What do wastewater and earthquakes have in common?

Researchers predict that the second highest earthquake in Kansas between 2013-2016 resulted from the deep injection of wastewater from the oil and gas production. These earthquakes occurred in southern Kansas, frequently in Harper County and neighboring counties. Historically, the magnitude of earthquakes in southern Kansas where below 2.0. However, they peaked in 2015 with 51 earthquakes above the magnitude of 3.0.

For their study, they focused on Sumner and Harper County in southern Kansas. Oil and gas operation began in Sumner County in 1915 and in Harper County in 1950. This contributed 1 million barrels of oil and 1 billion cubic feet of natural gas in Kansas. However, oil production decreased between 1960 and 2010; while gas production remained constant until 2015, especially in Harper County, according to the authors. This interest resulted from the Mississippi Limestone Play that promised a plentiful source of natural gas to companies through hydraulic fracturing or horizontal drilling in Oklahoma and Kansas.  Wastewater disposal, typically, is deposited in the Arbuckle group, which is an aquifer that covers most of the state of Kansas. The Arbuckle group lies on the Precambrian basement that creates fractures and faults in the Arbuckle geological formation. Therefore, if water withdraws and wastewater injections disrupt Precambrian basement, this could lead to frequent earthquakes. Within this study area, there was a correlation between the highest total volume wells and the wells with most documented seismic activity. From their results, earthquakes appeared to lag 2 to 6 months after the wastewater injection.

To ensure their link between wastewater injection from oil and gas deep injection, Rubinstein  and his co-authors investigated if hydraulic fracturing led to seismic activity. They found that this possibility was low in this location because they did not spatially or temporally correlate in their results.

Rubinstein and his authors, also, found that They, also, found that the seismic activity in Kansas is parallel to the activity in Oklahoma which has a similar problem with frequent earthquakes. Recently, the rate of earthquakes decreased in Oklahoma and Kansas. The authors suggested that this was due to the economic and regulatory forces that prompted the decline in injection. In 2016, the Kansas Corporation Commission ordered the reduction of injection in southern Kansas. However, in future research, they will assess how other factors led to the decline in earthquakes.

Source: Rubinstein, J. L., Ellsworth, W.L., Dougherty, S.L. 2018. The 2013-2016 induced earthquakes in harper and sumner Counties, southern kansas. Bulletin of Seismological Society of America 20:20.

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