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Man-made earthquakesMan-made earthquake risk reduced if fracking is 895m from faults

Published 9 March 2018

Fracking – or hydraulic fracturing – is a process in which rocks are deliberately fractured to release oil or gas by injecting highly pressurized fluid into a borehole. This fluid is usually a mixture of water, chemicals and sand. The risk of man-made earthquakes due to fracking is greatly reduced if high-pressure fluid injection used to crack underground rocks is 895m away from faults in the Earth’s crust, according to new research.

The risk of man-made earthquakes due to fracking is greatly reduced if high-pressure fluid injection used to crack underground rocks is 895m away from faults in the Earth’s crust, according to new research.

The recommendation, from the ReFINE (Researching Fracking) consortium, is based on published microseismic data from 109 fracking operations carried out predominantly in the United States.

Jointly led by Durham and Newcastle Universities, the research looked at reducing the risk of reactivating geological faults by fluid injection in boreholes.

Microseismic data
Durham says that researchers used microseismic data to estimate how far fracking-induced fractures in rock extended horizontally from borehole injection points.

The results indicated there was a one per cent chance that fractures from fracking activity could extend horizontally beyond 895m in shale rocks.

There was also a 32 per cent chance of fractures extending horizontally beyond 433m, which had been previously suggested as a horizontal separation distance between fluid injection points and faults in an earlier study.

The research is published in the journal Geomechanics and Geophysics for Geo-Energy and Geo-Resources.

Hydraulic fracturing
Fracking – or hydraulic fracturing – is a process in which rocks are deliberately fractured to release oil or gas by injecting highly pressurized fluid into a borehole. This fluid is usually a mixture of water, chemicals and sand.

In 2011 tremors in Blackpool, were caused when injected fluid used in the fracking process reached a previously unknown geological fault at the Preese Hall fracking site.

Fracking is now recommencing onshore in the U.K. after it was halted because of fracking-induced earthquakes.