Are earthquakes caused by water injection commonly employed in hydraulic fracturing operations? Is seismicity caused by the hundreds of oil disposal wells that are scattered throughout shale ranges in the U.S. and Canada? It’s not simple to answer those questions, but a recent Oklahoma supreme court ruling allows individuals to sue oil companies for earthquake damages.
Can Fracking Cause Earthquakes?
Yes, hydraulic fracturing can cause earthquakes but the difficulty will be in proving that hydraulic drilling is the sole cause above the natural movement of the earth. Hydraulic fracturing comes in many forms, among them:
- Water flooding.
- Low-pressure disposal (base rock or other formation disposal).
- Land use of high-pressure injection (offshore-style) disposal.
Oklahoma hydro-drillers are using the latter high injection techniques that had previously only been used in offshore formations causing more suspicion that the higher pressure drilling is causing the earthquakes. Regulatory agencies should enforce their existing rules that the frac gradient not be exceeded. (Microseismic geophones can be situated in wellbores close to where the water is being injected into shale wells. The hydraulic fracture propagations are then mapped to note the geological effects of the hydraulic drilling).
A hydraulically-induced fracture is technically considered a mini-earthquake. When small volume water injection methods are used, the earthquake intensity are considered negligible. It’s when the offshore high-volume, high-pressure methods are used that the frac gradient will be exceeded resulting in fracturing of the underlying rock formations (along lineaments, fault zones, fractures or cracks). These deeply buried lineaments are jostled by these high pressure injections of saline-chemical hydraulic fracturing fluids.
Don’t Frackers Replace the Oil They Take With Water?
The oil industry has traditionally injected water to replace the oil they took out of the ground. But given that water injection is a cost, and regulation and oversight is usually lacking, it’s variable whether any individual driller is conscientious about putting the same volume of water back given that all that water simply cuts into the bottom line. And even if a driller used the same high pressure to put the water back as they used to pull the high-pressure oil, the density and viscosity of oil and water are very different and would settle in the ground differently.
But Fracking Isn’t the Sole Cause of Earthquakes
As mentioned earlier, it’s still quite difficult for a person to prove that an earthquake was caused by fracking. Many states now have sink holes due to water table depletion, and residents in states that border the ocean (California, Florida, North Carolina …) have found salt water in their wells because the fresh water tables are lower than the ocean. Oklahoma has been draining their water aquifer for some time now and residents have had to dig their wells deeper to reach fresh water. The earthquakes could be the result of the earth settling from water table depletion, ahead of a giant sinkhole forming. Then there is also the fact that drilling oil from the ground will increase the size of that sinkhole, but who is responsible when two parties are culpable in contributing to the problem? Fracking can also be ruled out as a cause if the earthquake originated at a much deeper depth (miles) relative to where the fracking was taking place. Because this earthquake issue is so open to interpretation, both the prosecution and the defense will each be able to find geology experts that agree with their position, making the entire issue difficult to settle in court.