The state of Oklahoma has been subject to a sudden surge in earthquakes, with a report linking the rise in wastewater, caused by unconventional gas and oil extraction, as the root cause.
Fluid migration, from high-rate disposal wells used to extract water from excavation sites, causes earthquakes by creating underground fluid pressure that increases seismic activity.
Although thousands of these wells operate across the state, the report has linked earthquake activity 35km away to four of the biggest wells.
Numerous reports over recent years have made the connection between the injection of wastewater and quake activity – suggesting regulation and reform is needed to curb seismic activity.
A US Geological Survey (USGS) published January this year totalled the amount of manmade quakes across the US. In particular, the town of Jones, which is nearby to a large amount of disposal wells, was subject to 2,500 quakes since 2008.
Water is a natural factor in the energy extraction industry. It is not only used for hydraulic fracturing, but also for obtaining more oil from conventional wells.
When gas or oil is released from the ground, water tends to be either with it or close by. Separating that water from the fuel is crucial – the method is called ‘dewatering’.
Four of the largest wells in Oklahoma have been pumping 4 million barrels a month underground to a depth of 3.5km – creating huge pressure points.
The team that conducted the report connected the huge seismic activity around the town of Jones to the vast injections of water made by the larger wells.
The study’s lead author, Dr Katie Keranen, from Cornell University, said, “It is possible that pressure looks to have risen in the places where the earthquakes are occurring.
“That pressure increase is what we see in natural triggering. So, if a fault is close to failure, the amount that the pressure is going up at these locations in our model is enough to push them over the edge.”
Fears of similar seismic activities happening in the UK from fracking have sparked opposition to the increasing use of unconventional gas extraction.
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