Disposal wells

According to the U.S. Geological Survey (USGS), each year there are millions of earthquakes across the world; however, most are undetected due to being in remote areas or being low on the Richter scale (usually below 2.0).

In the past 20 years, the number of known earthquakes around the world has been on the rise. The USGS claims that a partial explanation for this is the increasing number of seismograph stations and improvements in communication.

For example, in 1931 there were about 350 stations operating in the world. Today, there are more than 8,000 stations streaming data by electronic mail, Internet and satellite. The increase in data collection is helping researchers and scientists gain a better understanding of the complex issues as they relate to understanding naturally occurring and man-made earthquakes.

In the United States, disposal wells are regulated at the federal level as part of the U.S. Environmental Protection Agency (EPA) Underground Injection Control (UIC) program and known as Class II wells. There are approximately 144,000 Class II wells in the U.S., injecting over 2 billion gallons of brine (saltwater) every day. The U.S. EPA considers the deep injection of brine using disposals as the preferred and environmentally safe method for disposal of oilfield waste.

In Texas, the program is administered by the Railroad Commission of Texas (RRC) and follows national guidelines under the federal Safe Drinking Water Act for surface and groundwater protection. There are approximately 7,500 active disposal wells – nine operate in the Eagle Mountain Lake area where recent earthquake activity has occurred. Disposal wells have been operating in the area since the late 1960s.

The USGS has been studying disposal wells and earthquakes for decades. The vast majority of disposal wells operating in the U.S. have not caused earthquakes; however, research has found that at some locations the increase in seismicity seems to correlate with disposal wells. Some notable incidences include the Rocky Mountain Arsenal in 1961, and more recently the Northstar 1well near Youngtown, Ohio, in 2012. But researchers at the University of Texas have not been able to establish a link between certain disposal wells and earthquakes in North Texas. Researchers at Southern Methodist University are also conducting additional research.

Something researchers and industry regulators agree on is that more research and analysis is needed to better understand the cause and effect, especially in areas such as Eagle Mountain Lake, where previous historical activity and data is limited.