Mercedes Mullins
Fossil fuels are known to have a detrimental impact on the environment, contributing to air pollution, water pollution, and greenhouse gas emissions. In addition to these concerns, there is growing evidence that the production and extraction of fossil fuels can also induce earthquakes. This is particularly relevant in regions with extensive oil and gas extraction activities, such as Texas, Oklahoma, and other central US states, which have experienced a notable increase in seismic activity in recent years. The rapid injection of wastewater, a byproduct of fossil fuel production, into deep disposal wells is thought to be a key factor in triggering earthquakes. While most induced earthquakes are of low magnitude, there have been instances of larger quakes, such as the M5.8 earthquake near Pawnee, Oklahoma, in 2016, which was attributed to wastewater disposal. As such, understanding the relationship between fossil fuel production and seismic activity is crucial for assessing and mitigating the risks associated with human-induced earthquakes.
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What You'll Learn
Injection of oil field wastewater
Wastewater disposal is a separate process in which fluid waste from oil and gas production is injected deep underground, far below groundwater or drinking water aquifers. The United States Geological Survey (USGS) has identified that the injection of oil field wastewater into disposal wells can induce earthquakes.
The central United States has experienced a significant increase in seismicity over the past few years. Multiple studies have presented evidence that early to mid-twentieth-century earthquakes in Oklahoma and Texas were likely induced by fossil fuel production and/or injection of wastewater. Specifically, the 1952 magnitude 5.5 El Reno earthquake in Oklahoma may have been induced by deep injection of wastewater by the oil industry. The largest earthquake known to be induced by wastewater disposal was a M5.8 earthquake that occurred near Pawnee, Oklahoma in 2016. Stanford University studies have also shown that faults that lay dormant for millennia are now being activated by the injection of oil field wastewater into shallow disposal wells.
The fluid injected at depth is sometimes hydraulically connected to faults. When this happens, fluid pressures increase within the fault, counteracting the frictional forces on faults, making earthquakes more likely to occur. Even small pressure changes from wastewater disposal could be enough to disturb the delicate balance and set faults in motion. This is particularly true in areas where pressure remains high and faults are close to their stability limit.
While only a small fraction of disposal wells have induced earthquakes that are large enough to be of concern to the public, the risk of induced seismicity is still significant, especially if the storage is large in scale. The consequences of induced seismicity could disrupt pre-existing faults in the Earth's crust and compromise the seal integrity of the storage locations.
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Fracking and underground waste disposal
Fracking, or hydraulic fracturing, involves drilling a long steel pipe into the earth until it hits the ground layer containing oil or natural gas. The pipe then turns and extends horizontally, and a mixture of water, salt, sand, and additives (fracking fluid) is pumped through the pipe at high pressure to crack the underground rocks and release natural gas and oil.
While fracking has been linked to earthquakes, most induced earthquakes are not directly caused by this process. In fact, wastewater disposal is generally accepted to be the primary cause of the increased seismicity rate in Oklahoma within the past decade. Wastewater disposal wells operate for longer durations and inject much more fluid than hydraulic fracturing operations, making them more likely to induce earthquakes.
In Oklahoma, which has the most induced earthquakes in the United States, only 2% of earthquakes can be linked to hydraulic fracturing operations. The largest earthquake known to be induced by hydraulic fracturing in the United States was a magnitude 4.0 earthquake that occurred in 2018 in Texas. However, it is worth noting that before fracking began in Alberta, Canada, the area did not have a history of seismic activity.
Wastewater disposal is a separate process in which fluid waste from oil and gas production is injected deep underground, far below groundwater or drinking water aquifers. Of the 150,000 Class II injection wells in the United States, approximately 40,000 are waste fluid disposal wells for oil and gas operations, and only a small fraction of these disposal wells have induced earthquakes large enough to be of concern to the public. The largest earthquake known to be induced by wastewater disposal was a 5.8-magnitude earthquake that occurred near Pawnee, Oklahoma, in 2016.
Scientific studies have linked the majority of the increased seismic activity in the Central and Eastern United States to wastewater injection in deep disposal wells. Induced seismicity can also be caused by the injection of carbon dioxide as part of carbon capture and storage, which aims to sequester carbon dioxide captured from fossil fuel production in the Earth's crust. While safe practices can reduce the risk of induced seismicity due to carbon dioxide injection, the risk is still significant if the storage is large in scale.
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Human-induced earthquakes
Human activities can induce earthquakes, and fossil fuel production is one of the leading causes. The process of extracting fossil fuels, particularly shale gas, through hydraulic fracturing or "fracking," involves injecting high-pressure fluids into the ground to create fractures in rock layers and release natural gas. This process has been linked to an increase in seismic activity in several regions, including Texas, Oklahoma, and other central US states.
One of the primary concerns with fossil fuel production is the disposal of wastewater. The injection of wastewater from fossil fuel operations into deep underground wells has been identified as a significant contributor to induced seismicity. The rapid injection of large volumes of fluid can activate long-dormant faults, leading to earthquakes. This was evident in the case of the nation's biggest oil field, the Permian Basin oil field in West Texas, where the injection of wastewater into shallow disposal wells caused hundreds of earthquakes since 2014. Similarly, in 2016, a magnitude 5.8 earthquake near Pawnee, Oklahoma, was attributed to wastewater disposal, making it the largest earthquake known to be induced by this practice.
