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Fracking: shaken, not stirred

Author : Alan Franck, Editor, Hazardex

19 February 2016

On February 13, a magnitude 5.1 earthquake hit northwest Oklahoma, the third strongest earthquake on record in the state, which has seen a notable increase in seismic activity since 2008. In addition to the increase in the number of earthquakes, Oklahoma has seen an increase in the severity of earthquakes in recent years, and some experts have warned that it is only a matter of time before an earthquake of potentially fatal magnitude strikes.

Stock image
Stock image

Scientists and environmental groups point to the state’s oil and gas industry as the main cause behind this increase in seismic activity. Specifically, they point to the disposal of salty wastewater that comes up as a by-product of hydraulic fracturing, which, when injected into underground wells along fault lines, has been linked to the spike in earthquakes.

According to political blog, a Stanford study released last year stated the amount of wastewater injected into underground disposal wells in Oklahoma has roughly doubled over the last two decades, and in three areas of the state that have seen the greatest increase in earthquake activity, the increase in wastewater disposal was even more marked.

These disposal sites are located near the the Arbuckle formation, a 7,000-foot-deep sedimentary formation located in central Oklahoma that also happens to sit directly above a rock layer that covers Oklahoma’s main fault zone. The researchers speculate that an increase in wastewater injection has increased the pressure placed on those fault lines, causing the fault lines to slip more easily, which in turn has lead to an increase in earthquakes.

In an effort to counter this trend, the Oklahoma Corporation Commission, which oversees oil and gas production in the state, has told frackers to reduce the amount of waste water that they inject into underground disposal wells. The Oklahoma Supreme Court also ruled in 2015 that those suffering material damage as a result of the seismic activity could sue oil and gas companies.

But so far, these measures do not seem to have changed the companies‘ behaviour. There is as yet no evidence that wastewater reinjection is being scaled back, according to US environmental groups including the Sierra Club, which has started a lawsuit to ensure companies take measures to reduce the risk.

Many other countries across Asia, South America and Europe are considering developing fracking industries, but in some of these, observers are worried that Oklahoma-type situations mean the problems could outweigh the benefits.

The UK offers an alternative pathway. Here, environmental regulators insist wastewater is removed for treatment and when clean, returned to rivers.

When exploratory fracking activities near Blackpool in 2011 were linked to two mild earthquakes in the area, the Government froze all fracking activities for 18 months while research was carried out into the risk.  

A report co-authored by the British Geological Survey based on that research concluded that those earthquakes were induced by fracking activities at the Preese Hall well, operated by Cuadrilla Resources. The report also concluded that further small earthquakes could not be ruled out, however the risk from these earthquakes was low and structural damage was extremely unlikely.

Report recommendations included:
*  Less fluid should be injected during future hydraulic fracture treatments. Since, the number of earthquakes should increase roughly proportionally to the injected volume, injecting less fluid should reduce the probability of larger earthquakes. Also, the fluid should be allowed to 'flow back' out of the formation after the hydraulic fracture forms, to minimise the probability of fluids percolating.
*  Earthquake activity should be carefully monitored before, during and after fracture treatments. If any earthquakes above a certain magnitude threshold occur, the operations should be temporarily suspended.

In countries where governments are keen to develop their shale oil and gas resources, the careful approach to risk adopted by countries such as the UK seems more likely to contain and overcome the increasingly well-organised opposition to fracking than that seen in Oklahoma.

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