O&G earthquakes blight southern Kansas
Justin Rubinstein talks to Khai Trung Le about the study of Kansas earthquakes induced from oil and gas wastewater disposal.
Between 1973 and 2012, the state of Kansas, USA, experienced one magnitude 2.0 earthquake. Yet, between 2013 and 2016, 127 earthquakes of magnitude 3.0 and greater occurred, with 115 localised in Harper and Sumner counties. The seismic activity has long been linked with increases in oil and gas (O&G) activity in the state, and a recent paper from the US Geological Survey (USGS), The 2013–2016 Induced Earthquakes in Harper and Sumner Counties, Southern Kansas, is the latest research connecting the earthquakes with O&G activities.
Justin Rubinstein, USGS Research Physicist and Deputy Chief of the Induced Seismological Project, told Materials World, ‘With the rise in earthquakes in southern Kansas starting in late 2013, the USGS decided to use monitoring networks to try and understand the seismicity there. Examining this activity has afforded us the opportunity to understand the start of an induced earthquake sequence, and to examine a number of other aspects of it.’
The team looked at 6,845 earthquakes within Harper and Sumner counties between March 2014 and December 2016, finding that the upsurge in seismic events correlated in time and location with increases in disposal of wastewater, a byproduct of many O&G extraction operations. It is often dispensed with via deep underground injection for permanent sequestration, isolated from O&G reservoirs and drinking water aquifers.
The seismic activity recorded in the study is almost entirely localised in the shallow crystalline basement below the wastewater injection horizon of the Arbuckle Group at the base of the sedimentary section, increasing pressure in the rock pores and reducing friction among faults, setting off induced earthquakes.
The increase is statistically improbable to occur naturally, with Rubinstein making specific mention of the increase in magnitude 4.0 seismic events, from zero between 1974 and 2012 to six in the following four years, when injection started. ‘The probability of this rate change occurring randomly is around 0.16%’.
The increase meant Kansas held the second-highest earthquake rate in the central states, after Oklahoma, where a similar increase in seismic activity has also been linked to wastewater injection.
No on fracking
Rubinstein notes in the 2015 paper, Myths and Facts on Wastewater Injection, Hydraulic Fracturing, Enhanced Oil Recovery, and Induced Seismicity, also published by the Seismological Society of America, one of the most common misconceptions is that the seismic activity is rooted in hydraulic fracturing. Although not unrelated, with Rubinstein stating in the paper that while fracking is directly causing a small amount of induced earthquakes in the USA, most were the result of O&G wastewater disposal.
Similarly, not all injection wells cause induced earthquakes. A combination of events including faults and stresses large enough to produce felt earthquakes, the presence of fluid pathways from the injection points to the faults, and for that pressure to be large enough can induce earthquakes. Among the 35,000 active disposal wells in the USA, only a dozen are known to have caused seismic events.
On 15 February 2018, a Kansas House committee rejected a bill designed to prevent earthquakes caused by O&G wastewater. The bill was brought forward by the Kansas Sierra Club, a conservation, non-profit, and local homeowners organisation who have suffered property damage. Resident Cindy Hoedel testified, ‘The regulatory system has failed. [The Kansas Corporation Commission] mission calls for them to regulate the O&G industry to protect the public safety. They’re not doing it.’
The bill was rejected following lobbying by O&G interests, although Annie Kuether, Democratic member of the Kansas House of Representatives, conceded that earthquakes in the state were caused by O&G production, stating, ‘Two years ago, early in the morning, my 100-year-old house groaned, made a lot of noise, and shook with a very big earthquake. So it seems to me [that] we need to do more work with Oklahoma.’
However, Edward Cross, President of the Kansas Independent Oil and Gas Association, believed the bill was based on false assumptions, and driven by activists in political effort to disrupt the O&G industry. Cross said, ‘They offer ideas that are contradictory or otherwise separated from reality, and try to manufacture debate that confuses policymakers and the public with assertions that are out of context and need more information for a complete and informed discussion.’
The events have not been disastrous. The Michigan Technological University, USA, programme, UPSeis, describes magnitude 2.5 to 5.4 seismic events as ‘often felt, but only causes minor damage’. So far, no one has been harmed in the Kansas earthquakes. But with clear frictions between Kansas homeowners and the O&G industry, it is difficult to predict how the situation will be resolved.
Rubinstein said, ‘It’s hard to say how long it’s going to last, given that what we’re looking at in Kansas is a much higher rate of injection than in the places where seismicity slowed quickly. If they shut off all the injection, the decay could still take years, just because there’s been such a dramatic change in the regional pressure field.
‘A number of research groups are considering this problem using different approaches. They are built either on numerical simulations of the physics of injection and its potential for inducing earthquakes and purely statistical models. The USGS builds a statistical model with a one-year forecast, released every year since 2015.’
Groningen, the Netherlands
Kansas is not the only region to be struck by earthquakes caused by O&G activities. The Netherlands entered the world stage in 1959 when the Groningen field was discovered. One of Europe’s richest sources of gas, Groningen exported 84bl cubic metres of natural gas in 2013. However, minor earthquakes have struck the region since the 1980s, with the frequency and severity of seismic events escalating since 2011. Minister for Economic Affairs Eric Wiebes capped the volume of gas extracted at 21.6bln cubic metres in 2017.
An extensive campaign from local residents who have suffered significant damage from the earthquakes and green group Milieudefensie claim the Dutch government has been resistant to change. This is matched with resistance from the Council of State to the 2017 cap. In a statement, the Council said, ‘The minister has so far failed to properly substantiate his previous decision to allow 21.6bln cubic metres to be extracted annually over the next five years’.
However, on 8 January 2018, Groningen was hit by a magnitude 3.4 quake, the second strongest recorded above the gas fields and the largest in five years. As a result, Minister for Economic Affairs Eric Wiebes instructed 200 of the largest O&G interests in the area to cease sourcing fuel from the site. An ongoing lawsuit from 3,500 victims claims around 100,000 houses have been damaged in the seismic activity, losing as much as €1bln in value.
Some urge caution against making direct comparisons between Groningen and Kansas, including Utrecht University, Netherlands, seismologist Hanneke Paulssen, who said, ‘The earthquakes in Groningen are, simply put, caused by subsidence. The gas is removed and the earth starts to move. Fracking is a completely different technique, in which cracks in the rock are temporarily pressed open […] in general, the longer you continue with the extraction of oil and gas, the greater the risk of earthquakes.’
To read The 2013–2016 Induced Earthquakes in Harper and Sumner Counties, Southern Kansas, visit bit.ly/2tpkkTu