The central United States, particularly Oklahoma, has experienced a dramatic increase in seismicity in recent years. Studies suggest that the majority of significant earthquakes in this region may have been induced by the deep injection of wastewater by the oil industry. For example, the 1952 magnitude 5.5 El Reno earthquake in Oklahoma was likely triggered by wastewater injection. Additionally, the 2011 Prague, Oklahoma earthquake, with a magnitude of 5.6, has been linked to fossil fuel production and/or wastewater injection.
Induced seismicity can also occur due to the injection of carbon dioxide during carbon capture and storage processes. While safe practices can reduce the risk, the potential consequences of induced seismicity include disrupting pre-existing faults in the Earth's crust and compromising the seal integrity of storage locations.
Mining activities, separate from fossil fuel extraction, can also induce earthquakes. Mining affects the stress state of the surrounding rock mass, leading to observable deformation and seismic activity. These mining-induced events can pose risks to mine workers and infrastructure.
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Oil and gas extraction
In the process of oil and gas extraction, wastewater disposal is a separate process where fluid waste is injected deep underground, far below groundwater or drinking water aquifers. The fluid injected at depth is sometimes hydraulically connected to faults. When this happens, fluid pressures increase within the fault, counteracting the frictional forces on faults, making earthquakes more likely to occur.
The largest earthquake known to be induced by wastewater disposal was an M5.8 earthquake that occurred near Pawnee, Oklahoma, in 2016. Studies have also shown that since 2009, Oklahoma has experienced a surge in seismicity, with a rate of magnitude 3 and larger earthquakes exceeding California's from 2014 through 2017. These earthquakes have been induced by oil and gas-related processes, although few of these earthquakes were induced by fracking.
Hydraulic fracturing, or fracking, is the process of injecting wells with water, sand, and chemicals at very high pressure. This process creates fractures in deeply buried rocks to allow for the extraction of oil and natural gas, as well as geothermal energy. While fracking can cause small earthquakes (magnitudes smaller than 1), it has been shown that the recent increase in earthquakes in the central United States is primarily caused by the disposal of waste fluids that are a byproduct of oil production. Wastewater disposal wells typically operate for longer durations and inject much more fluid than is injected during the hydraulic fracturing process, making them more likely to induce earthquakes.
It is important to note that only a small fraction of disposal wells have induced earthquakes that are large enough to be of concern to the public. However, the risk of induced seismicity and its potential consequences, such as disrupting pre-existing faults in the Earth's crust, should be carefully considered and managed.
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Wastewater injection volumes
Wastewater injection has been linked to earthquakes in multiple studies. The process of wastewater disposal involves injecting fluid waste from oil and gas production deep underground, far below groundwater or drinking water aquifers. This method is used for the disposal of wastewater from conventional oil and gas extraction or hydraulic fracturing (fracking).
The central United States, particularly Oklahoma, has experienced a significant increase in seismic activity in recent years, with a dramatic rise in the number of earthquakes. Multiple studies have suggested that these earthquakes were likely induced by the injection of wastewater by the oil industry. The largest earthquake known to be induced by wastewater disposal was a M5.8 earthquake that occurred near Pawnee, Oklahoma, in 2016.
The link between wastewater injection and earthquakes is attributed to the increase in underground pressure. Injecting fluid quickly can induce earthquakes by rapidly increasing reservoir pressure over a larger area. The elevated pressure increases the chances of triggering a slip on a nearby fault that is already under natural stress. This is supported by the finding that disposal wells with higher injection rates, above 300,000 barrels per month, were 1.5 times more likely to be associated with earthquakes.
While most induced earthquakes due to wastewater injection are of low magnitude, there is still a risk of larger quakes. The potential consequences of induced seismicity include disrupting pre-existing faults in the Earth's crust and compromising the seal integrity of storage locations.
It is important to note that only a small fraction of disposal wells have induced earthquakes that are large enough to be of significant concern to the public. However, the inability to predict or anticipate when an injection activity will trigger an earthquake presents a challenge in managing this risk effectively.
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Frequently asked questions
Fossil fuel production can cause earthquakes through the injection of wastewater deep underground. This can activate faults located several miles below the surface, causing bigger earthquakes.
Studies have shown that the uptick in earthquakes in Texas, Oklahoma, and other central US states since 2009 coincides with the boom in hydraulic fracturing or "fracking".
Hydraulic fracturing involves injecting mixtures of fluid and sand deep underground at high pressures to extract fossil fuels. The injection of large volumes of fluid can change the stresses on nearby faults and cause earthquakes.
Yes, induced seismicity can also be caused by the injection of carbon dioxide as part of carbon capture and storage, which aims to sequester carbon dioxide from fossil fuel production in the Earth's crust.
Yes, safe practices and existing technologies can be utilized to reduce the risk of induced seismicity due to carbon dioxide injection. Additionally, high-quality data monitoring subsurface pressures, fluid injection volumes, and regional seismicity can help to understand and mitigate earthquake hazards.
