By Dan Oancea

Small earthquakes triggered by drilling operations that inject liquids at depths higher than 2,000 – 3,000 m are well documented (read Related Articles).

Fracking is a natural gas (and oil) recovery method used in cases when the reservoir rocks hold a good amount of gas hosted in many tiny pores, fissures, pockets that need to be connected/stimulated in order to make for an economic recovery. That involves hydraulic fracturing of the rocks by injecting a mixture of high pressure fluids and sand which creates and maintain open fractures that would allow the gas or oil to freely move to the production hole.

Both processes (injection of spent brines and/or fracking) could trigger earthquakes (generally of smaller magnitude) if you inject those pressurized fluids in a fault system large enough to allow significant slip. At the same time the earthquakes could become significantly more powerful if you inject the spent brines at depths of at least 5,000 m (see Related Articles).

In the News: Texas earthquakes may be linked to wells for gas mining and Arkansas Earthquakes.