Oklahoma Earthquakes and their correlation to Injection Wells

Correlating Oklahoma Earthquakes and Injection Wells

I got interested in the correlation of earthquakes to injection wells when, after hearing a report on the radio, I went to a favorite data source, Wolfram Alpha, and entered "Oklahoma Earthquakes 2004 to 2014." The sharp increase in the frequency of earthquakes recent years was striking. Below is my version of the  data.

Hypothesis: Earthquake locations and timing are correlated to injections wells.

Conclusions: The data below will show qualitatively that the correlations appear to be quite strong.
(Of course correlation does not necessarily prove causation).

Background Info

A collection of background a reference material I've found.
Here is an informative presentation on Injection Wells by an engineer at the Chesapeake Corp.
Real time tracking from Tulsa World.
Instructive video on fracking technology.
Here's a good video of a scientist at the USGS talking about her study.

Data sources

Well data

For injection wells apparently the Oklahoma Corporation Commission is in charge of permitting. Fracking is excluded from regulation as part of the 2005 Energy Policy Act.

I got the data from a Google Fusion Table available here.
Below is a heat map of the OK injection well data.

Earthquake data

Earthquake data is available from the USGS here.
To retrieve data I used the coordinates North 37, South 33.6, East 265.6, West 257. Later in my analysis I restricted data points to be within Oklahoma State borders

I searched back to 1970 and generally used data from Magnitude 2 or greater. This data is plotted  in the intro.

Correlation of Quakes and Wells

Time Correlation

The simplest data exploration is to look at cumulative earthquake and drilling permits.
As a proxy for the well date, I use the Last_MIT_Date for the well from the data, assuming the MIT (Mechanical Integrity Test) is done prior to but close to actual use.

The correlation is unarguably strong.

Geographical Correlation

The next thing to look at is whether the locations of earthquakes correlate to the location of heavy drilling activity.

Indeed there seems to be a high degree of correlation here as well. The heaviest concentrations of drilling activity are correlated with the highest density of earthquakes

Putting it together

We can put the time and location data together in the form of a .gif file. Each snapshot of the animation below  represents a time slice of about 6 months. (I intend to add dates to the animation later)

You have to look quick, but on the last time-slice of the gif the earthquake activity really spikes. This is also seen in the graph in the introduction. Cummulative analysis shows that the number of earthquakes between Jan2013 and Jun2014 more than triples the number of quakes in Oklahoma compared to the total number from Jan1970! There seem to be three big swarms, which will be a subject of further investigation.

It's important to note that the current of correlation of earthquakes and drilling, but itself, does not constitute causation. However, I agree with editorial write Wayne Greene that the correlation is strong enough that the drilling and oil exploration companies have some 'splainin' to do. Umbrellas don't cause rain, but if you see a lot of them, you're dang sure it's raining.

Clearly more disclosure of data will help protect business interests.