Fluid Pressue and Friction

in the Earth

Myths about Fracking

Myth #1: Hydraulic Fracturing (Fracking) is the reason that many areas like Oklahoma and Ohio have seen a large increase in earthquakes in recent years.

Fact: The act of fracking causes very small earthquakes by breaking up rock formations deep in the earth. These almost always cannot be felt on the surface of the earth. The cause of the increase in earthquakes in normally unconventional regions is due to wastewater injection.

Myth #2: Hydraulic Fracturing (Fracking) produces all the wastewater that is injected back into the earth.

Fact: Wastewater is produced during all oil and natural gas extraction processes. In Oklahoma, where a significant number of earthquakes have been observed, fracking only produces about 10%3 of wastewater that is injected into the earth. However, in other regions spent hydraulic fracturing fluid represents a larger portion of fluid injected into the earth.

Myth #3: All wastewater injection sites cause earthquakes.

Fact: There are hundreds of thousands of active wastewater disposal wells in the United States and only a few dozen3 have caused felt earthquakes.

Myth #4: Wells only induce earthquakes if the fluid is injected at high pressure.

Fact: Even wells injecting under gravity, where the wastewater is poured down the well without adding any pressure, still increase the fluid pressure in at the bottom of the well and can still induce earthquakes.

Myth #5: Wastewater disposal wells can only induce earthquakes in areas directly surrounding the well.

Fact: Earthquakes can be induced ten miles or more from the injection well and at much greater depths.

Myth #6: Induced and triggered earthquakes are the same.

Fact: Induced earthquakes refer to seismicity that is caused by a stress change that is comparable to the shear stress required for the fault to slip. Triggered earthquakes refer to seismicity that is caused by a stress change that is only a small portion of the shear stress required for the fault to slip. Induced earthquakes are present in regions that are not particularly prone to large amounts of seismic activity like Oklahoma or Ohio. Triggered earthquakes are present in regions that are more prone to seismic activity like California.

More information can be found in the following publication:

Rubinstein, J. L., & Mahani, A. B. (2015). Myths and Facts on Wastewater Injection, Hydraulic Fracturing, Enhanced Oil Recovery, and Induced Seismicity. Seismological Research Letters, 86(4), 1060-1067. doi:10.1785/0220150067 pdf

Mcgarr, A., Simpson, D., & Seeber, L. (2002). 40 Case histories of induced and triggered seismicity. International Geophysics International Handbook of Earthquake and Engineering Seismology, 647-661. doi:10.1016/s0074-6142(02)80243-1 pdf

Photo: http://www.pbs.org/newshour/updates/drilling-induced-earthquakes-may-endanger-millions-in-2016-usgs-says/