At the Seismological Society of America’s annual conference held in early May 2014, several studies examined whether there is a correlation between the injection of wastewater into disposal wells and seismic activity.
In an abstract entitled “Potential Case of Induced Seismicity from A Water Disposal Well in South-Central Oklahoma,” the researcher found that a swarm of earthquakes in Love County, Oklahoma beginning on September 17, 2013, were occurring at shallow depths consistent with the injection depths of a near-by injection disposal well.
However, because this area had seen similar shallow earthquakes in the past, the researcher could not address whether the earthquake swarm was caused by fluid injection or simply an “unlikely coincidence.”
In another presentation, seismologists at the US Geological Survey indicated that, while the total volume of wastewater injected into a disposal can be a factor in a seismic episode, another important factor “is the presence of high-permeability fluid pathways that can channel the injection effects on pore pressure from the target aquifer into a fault zone, especially a fault that is well oriented for slip in the ambient stress field.” Often, these faults are only revealed after the seismic incident. “The available data corroborate the notion that the likelihood of induced earthquakes large enough to be felt is largely independent of injection rate.”
It should be noted that previously, a representative of the Oklahoma Corporation Commission, who was reviewing the relationship between certain earthquakes and injections wells, stated that there was not enough evidence to say that the seismic events were caused by injection of oil and gas waste and urged everyone to keep an “open mind” regarding the cause of the earthquakes.
Also the causal connection between hydraulic fracturing and earthquakes continues to be unresolved – studies and experts have produced research and opinion on both sides of the issue. Oklahoma state geologist G. Randy Keller called the claims "a rush to judgment," while Interior Department Deputy Secretary David Hayes said his teams have found "no evidence to suggest that hydraulic fracturing itself" is the cause of earthquakes.
For additional information, please see “Injection Wells and Their Possible Link to Seismic Activity” and “What’s Shaking? Induced Seismicity.”
This post was written by Barclay Nicholson (firstname.lastname@example.org or 713.651.3662) from Norton Rose Fulbright's Energy Practice Group.