It didn’t take long for those who oppose Marcellus Shale gas drilling to try and link the recent earthquake centered near Mineral, VA on August 23 to hydraulic fracturing and horizontal drilling in the Marcellus. Blogs and internet forums said the 5.8 magnitude quake was a result of Marcellus drilling activity, but scientists have flatly stated there is no connection to be made: Marcellus drilling activity is not the cause of the quake. But is there ever a connection between shale gas drilling and earthquakes? The surprising answer is, maybe. But likely not what you think it is.
The holes drilled vertically and then horizontally, and the explosive charges used in hydraulic fracturing are so small relative to the earth and the tectonic plates upon which we live, that such activity has no bearing on earthquakes. However, the wastewater fluids from drilling is sometimes disposed of in what are called injection wells—deep wells built for the purpose of pumping millions of gallons of fluid—from oil and gas drilling as well as from other industrial sources—deep underground, where those fluids will stay for all eternity (or so the theory goes).
MDN previously wrote about several injection wells in Arkansas built near a seismic fault that are believed to be the cause of earthquakes in the area (see this MDN story). The theory is that the high pressure which is used to force the fluid into the wells deep underground forces the fluid into fractures that are causing the nearby fault to react and produce earthquakes. When the two companies operating the injection wells stopped pumping fluid into them, the earthquake activity went from thousands of small and some not-so-small tremors to almost none. It makes for a compelling case that those injection wells were causing the quakes.
However, in the case of the Mineral, VA quake, there are no nearby injection wells. The closest are six injection wells in Somerset, Clearfield, Beaver and Erie counties in central and western PA. Ohio operates hundreds of injection wells and takes most of the fracking wastewater from PA that’s not treated or recycled. There simply are no injection wells anywhere close to the earthquake on August 23.
So, nice try by those who oppose drilling. But you’ll need to look for a different argument as “triggers earthquakes” is not one of the results of drilling for natural gas in the Marcellus Shale.