Does Fracking Cause Earthquakes? Formula Calcs Quake Size
Does fracking cause earthquakes? MDN has covered various stories in the past on this topic. It seems likely that injection wells (not hydraulic fracturing, but the wastewater from fracking being injected deeply in disposal wells) in some locations have been tied to earthquakes in some areas. Notably, when injection wells in Arkansas stopped pumping pressurized liquids into the wells, earthquakes in the area all but stopped (see this MDN story). It certainly seems there is a cause and effect situation.
But what about fracking a single well? Is there a danger that fracking can cause earthquakes? Arthur McGarr, a geologist at the US Geological Survey in Menlo Park, California has worked out a formula for predicting how large an earthquake can result from pumping/injecting fluids underground, including fracking fluids. He recently presented his formula at the annual meeting of the American Geophysical Union in San Francisco, CA. McGarr subsequently spoke to the journal Nature about his formula:
“If you inject about 10,000 cubic metres, then the maximum sized earthquake would be about a magnitude 3.3,” says McGarr. Every time the volume of water doubles, the maximum magnitude of any quake rises by roughly 0.4. “The earthquakes may end up being much smaller, but you want to be prepared for the worst-case scenario,” says McGarr. The relationship is straightforward, but it is the first time that anyone has quantified it, he adds.*
For a frame of reference, 10,000 cubic metres is 2.6 million gallons. It takes at least that much to frack a shale gas well, sometimes double that volume. But not all of that liquid is forced down at once when fracking—it’s staged over time.
Perhaps most importantly, McGarr says his formula does not predict how likely an earthquake is to happen, that “depends on other factors, such as the strength and permeability of the rock.” Shale is a very strong, tightly-packed (low permeability) rock, meaning earthquakes from fracking are not at all likely to happen when drilling a single well.
*Nature (Dec 9, 2011) – Method predicts size of fracking earthquakes
I would like to second Wacoyaco’s post on GasFrac. The advantages are so profound both environmental and financial that the inertia against changing from hydro-fracturing will be overcome despite the huge investment companies have in hydro-fracturing technology. Chevron,for one is using Gasfrac on 20 plus wells in Colorado and Husky Oil signed a three year contract to use Gasfrac for their wells. It seems Gasfrac is in negotiation with another unnamed large oil company as well. Gasfrac fractured wells are being evaluated for long term flow rates by several dozen companies they have done fracking for. Results are generally not released for competitive reasons but Seaview Energy released results in their third quarter 2011 Corporation presentation [ pg. 11 online ] showing LPG fracturing by Gasfrac produced wells 3TIMES as productive as wells Seaview did using hydro and oil fracturing in the same field. Other examples showing similar superior results are public.
Addressing the article on the risk of earthquakes from hydro-fracturing, it is worth noting that a typical well requiring 2.6 million gallons of water would require only 6 hundred thousand gallons of LPG for the same job. If the risk of an earthquake is related to the volume of fluid used , it would seem logical that LPG fracturing presents a much smaller risk profile.
This is just the beginning. This business will prove to be more detrimental as time goes on. Will it be too late?
You are wrong that fracing does not cause earthquakes. Earlier this year, two small earthquakes (1.5 amd 2.3 M) were caused by fracing the Presse Hall 1 well in Blackpool, Lancaster England. This has been confirmed both by British Geological Survey and the well operator, Cuadrilla Resources. Once the fracing stopped, so did the quakes. That said, this seems to have been a one-off. In the USA, of the dozen or so wells with induced seismicity, all were injection wells. Most were disposal wells, although a few were secondary recovery or geothermal. This does seems to be a minor problem. Most quakes were small. Generally the more fluid injected the larger the quakes, with the maximum around magnitude 5. Also the vast majority of injection wells are aseismic. Once the pumping stopped, so did the quakes. Therefore the simple way to control this is just to cap the few injection wells that cause a problem. (Not that I remember a single US operator who has ever admitted that their disposal well caused a quake.) Nevertheless injection is the primary route of flowback disposal, so you could say that fracing is the indirect cause of quakes, few and small though they be.
I would concur with your analysis Brian. My point is that fracking in a shale geology almost never (perhaps never) causes earthquakes, and as you point out, it is injection wells were there is a direct cause & effect. Since the flowback comes from the fracking process, you could say fracking is related, but that’s a stretch, because if you were pumping straight water into the same injection wells under the same pressure it would have (I would argue) the very same result. So it’s not the fracking of individual wells that is the issue, it is pumping massive amounts of liquid into some injection wells that are located in certain geologies that is the real issue.