on our geothermal renaissance could also well be its downfall without careful, purposeful planning, and industry leadership.

Still, many in industry are optimistic (as am I) that this challenge will be met by oil and gas players, particularly given the body of knowledge from which oil and gas will draw on in approaching this problem set. Helpful also is the fact that multiple entities appear poised to enter the geothermal scene through sedimentary basins, on the way to the more difficult to crack igneous rock. “I know we can use what we know in oil and gas to prevent these problems,” Cook offered. “Efforts in Oklahoma prove that, but we need to be proactive, and meet it head on.”

Hey all you oil and gas brains out there - what do you think?

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