Earthquakes have shaken Oklahoma forever, but seismicity (also read Quake frequency declines, seismic energy in Oklahoma climbs) picked up plenty of steam since 2011.
With the increase in quakes comes a lot of misinformation, and the U.S. Geological Survey is working to help the public separate fact from fiction.
The following information is from the USGS website.
• Fiction: Hydraulic fracturing — fracking — caused the increase in earthquakes.
• Fact: Wastewater disposal wells are the primary cause of an increase in earthquakes in the past several years. Wastewater disposal wells typically operate longer and inject more fluid than hydraulic fracturing. Enhanced oil recovery covers a variety of methods to produce oil and natural gas, including fracking, which happens in rock layers where oil and gas have been extracted. Wastewater often is injected into never-before-touched rocks, which can raise pressure levels more than oil recovery, and increases the likelihood of induced earthquake.
• Fiction: All wastewater injection wells induce earthquakes.
• Fact: Most injection wells are not associated with earthquakes that are felt by humans. Many factors combine for injection to induce earthquakes, including the rate of volume of injection, presence of faults big enough to produce felt earthquakes, stresses significant enough to produce a quake and presence of pathways for fluid to travel from the point of injection to faults.
• Fiction: Wastewater is only produced at fracking sites.
• Fact: All oil wells produce wastewater, not just fracking sites. Most wastewater is generated in the process of oil extraction and is found in nearly every oil and gas extraction well. Leftover hydraulic fracturing fluid, which is often included in wastewater, can be used in subsequent fracking operations.
• Fiction: Wastewater is all the same.
• Fact: The ingredients that make up wastewater are highly variable and often have little or nothing to do with hydraulic fracturing. Less than 10 percent of water injected into disposal wells in Oklahoma is fracking fluid. Most of the wastewater in Oklahoma is saltwater that comes up with the oil and gas in the extraction process.
• Fiction: Induced earthquakes always occur at injection sites.
• Fact: Induced earthquakes can occur at significant distances from injection wells, and at varying depths. Seismicity can be induced more than 10 miles away from the injection point and significantly deeper than the injection depth.
• Fiction: Injection wells require surface pressure to induce earthquakes.
• Fact: Wells that don’t require surface pressure to inject wastewater still can produce earthquakes. Wells where fluid is poured down the well still add pressure within the formation.