The rapid increase in the rate of earthquakes across the state of Oklahoma has been linked to wastewater disposal by the oil and gas industry in the region, according to a study by U.S. scientists published in Science last week.
Injecting polluted water in underground wells, a common practice for wastewater disposal adopted by many oil and gas companies, has been found to have caused a forty-fold increase in occurrence of earthquakes for a period of only five years. Although there are existing reports by scientists at the US Geological Survey and others, who have questioned the safety of the practice, this is the first study based on a thorough investigation.
Katie Keranen, an assistant professor at Cornell University and lead author of the study, together with her team, noted a huge increase in wastewater disposal in specific water wells in Oklahoma for the period between 2004 and 2008. Four of the biggest wells in the state now receive as much as 4 million barrels of wastewater per month, which is pumped to a depth of 3.5km. According to the scientists, who developed a model to estimate the wave of pressure from these wells, the disposal is most likely what has triggered more than 2,500 earthquakes of a magnitude greater than 3.0 in the area since 2008.
The use of water, not only for hydraulic fracturing but also for extracting as much oil from the wells as possible, has become increasingly common because of the drastic increase in oil and gas prices. In the urge to squeeze every little drop out, the industry is now using enormous amounts of water that have to be disposed of in accordance with numerous health and safety regulations. Injecting it underground seems to be the only reasonable solution, however as it turns out, it is just as unsafe as dumping the waste in rivers and streams.
The study met quite an opposition, of course, especially by New Dominion, the company owning the four wells. They claim that their premises meet all safety regulations and they also point out that their geologists and engineers have not been consulted by the authors.
In their defense, the authors explain that the situation is new and very likely not applicable to all wells. Nevertheless, the issue has to be investigated further so that the wells prone to high seismic activity can be outlined.
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