Texas has recently experienced an unusual seismic event: over 100 earthquakes within a span of just nine days.
This sudden spike in seismic activity is particularly surprising for a region that is generally considered seismically inactive.
Experts are attributing this surge in earthquakes to oil and gas extraction activities, especially shale fracking and enhanced oil recovery (EOR).
In response, the Railroad Commission of Texas has idled two wells involved in deep saltwater injection to mitigate the seismicity.
The Phenomenon of Texas Earthquakes
On a recent Monday, three earthquakes struck West Texas, an area with a sparse population, adding to the dozens of quakes recorded in less than two weeks.
Among these, a magnitude 4.9 earthquake stands out as one of the most significant, tying for the eighth-strongest in the state’s history.
This rash of over 100 earthquakes in nine days is highly unusual for Texas, a state not typically prone to such seismic activity.
Oil and Gas Extraction’s Role
Texas is renowned for its extensive use of shale fracking technology, making it the leading state in shale gas extraction in the United States.
Experts, including Justin Rubinstein from the U.S. Geological Survey, assert that these earthquakes are “almost 99% likely” to be linked to local oil fields.
Rubinstein confidently states that the seismic activities are related to oil and gas extractions. Consequently, state officials have proactively idled two wells responsible for deep saltwater injection in an effort to reduce seismicity.
Shale Fracking and Saltwater Disposal
Shale fracking, a modern oil and gas extraction technique, involves drilling both vertically and horizontally into oil formations.
During this process, large volumes of water, sand, and chemicals are pumped into the ground at high pressure to create microfractures in the rock, allowing oil and gas to flow more freely.
However, this process also releases significant amounts of ancient, highly saline water trapped alongside the oil and gas.
Modern shale technology can access formations with a much lower oil-to-water ratio than in the past, often producing up to 20 barrels of salty water for every barrel of crude oil.
This oilfield brine, considered hazardous due to its high salt content and industrial compounds, is then disposed of by injecting it back underground. Texas currently has over 50,000 oilfield brine disposal wells.
Enhanced Oil Recovery (EOR)
Enhanced Oil Recovery (EOR) is another technique implicated in Texas’ seismic activity. U.S. oil production typically involves three phases: primary, secondary, and tertiary (enhanced) recovery.
The primary phase relies on natural reservoir pressure and artificial lift, recovering about 10% of the original oil.
Secondary recovery, involving water or gas injection, can recover an additional 20-40%. With much of the easily accessible oil already extracted, producers are increasingly turning to EOR, which can recover 30-60% or more of the original oil.
EOR involves methods like gas injection, chemical injection, and thermal recovery, with gas injection being the most prevalent in the U.S.
This technique uses gases such as CO2 to push additional oil to the production wellbore and reduce oil viscosity, enhancing flow. CO2 injection is notably used in the Permian Basin and other regions across the U.S.
Regulatory Response and Future Challenges
Regulatory bodies like the Railroad Commission of Texas are now tasked with addressing the seismic challenges posed by oil and gas activities.
Despite significant investments in carbon capture and storage (CCS) technologies by oil companies to offset CO2 emissions and facilitate EOR, the environmental and seismic impacts remain a concern.
Recent studies, such as the one by Calgary-based Menhwei Zhao, suggest that enhanced oil recovery could significantly extend the productive life of oil fields.
The U.S. Department of Energy (DoE) is actively researching new techniques to improve CO2-EOR’s economic viability and applicability to more reservoirs.
The DoE estimates that next-generation CO2-EOR could potentially unlock over 60 billion barrels of oil that would otherwise remain trapped.
Conclusion
The recent surge in Texas earthquakes underscores the complex relationship between oil and gas extraction techniques and seismic activity.
As the state grapples with these challenges, regulatory measures and technological advancements will play crucial roles in mitigating the impacts while balancing the demands of energy production.