Oklahoma's Earthquake Problem

Oklahoma’s Earthquake Problem

With the recent 5.8 Richter scale quake the state moved quickly to shut down 37 disposal wells in the Cambro-Ordovician Arbuckle formation. They also reduced water volumes in others. This zone near basement has long been known to have hydraulic links to basement faults due to its proximity to the Precambrian basement rocks. It has also long been known that fluid injection can make such faults slip causing tremors. Although most of those quakes have been relatively small and non-damaging, as we can see from the magnitude of this quake there is real reason for concern. As more fluid is injected into these zones the fluid injection pressures rise causing the fluid to move out further from the wellbore and toward potential contact with faults. If other quakes of this magnitude were to occur with more damage and human injury or even death there would be a humongous public outcry. The time to redesign fluid management and change well injection zones in Oklahoma, Kansas, Ohio, and other areas is NOW. This is not a sustainable situation. While oil & gas spokespeople and regulators can go on insisting the quakes are small and there is no cause for concern – clearly a 5.6 quake is a cause for concern. The current situation is not sustainable. Studies by the USGS and Stanford conclude that these deep injection reservoirs should be abandoned for shallower injection reservoirs. These areas also need to better maximize frack water reuse, although it is not only frack flow-back water but also produced water that is the issue. The current high volume production plays in the area – SCOOP, STACK (Merimac), Granite Wash, Cleveland, and others – apparently all produce significant amounts of water. Ohio has not had an injection well derived quake since the ones in 2011 in the Youngstown area – also associated with Cambro-Ordovician injection zones.

What is happening underground is now fairly well understood and can be mitigated. Unfortunately the deep near-basement injection zones are a big part of the problem. Seismic cannot image all faults and all areas are not covered with seismic anyway.  The history of the reaction to these quakes is also at issue: First the industry and state regulators denied that the quakes were even associated with injection wells. Although some may not be it is now quite obvious to all without a doubt that the wells are the cause. Next it has been pointed out repeatedly by the industry and regulators that the quakes small, shallow, and insignificant in terms of the damage they can cause. While that may be the case for the vast majority of them, no one really knows when a bigger one could occur causing real damage. Quakes caused by injection can cause significant damage and loss of life such as one the 7.9 earthquake in Sichuan province China that was attributed to a large reservoir and dam. Although there is some argument about reservoir-induced earthquakes, over 100 quakes worldwide have been attributed to hydropower dam reservoirs. The mechanism responsible for the Sichuan quake – increased fluid pressures in fissures and micro-cracks leading to deeper faults and lubricating them to slip – is basically the same mechanism as in the deep injection wells. That quake killed 80,000 people. With recent concern that the oil hub infrastructure in nearby Cushing, Oklahoma could be at risk, there is also reason to act quickly and decisively to alter water disposal practices in the area.  

Oddly, though Oklahoma has long acknowledged the obvious cause of the quakes, Texas has been reluctant to do so in the quakes, though much smaller, that have increased there as drilling and water injection has increased. In 2012 71% of produced water came from four states: Texas at 35%, California, Oklahoma, and Wyoming. The produced water comes mostly from conventional formations. In the northeast areas were the Marcellus and the Utica is produced, over 90% of frack flow-back and produced water is treated and recycled, to be used in subsequent frack jobs. Some companies recycle 100%. This is the highest area for frack water recycling in the U.S.  There is no reason this cannot also occur in in greater measure in the higher water producing states. According to consultant John Veil between 2007 and 2012 oil and gas production due to fracking increased by 20% but overall water production remained fairly flat. Conventional wells tend to produce more water over time but wells that produce from shale and other “tight” reservoirs tend to produce far less water and in contrast to conventional wells the ratio of water to gas and oil tends to drop over time. However, the initial flow back does produce a lot of water and so there have been more waste water injection wells drilled and more water injected since fracking vastly increased the amount of wells drilled overall. But the increase has been modest and future projections show only a modest further increase in injection. Recycling frack water and produced water costs money so operators in some areas have been reluctant to do it. Regulations could change that but would not be popular in the current downturn happening in the industry although that downturn may be winding down at present. 

References:

Search is On for Ways to Use Fracked Well Water, and Texas May Have an Answer – by Jeffrey Weiss, in Dallas Daily News, Sept. 7, 2016

Earthquakes Triggered By Dams – by International Rivers

A Fault Line Runs Through It – Exposing the Hidden Dangers of Dam-Induced Earthquakes – Factsheet by International Rivers